static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
		       const struct io_uring_sqe *sqe)
{
	struct io_submit_state *state;
	unsigned int sqe_flags;
	int personality, ret = 0;

	req->opcode = READ_ONCE(sqe->opcode);
	/* same numerical values with corresponding REQ_F_*, safe to copy */
	req->flags = sqe_flags = READ_ONCE(sqe->flags);
	req->user_data = READ_ONCE(sqe->user_data);
	req->async_data = NULL;
	req->file = NULL;
	req->ctx = ctx;
	req->link = NULL;
	req->fixed_rsrc_refs = NULL;
	/* one is dropped after submission, the other at completion */
	atomic_set(&req->refs, 2);
	req->task = current;
	req->result = 0;
	req->work.creds = NULL;

	/* enforce forwards compatibility on users */
	if (unlikely(sqe_flags & ~SQE_VALID_FLAGS))
		return -EINVAL;
	if (unlikely(req->opcode >= IORING_OP_LAST))
		return -EINVAL;
	if (unlikely(!io_check_restriction(ctx, req, sqe_flags)))
		return -EACCES;

	if ((sqe_flags & IOSQE_BUFFER_SELECT) &&
	    !io_op_defs[req->opcode].buffer_select)
		return -EOPNOTSUPP;

	personality = READ_ONCE(sqe->personality);
	if (personality) {
		req->work.creds = xa_load(&ctx->personalities, personality);
		if (!req->work.creds)
			return -EINVAL;
		get_cred(req->work.creds);
	}
	state = &ctx->submit_state;

	/*
	 * Plug now if we have more than 1 IO left after this, and the target
	 * is potentially a read/write to block based storage.
	 */
	if (!state->plug_started && state->ios_left > 1 &&
	    io_op_defs[req->opcode].plug) {
		blk_start_plug(&state->plug);
		state->plug_started = true;
	}

	if (io_op_defs[req->opcode].needs_file) {
		bool fixed = req->flags & REQ_F_FIXED_FILE;

		req->file = io_file_get(state, req, READ_ONCE(sqe->fd), fixed);
		if (unlikely(!req->file))
			ret = -EBADF;
	}

	state->ios_left--;
	return ret;

#define IORING_MAX_RESTRICTIONS	(IORING_RESTRICTION_LAST + \
				 IORING_REGISTER_LAST + IORING_OP_LAST)

#define SQE_VALID_FLAGS	(IOSQE_FIXED_FILE|IOSQE_IO_DRAIN|IOSQE_IO_LINK|	\
				IOSQE_IO_HARDLINK | IOSQE_ASYNC | \
				IOSQE_BUFFER_SELECT)

struct io_uring {
	u32 head ____cacheline_aligned_in_smp;
	u32 tail ____cacheline_aligned_in_smp;
}

struct io_rings {
	/*
	 * Head and tail offsets into the ring; the offsets need to be
	 * masked to get valid indices.
	 *
	 * The kernel controls head of the sq ring and the tail of the cq ring,
	 * and the application controls tail of the sq ring and the head of the
	 * cq ring.
	 */
	struct io_uring		sq, cq;
	/*
	 * Bitmasks to apply to head and tail offsets (constant, equals
	 * ring_entries - 1)
	 */
	u32			sq_ring_mask, cq_ring_mask;
	/* Ring sizes (constant, power of 2) */
	u32			sq_ring_entries, cq_ring_entries;
	/*
	 * Number of invalid entries dropped by the kernel due to
	 * invalid index stored in array
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * After a new SQ head value was read by the application this
	 * counter includes all submissions that were dropped reaching
	 * the new SQ head (and possibly more).
	 */
	u32			sq_dropped;
	/*
	 * Runtime SQ flags
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application.
	 *
	 * The application needs a full memory barrier before checking
	 * for IORING_SQ_NEED_WAKEUP after updating the sq tail.
	 */
	u32			sq_flags;
	/*
	 * Runtime CQ flags
	 *
	 * Written by the application, shouldn't be modified by the
	 * kernel.
	 */
	u32                     cq_flags;
	/*
	 * Number of completion events lost because the queue was full;
	 * this should be avoided by the application by making sure
	 * there are not more requests pending than there is space in
	 * the completion queue.
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * As completion events come in out of order this counter is not
	 * ordered with any other data.
	 */
	u32			cq_overflow;
	/*
	 * Ring buffer of completion events.
	 *
	 * The kernel writes completion events fresh every time they are
	 * produced, so the application is allowed to modify pending
	 * entries.
	 */
	struct io_uring_cqe	cqes[] ____cacheline_aligned_in_smp;
}

struct io_mapped_ubuf {
	u64		ubuf;
	u64		ubuf_end;
	unsigned int	nr_bvecs;
	unsigned long	acct_pages;
	struct bio_vec	bvec[];
}

struct io_ring_ctx

struct io_overflow_cqe {
	struct io_uring_cqe cqe;
	struct list_head list;
}

struct io_fixed_file {
	/* file * with additional FFS_* flags */
	unsigned long file_ptr;
}

struct io_rsrc_put {
	struct list_head list;
	u64 tag;
	union {
		void *rsrc;
		struct file *file;
		struct io_mapped_ubuf *buf;
	};
}


/* should only be called by SQPOLL task */
static void io_uring_cancel_sqpoll(struct io_sq_data *sqd)
{
	struct io_uring_task *tctx = current->io_uring;
	struct io_ring_ctx *ctx;
	s64 inflight;
	DEFINE_WAIT(wait);

	if (!current->io_uring)
		return;
	WARN_ON_ONCE(!sqd || sqd->thread != current);

	atomic_inc(&tctx->in_idle);
	do {
		/* read completions before cancelations */
		inflight = tctx_inflight(tctx, false);
		if (!inflight)
			break;
		list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
			io_uring_try_cancel_requests(ctx, current, NULL);

		prepare_to_wait(&tctx->wait, &wait, TASK_UNINTERRUPTIBLE);
		/*
		 * If we've seen completions, retry without waiting. This
		 * avoids a race where a completion comes in before we did
		 * prepare_to_wait().
		 */
		if (inflight == tctx_inflight(tctx, false))
			schedule();
		finish_wait(&tctx->wait, &wait);
	} while (1);
	atomic_dec(&tctx->in_idle);

io_uring: truncate lengths larger than MAX_RW_COUNT on provide buffers

Read and write operations are capped to MAX_RW_COUNT. Some read ops rely on
that limit, and that is not guaranteed by the IORING_OP_PROVIDE_BUFFERS.

Truncate those lengths when doing io_add_buffers, so buffer addresses still
use the uncapped length.

Also, take the chance and change struct io_buffer len member to __u32, so
it matches struct io_provide_buffer len member.

This fixes CVE-2021-3491, also reported as ZDI-CAN-13546.

Fixes: ddf0322db79c ("io_uring: add IORING_OP_PROVIDE_BUFFERS")
Reported-by: Billy Jheng Bing-Jhong (@st424204)
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

struct io_uring {
	u32 head ____cacheline_aligned_in_smp;
	u32 tail ____cacheline_aligned_in_smp;
}

struct io_rings {
	/*
	 * Head and tail offsets into the ring; the offsets need to be
	 * masked to get valid indices.
	 *
	 * The kernel controls head of the sq ring and the tail of the cq ring,
	 * and the application controls tail of the sq ring and the head of the
	 * cq ring.
	 */
	struct io_uring		sq, cq;
	/*
	 * Bitmasks to apply to head and tail offsets (constant, equals
	 * ring_entries - 1)
	 */
	u32			sq_ring_mask, cq_ring_mask;
	/* Ring sizes (constant, power of 2) */
	u32			sq_ring_entries, cq_ring_entries;
	/*
	 * Number of invalid entries dropped by the kernel due to
	 * invalid index stored in array
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * After a new SQ head value was read by the application this
	 * counter includes all submissions that were dropped reaching
	 * the new SQ head (and possibly more).
	 */
	u32			sq_dropped;
	/*
	 * Runtime SQ flags
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application.
	 *
	 * The application needs a full memory barrier before checking
	 * for IORING_SQ_NEED_WAKEUP after updating the sq tail.
	 */
	u32			sq_flags;
	/*
	 * Runtime CQ flags
	 *
	 * Written by the application, shouldn't be modified by the
	 * kernel.
	 */
	u32                     cq_flags;
	/*
	 * Number of completion events lost because the queue was full;
	 * this should be avoided by the application by making sure
	 * there are not more requests pending than there is space in
	 * the completion queue.
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * As completion events come in out of order this counter is not
	 * ordered with any other data.
	 */
	u32			cq_overflow;
	/*
	 * Ring buffer of completion events.
	 *
	 * The kernel writes completion events fresh every time they are
	 * produced, so the application is allowed to modify pending
	 * entries.
	 */
	struct io_uring_cqe	cqes[] ____cacheline_aligned_in_smp;
}

struct io_mapped_ubuf {
	u64		ubuf;
	u64		ubuf_end;
	unsigned int	nr_bvecs;
	unsigned long	acct_pages;
	struct bio_vec	bvec[];
}

struct io_ring_ctx

struct io_overflow_cqe {
	struct io_uring_cqe cqe;
	struct list_head list;
}

struct io_fixed_file {
	/* file * with additional FFS_* flags */
	unsigned long file_ptr;
}

struct io_rsrc_put {
	struct list_head list;
	u64 tag;
	union {
		void *rsrc;
		struct file *file;
		struct io_mapped_ubuf *buf;
	};
}

struct io_file_table {
	/* two level table */
	struct io_fixed_file **files;
}

struct io_rsrc_node {
	struct percpu_ref		refs;
	struct list_head		node;
	struct list_head		rsrc_list;
	struct io_rsrc_data		*rsrc_data;
	struct llist_node		llist;
	bool				done;
}


static void io_free_req_deferred(struct io_kiocb *req)
{
	req->task_work.func = io_put_req_deferred_cb;
	if (unlikely(io_req_task_work_add(req)))
		io_req_task_work_add_fallback(req, io_put_req_deferred_cb);
}


static bool io_rw_should_reissue(struct io_kiocb *req)
{
	umode_t mode = file_inode(req->file)->i_mode;
	struct io_ring_ctx *ctx = req->ctx;

	if (!S_ISBLK(mode) && !S_ISREG(mode))
		return false;
	if ((req->flags & REQ_F_NOWAIT) || (io_wq_current_is_worker() &&
	    !(ctx->flags & IORING_SETUP_IOPOLL)))
		return false;
	/*
	 * If ref is dying, we might be running poll reap from the exit work.
	 * Don't attempt to reissue from that path, just let it fail with
	 * -EAGAIN.
	 */
	if (percpu_ref_is_dying(&ctx->refs))
		return false;
	return true;
}

struct io_uring {
	u32 head ____cacheline_aligned_in_smp;
	u32 tail ____cacheline_aligned_in_smp;
}

struct io_rings {
	/*
	 * Head and tail offsets into the ring; the offsets need to be
	 * masked to get valid indices.
	 *
	 * The kernel controls head of the sq ring and the tail of the cq ring,
	 * and the application controls tail of the sq ring and the head of the
	 * cq ring.
	 */
	struct io_uring		sq, cq;
	/*
	 * Bitmasks to apply to head and tail offsets (constant, equals
	 * ring_entries - 1)
	 */
	u32			sq_ring_mask, cq_ring_mask;
	/* Ring sizes (constant, power of 2) */
	u32			sq_ring_entries, cq_ring_entries;
	/*
	 * Number of invalid entries dropped by the kernel due to
	 * invalid index stored in array
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * After a new SQ head value was read by the application this
	 * counter includes all submissions that were dropped reaching
	 * the new SQ head (and possibly more).
	 */
	u32			sq_dropped;
	/*
	 * Runtime SQ flags
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application.
	 *
	 * The application needs a full memory barrier before checking
	 * for IORING_SQ_NEED_WAKEUP after updating the sq tail.
	 */
	u32			sq_flags;
	/*
	 * Runtime CQ flags
	 *
	 * Written by the application, shouldn't be modified by the
	 * kernel.
	 */
	u32			cq_flags;
	/*
	 * Number of completion events lost because the queue was full;
	 * this should be avoided by the application by making sure
	 * there are not more requests pending than there is space in
	 * the completion queue.
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * As completion events come in out of order this counter is not
	 * ordered with any other data.
	 */
	u32			cq_overflow;
	/*
	 * Ring buffer of completion events.
	 *
	 * The kernel writes completion events fresh every time they are
	 * produced, so the application is allowed to modify pending
	 * entries.
	 */
	struct io_uring_cqe	cqes[] ____cacheline_aligned_in_smp;
}

struct io_mapped_ubuf {
	u64		ubuf;
	u64		ubuf_end;
	unsigned int	nr_bvecs;
	unsigned long	acct_pages;
	struct bio_vec	bvec[];
}

struct io_ring_ctx

struct io_overflow_cqe {
	struct io_uring_cqe cqe;
	struct list_head list;
}

struct io_fixed_file {
	/* file * with additional FFS_* flags */
	unsigned long file_ptr;
}

struct io_rsrc_put {
	struct list_head list;
	u64 tag;
	union {
		void *rsrc;
		struct file *file;
		struct io_mapped_ubuf *buf;
	};
}

struct io_file_table {
	/* two level table */
	struct io_fixed_file **files;
}

struct io_rsrc_node {
	struct percpu_ref		refs;
	struct list_head		node;
	struct list_head		rsrc_list;
	struct io_rsrc_data		*rsrc_data;
	struct llist_node		llist;
	bool				done;
}


static void io_free_file_tables(struct io_file_table *table, unsigned nr_files)
{
	unsigned i, nr_tables = DIV_ROUND_UP(nr_files, IORING_MAX_FILES_TABLE);

	for (i = 0; i < nr_tables; i++)
		kfree(table->files[i]);
	kfree(table->files);
	table->files = NULL;

#define IORING_MAX_FILES_TABLE	(1U << IORING_FILE_TABLE_SHIFT)

#define IORING_FILE_TABLE_MASK	(IORING_MAX_FILES_TABLE - 1)

#define IORING_MAX_FIXED_FILES	(64 * IORING_MAX_FILES_TABLE)

struct io_uring {
	u32 head ____cacheline_aligned_in_smp;
	u32 tail ____cacheline_aligned_in_smp;
}

struct io_rings {
	/*
	 * Head and tail offsets into the ring; the offsets need to be
	 * masked to get valid indices.
	 *
	 * The kernel controls head of the sq ring and the tail of the cq ring,
	 * and the application controls tail of the sq ring and the head of the
	 * cq ring.
	 */
	struct io_uring		sq, cq;
	/*
	 * Bitmasks to apply to head and tail offsets (constant, equals
	 * ring_entries - 1)
	 */
	u32			sq_ring_mask, cq_ring_mask;
	/* Ring sizes (constant, power of 2) */
	u32			sq_ring_entries, cq_ring_entries;
	/*
	 * Number of invalid entries dropped by the kernel due to
	 * invalid index stored in array
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * After a new SQ head value was read by the application this
	 * counter includes all submissions that were dropped reaching
	 * the new SQ head (and possibly more).
	 */
	u32			sq_dropped;
	/*
	 * Runtime SQ flags
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application.
	 *
	 * The application needs a full memory barrier before checking
	 * for IORING_SQ_NEED_WAKEUP after updating the sq tail.
	 */
	u32			sq_flags;
	/*
	 * Runtime CQ flags
	 *
	 * Written by the application, shouldn't be modified by the
	 * kernel.
	 */
	u32                     cq_flags;
	/*
	 * Number of completion events lost because the queue was full;
	 * this should be avoided by the application by making sure
	 * there are not more requests pending than there is space in
	 * the completion queue.
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * As completion events come in out of order this counter is not
	 * ordered with any other data.
	 */
	u32			cq_overflow;
	/*
	 * Ring buffer of completion events.
	 *
	 * The kernel writes completion events fresh every time they are
	 * produced, so the application is allowed to modify pending
	 * entries.
	 */
	struct io_uring_cqe	cqes[] ____cacheline_aligned_in_smp;
}

struct io_mapped_ubuf {
	u64		ubuf;
	u64		ubuf_end;
	unsigned int	nr_bvecs;
	unsigned long	acct_pages;
	struct bio_vec	bvec[];
}

struct io_ring_ctx

struct io_overflow_cqe {
	struct io_uring_cqe cqe;
	struct list_head list;
}

struct io_fixed_file {
	/* file * with additional FFS_* flags */
	unsigned long file_ptr;
}

struct io_rsrc_put {
	struct list_head list;
	u64 tag;
	union {
		void *rsrc;
		struct file *file;
		struct io_mapped_ubuf *buf;
	};
}

struct io_file_table {
	/* two level table */
	struct io_fixed_file **files;
}


 */
static inline int io_uring_add_task_file(struct io_ring_ctx *ctx)
{
	struct io_uring_task *tctx = current->io_uring;

	if (likely(tctx && tctx->last == ctx))
		return 0;
	return __io_uring_add_task_file(ctx);


static int io_send(struct io_kiocb *req, unsigned int issue_flags)
{
	struct io_sr_msg *sr = &req->sr_msg;
	struct msghdr msg;
	struct iovec iov;
	struct socket *sock;
	unsigned flags;
	int min_ret = 0;
	int ret;

	sock = sock_from_file(req->file);
	if (unlikely(!sock))
		return -ENOTSOCK;

	ret = import_single_range(WRITE, sr->buf, sr->len, &iov, &msg.msg_iter);
	if (unlikely(ret))
		return ret;

	msg.msg_name = NULL;
	msg.msg_control = NULL;
	msg.msg_controllen = 0;
	msg.msg_namelen = 0;

	flags = req->sr_msg.msg_flags;
	if (issue_flags & IO_URING_F_NONBLOCK)
		flags |= MSG_DONTWAIT;
	if (flags & MSG_WAITALL)
		min_ret = iov_iter_count(&msg.msg_iter);

	msg.msg_flags = flags;
	ret = sock_sendmsg(sock, &msg);
	if ((issue_flags & IO_URING_F_NONBLOCK) && ret == -EAGAIN)
		return -EAGAIN;
	if (ret == -ERESTARTSYS)
		ret = -EINTR;

	if (ret < min_ret)
		req_set_fail_links(req);
	__io_req_complete(req, issue_flags, ret, 0);
	return 0;
}

struct io_uring {
	u32 head ____cacheline_aligned_in_smp;
	u32 tail ____cacheline_aligned_in_smp;
}

struct io_rings {
	/*
	 * Head and tail offsets into the ring; the offsets need to be
	 * masked to get valid indices.
	 *
	 * The kernel controls head of the sq ring and the tail of the cq ring,
	 * and the application controls tail of the sq ring and the head of the
	 * cq ring.
	 */
	struct io_uring		sq, cq;
	/*
	 * Bitmasks to apply to head and tail offsets (constant, equals
	 * ring_entries - 1)
	 */
	u32			sq_ring_mask, cq_ring_mask;
	/* Ring sizes (constant, power of 2) */
	u32			sq_ring_entries, cq_ring_entries;
	/*
	 * Number of invalid entries dropped by the kernel due to
	 * invalid index stored in array
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * After a new SQ head value was read by the application this
	 * counter includes all submissions that were dropped reaching
	 * the new SQ head (and possibly more).
	 */
	u32			sq_dropped;
	/*
	 * Runtime SQ flags
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application.
	 *
	 * The application needs a full memory barrier before checking
	 * for IORING_SQ_NEED_WAKEUP after updating the sq tail.
	 */
	u32			sq_flags;
	/*
	 * Runtime CQ flags
	 *
	 * Written by the application, shouldn't be modified by the
	 * kernel.
	 */
	u32                     cq_flags;
	/*
	 * Number of completion events lost because the queue was full;
	 * this should be avoided by the application by making sure
	 * there are not more requests pending than there is space in
	 * the completion queue.
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * As completion events come in out of order this counter is not
	 * ordered with any other data.
	 */
	u32			cq_overflow;
	/*
	 * Ring buffer of completion events.
	 *
	 * The kernel writes completion events fresh every time they are
	 * produced, so the application is allowed to modify pending
	 * entries.
	 */
	struct io_uring_cqe	cqes[] ____cacheline_aligned_in_smp;
}

enum io_uring_cmd_flags {
	IO_URING_F_NONBLOCK		= 1,
	IO_URING_F_COMPLETE_DEFER	= 2,
}

struct io_mapped_ubuf {
	u64		ubuf;
	u64		ubuf_end;
	unsigned int	nr_bvecs;
	unsigned long	acct_pages;
	struct bio_vec	bvec[];
}

struct io_ring_ctx

struct io_overflow_cqe {
	struct io_uring_cqe cqe;
	struct list_head list;
}

struct io_fixed_file {
	/* file * with additional FFS_* flags */
	unsigned long file_ptr;
}

struct io_rsrc_put {
	struct list_head list;
	u64 tag;
	union {
		void *rsrc;
		struct file *file;
		struct io_mapped_ubuf *buf;
	};
}

struct io_file_table {
	/* two level table */
	struct io_fixed_file **files;
}


static int __io_splice_prep(struct io_kiocb *req,
			    const struct io_uring_sqe *sqe)
{
	struct io_splice* sp = &req->splice;
	unsigned int valid_flags = SPLICE_F_FD_IN_FIXED | SPLICE_F_ALL;

	if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
		return -EINVAL;

	sp->file_in = NULL;
	sp->len = READ_ONCE(sqe->len);
	sp->flags = READ_ONCE(sqe->splice_flags);

	if (unlikely(sp->flags & ~valid_flags))
		return -EINVAL;

	sp->file_in = io_file_get(NULL, req, READ_ONCE(sqe->splice_fd_in),
				  (sp->flags & SPLICE_F_FD_IN_FIXED));
	if (!sp->file_in)
		return -EBADF;
	req->flags |= REQ_F_NEED_CLEANUP;
	return 0;
}

#define IO_REQ_CLEAN_FLAGS (REQ_F_BUFFER_SELECTED | REQ_F_NEED_CLEANUP | \
				REQ_F_POLLED | REQ_F_INFLIGHT | REQ_F_CREDS)

struct io_uring {
	u32 head ____cacheline_aligned_in_smp;
	u32 tail ____cacheline_aligned_in_smp;
}

struct io_rings {
	/*
	 * Head and tail offsets into the ring; the offsets need to be
	 * masked to get valid indices.
	 *
	 * The kernel controls head of the sq ring and the tail of the cq ring,
	 * and the application controls tail of the sq ring and the head of the
	 * cq ring.
	 */
	struct io_uring		sq, cq;
	/*
	 * Bitmasks to apply to head and tail offsets (constant, equals
	 * ring_entries - 1)
	 */
	u32			sq_ring_mask, cq_ring_mask;
	/* Ring sizes (constant, power of 2) */
	u32			sq_ring_entries, cq_ring_entries;
	/*
	 * Number of invalid entries dropped by the kernel due to
	 * invalid index stored in array
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * After a new SQ head value was read by the application this
	 * counter includes all submissions that were dropped reaching
	 * the new SQ head (and possibly more).
	 */
	u32			sq_dropped;
	/*
	 * Runtime SQ flags
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application.
	 *
	 * The application needs a full memory barrier before checking
	 * for IORING_SQ_NEED_WAKEUP after updating the sq tail.
	 */
	u32			sq_flags;
	/*
	 * Runtime CQ flags
	 *
	 * Written by the application, shouldn't be modified by the
	 * kernel.
	 */
	u32			cq_flags;
	/*
	 * Number of completion events lost because the queue was full;
	 * this should be avoided by the application by making sure
	 * there are not more requests pending than there is space in
	 * the completion queue.
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * As completion events come in out of order this counter is not
	 * ordered with any other data.
	 */
	u32			cq_overflow;
	/*
	 * Ring buffer of completion events.
	 *
	 * The kernel writes completion events fresh every time they are
	 * produced, so the application is allowed to modify pending
	 * entries.
	 */
	struct io_uring_cqe	cqes[] ____cacheline_aligned_in_smp;
}

struct io_mapped_ubuf {
	u64		ubuf;
	u64		ubuf_end;
	unsigned int	nr_bvecs;
	unsigned long	acct_pages;
	struct bio_vec	bvec[];
}

struct io_ring_ctx

struct io_overflow_cqe {
	struct io_uring_cqe cqe;
	struct list_head list;
}

struct io_fixed_file {
	/* file * with additional FFS_* flags */
	unsigned long file_ptr;
}

struct io_rsrc_put {
	struct list_head list;
	u64 tag;
	union {
		void *rsrc;
		struct file *file;
		struct io_mapped_ubuf *buf;
	};
}

struct io_file_table {
	/* two level table */
	struct io_fixed_file **files;
}


static struct io_wq *io_init_wq_offload(struct io_ring_ctx *ctx,
					struct task_struct *task)
{
	struct io_wq_hash *hash;
	struct io_wq_data data;
	unsigned int concurrency;

	hash = ctx->hash_map;
	if (!hash) {
		hash = kzalloc(sizeof(*hash), GFP_KERNEL);
		if (!hash)
			return ERR_PTR(-ENOMEM);
		refcount_set(&hash->refs, 1);
		init_waitqueue_head(&hash->wait);
		ctx->hash_map = hash;
	}

	data.hash = hash;
	data.task = task;
	data.free_work = io_free_work;
	data.do_work = io_wq_submit_work;

	/* Do QD, or 4 * CPUS, whatever is smallest */
	concurrency = min(ctx->sq_entries, 4 * num_online_cpus());

	return io_wq_create(concurrency, &data);


static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
	struct io_ring_ctx *ctx = req->ctx;
	struct kiocb *kiocb = &req->rw.kiocb;
	struct file *file = req->file;
	unsigned ioprio;
	int ret;

	if (!(req->flags & REQ_F_ISREG) && S_ISREG(file_inode(file)->i_mode))
		req->flags |= REQ_F_ISREG;

	kiocb->ki_pos = READ_ONCE(sqe->off);
	if (kiocb->ki_pos == -1 && !(file->f_mode & FMODE_STREAM)) {
		req->flags |= REQ_F_CUR_POS;
		kiocb->ki_pos = file->f_pos;
	}
	kiocb->ki_hint = ki_hint_validate(file_write_hint(kiocb->ki_filp));
	kiocb->ki_flags = iocb_flags(kiocb->ki_filp);
	ret = kiocb_set_rw_flags(kiocb, READ_ONCE(sqe->rw_flags));
	if (unlikely(ret))
		return ret;

	/* don't allow async punt for O_NONBLOCK or RWF_NOWAIT */
	if ((kiocb->ki_flags & IOCB_NOWAIT) || (file->f_flags & O_NONBLOCK))
		req->flags |= REQ_F_NOWAIT;

	ioprio = READ_ONCE(sqe->ioprio);
	if (ioprio) {
		ret = ioprio_check_cap(ioprio);
		if (ret)
			return ret;

		kiocb->ki_ioprio = ioprio;
	} else
		kiocb->ki_ioprio = get_current_ioprio();

	if (ctx->flags & IORING_SETUP_IOPOLL) {
		if (!(kiocb->ki_flags & IOCB_DIRECT) ||
		    !kiocb->ki_filp->f_op->iopoll)
			return -EOPNOTSUPP;

		kiocb->ki_flags |= IOCB_HIPRI;
		kiocb->ki_complete = io_complete_rw_iopoll;
		req->iopoll_completed = 0;
	} else {
		if (kiocb->ki_flags & IOCB_HIPRI)
			return -EINVAL;
		kiocb->ki_complete = io_complete_rw;
	}

	if (req->opcode == IORING_OP_READ_FIXED ||
	    req->opcode == IORING_OP_WRITE_FIXED) {
		req->imu = NULL;
		io_req_set_rsrc_node(req);
	}

	req->rw.addr = READ_ONCE(sqe->addr);
	req->rw.len = READ_ONCE(sqe->len);
	req->buf_index = READ_ONCE(sqe->buf_index);
	return 0;
}


				      wait_queue_func_t wake_func)
	__acquires(&ctx->completion_lock)
{
	struct io_ring_ctx *ctx = req->ctx;
	bool cancel = false;

	INIT_HLIST_NODE(&req->hash_node);
	io_init_poll_iocb(poll, mask, wake_func);
	poll->file = req->file;
	poll->wait.private = req;

	ipt->pt._key = mask;
	ipt->req = req;
	ipt->error = -EINVAL;

	mask = vfs_poll(req->file, &ipt->pt) & poll->events;

	spin_lock_irq(&ctx->completion_lock);
	if (likely(poll->head)) {
		spin_lock(&poll->head->lock);
		if (unlikely(list_empty(&poll->wait.entry))) {
			if (ipt->error)
				cancel = true;
			ipt->error = 0;
			mask = 0;
		}
		if ((mask && (poll->events & EPOLLONESHOT)) || ipt->error)
			list_del_init(&poll->wait.entry);
		else if (cancel)
			WRITE_ONCE(poll->canceled, true);
		else if (!poll->done) /* actually waiting for an event */
			io_poll_req_insert(req);
		spin_unlock(&poll->head->lock);
	}

	return mask;


					   __u64 user_data)
	__must_hold(&ctx->completion_lock)
{
	struct io_timeout_data *io;
	struct io_kiocb *req;
	bool found = false;

	list_for_each_entry(req, &ctx->timeout_list, timeout.list) {
		found = user_data == req->user_data;
		if (found)
			break;
	}
	if (!found)
		return ERR_PTR(-ENOENT);

	io = req->async_data;
	if (hrtimer_try_to_cancel(&io->timer) == -1)
		return ERR_PTR(-EALREADY);
	list_del_init(&req->timeout.list);
	return req;


#ifdef CONFIG_PROC_FS
static int io_uring_show_cred(struct seq_file *m, unsigned int id,
		const struct cred *cred)
{
	struct user_namespace *uns = seq_user_ns(m);
	struct group_info *gi;
	kernel_cap_t cap;
	unsigned __capi;
	int g;

	seq_printf(m, "%5d\n", id);
	seq_put_decimal_ull(m, "\tUid:\t", from_kuid_munged(uns, cred->uid));
	seq_put_decimal_ull(m, "\t\t", from_kuid_munged(uns, cred->euid));
	seq_put_decimal_ull(m, "\t\t", from_kuid_munged(uns, cred->suid));
	seq_put_decimal_ull(m, "\t\t", from_kuid_munged(uns, cred->fsuid));
	seq_put_decimal_ull(m, "\n\tGid:\t", from_kgid_munged(uns, cred->gid));
	seq_put_decimal_ull(m, "\t\t", from_kgid_munged(uns, cred->egid));
	seq_put_decimal_ull(m, "\t\t", from_kgid_munged(uns, cred->sgid));
	seq_put_decimal_ull(m, "\t\t", from_kgid_munged(uns, cred->fsgid));
	seq_puts(m, "\n\tGroups:\t");
	gi = cred->group_info;
	for (g = 0; g < gi->ngroups; g++) {
		seq_put_decimal_ull(m, g ? " " : "",
					from_kgid_munged(uns, gi->gid[g]));
	}
	seq_puts(m, "\n\tCapEff:\t");
	cap = cred->cap_effective;
	CAP_FOR_EACH_U32(__capi)
		seq_put_hex_ll(m, NULL, cap.cap[CAP_LAST_U32 - __capi], 8);
	seq_putc(m, '\n');
	return 0;


static inline struct file *io_file_from_index(struct io_ring_ctx *ctx,
					      int index)
{
	struct io_fixed_file *slot = io_fixed_file_slot(&ctx->file_table, index);

	return (struct file *) (slot->file_ptr & FFS_MASK);

struct io_uring {
	u32 head ____cacheline_aligned_in_smp;
	u32 tail ____cacheline_aligned_in_smp;
}

struct io_rings {
	/*
	 * Head and tail offsets into the ring; the offsets need to be
	 * masked to get valid indices.
	 *
	 * The kernel controls head of the sq ring and the tail of the cq ring,
	 * and the application controls tail of the sq ring and the head of the
	 * cq ring.
	 */
	struct io_uring		sq, cq;
	/*
	 * Bitmasks to apply to head and tail offsets (constant, equals
	 * ring_entries - 1)
	 */
	u32			sq_ring_mask, cq_ring_mask;
	/* Ring sizes (constant, power of 2) */
	u32			sq_ring_entries, cq_ring_entries;
	/*
	 * Number of invalid entries dropped by the kernel due to
	 * invalid index stored in array
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * After a new SQ head value was read by the application this
	 * counter includes all submissions that were dropped reaching
	 * the new SQ head (and possibly more).
	 */
	u32			sq_dropped;
	/*
	 * Runtime SQ flags
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application.
	 *
	 * The application needs a full memory barrier before checking
	 * for IORING_SQ_NEED_WAKEUP after updating the sq tail.
	 */
	u32			sq_flags;
	/*
	 * Runtime CQ flags
	 *
	 * Written by the application, shouldn't be modified by the
	 * kernel.
	 */
	u32			cq_flags;
	/*
	 * Number of completion events lost because the queue was full;
	 * this should be avoided by the application by making sure
	 * there are not more requests pending than there is space in
	 * the completion queue.
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * As completion events come in out of order this counter is not
	 * ordered with any other data.
	 */
	u32			cq_overflow;
	/*
	 * Ring buffer of completion events.
	 *
	 * The kernel writes completion events fresh every time they are
	 * produced, so the application is allowed to modify pending
	 * entries.
	 */
	struct io_uring_cqe	cqes[] ____cacheline_aligned_in_smp;
}

enum io_uring_cmd_flags {
	IO_URING_F_COMPLETE_DEFER	= 1,
	IO_URING_F_UNLOCKED		= 2,
	/* int's last bit, sign checks are usually faster than a bit test */
	IO_URING_F_NONBLOCK		= INT_MIN,
}

struct io_mapped_ubuf {
	u64		ubuf;
	u64		ubuf_end;
	unsigned int	nr_bvecs;
	unsigned long	acct_pages;
	struct bio_vec	bvec[];
}

struct io_ring_ctx

struct io_overflow_cqe {
	struct io_uring_cqe cqe;
	struct list_head list;
}

struct io_fixed_file {
	/* file * with additional FFS_* flags */
	unsigned long file_ptr;
}

struct io_rsrc_put {
	struct list_head list;
	u64 tag;
	union {
		void *rsrc;
		struct file *file;
		struct io_mapped_ubuf *buf;
	};
}

struct io_file_table {
	struct io_fixed_file *files;
}


static bool io_match_task(struct io_kiocb *head,
			  struct task_struct *task,
			  struct files_struct *files)
{
	struct io_kiocb *req;

	if (task && head->task != task)
		return false;
	if (!files)
		return true;

	io_for_each_link(req, head) {
		if (req->flags & REQ_F_INFLIGHT)
			return true;
	}
	return false;
}


static int __io_import_fixed(struct io_kiocb *req, int rw, struct iov_iter *iter,
			     struct io_mapped_ubuf *imu)
{
	size_t len = req->rw.len;
	u64 buf_end, buf_addr = req->rw.addr;
	size_t offset;

	if (unlikely(check_add_overflow(buf_addr, (u64)len, &buf_end)))
		return -EFAULT;
	/* not inside the mapped region */
	if (unlikely(buf_addr < imu->ubuf || buf_end > imu->ubuf_end))
		return -EFAULT;

	/*
	 * May not be a start of buffer, set size appropriately
	 * and advance us to the beginning.
	 */
	offset = buf_addr - imu->ubuf;
	iov_iter_bvec(iter, rw, imu->bvec, imu->nr_bvecs, offset + len);

	if (offset) {
		/*
		 * Don't use iov_iter_advance() here, as it's really slow for
		 * using the latter parts of a big fixed buffer - it iterates
		 * over each segment manually. We can cheat a bit here, because
		 * we know that:
		 *
		 * 1) it's a BVEC iter, we set it up
		 * 2) all bvecs are PAGE_SIZE in size, except potentially the
		 *    first and last bvec
		 *
		 * So just find our index, and adjust the iterator afterwards.
		 * If the offset is within the first bvec (or the whole first
		 * bvec, just use iov_iter_advance(). This makes it easier
		 * since we can just skip the first segment, which may not
		 * be PAGE_SIZE aligned.
		 */
		const struct bio_vec *bvec = imu->bvec;

		if (offset <= bvec->bv_len) {
			iov_iter_advance(iter, offset);
		} else {
			unsigned long seg_skip;

			/* skip first vec */
			offset -= bvec->bv_len;
			seg_skip = 1 + (offset >> PAGE_SHIFT);

			iter->bvec = bvec + seg_skip;
			iter->nr_segs -= seg_skip;
			iter->count -= bvec->bv_len + offset;
			iter->iov_offset = offset & ~PAGE_MASK;
		}
	}

	return 0;
}

#define IO_RSRC_TAG_TABLE_SHIFT	(PAGE_SHIFT - 3)

struct io_uring {
	u32 head ____cacheline_aligned_in_smp;
	u32 tail ____cacheline_aligned_in_smp;
}

struct io_rings {
	/*
	 * Head and tail offsets into the ring; the offsets need to be
	 * masked to get valid indices.
	 *
	 * The kernel controls head of the sq ring and the tail of the cq ring,
	 * and the application controls tail of the sq ring and the head of the
	 * cq ring.
	 */
	struct io_uring		sq, cq;
	/*
	 * Bitmasks to apply to head and tail offsets (constant, equals
	 * ring_entries - 1)
	 */
	u32			sq_ring_mask, cq_ring_mask;
	/* Ring sizes (constant, power of 2) */
	u32			sq_ring_entries, cq_ring_entries;
	/*
	 * Number of invalid entries dropped by the kernel due to
	 * invalid index stored in array
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * After a new SQ head value was read by the application this
	 * counter includes all submissions that were dropped reaching
	 * the new SQ head (and possibly more).
	 */
	u32			sq_dropped;
	/*
	 * Runtime SQ flags
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application.
	 *
	 * The application needs a full memory barrier before checking
	 * for IORING_SQ_NEED_WAKEUP after updating the sq tail.
	 */
	u32			sq_flags;
	/*
	 * Runtime CQ flags
	 *
	 * Written by the application, shouldn't be modified by the
	 * kernel.
	 */
	u32			cq_flags;
	/*
	 * Number of completion events lost because the queue was full;
	 * this should be avoided by the application by making sure
	 * there are not more requests pending than there is space in
	 * the completion queue.
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * As completion events come in out of order this counter is not
	 * ordered with any other data.
	 */
	u32			cq_overflow;
	/*
	 * Ring buffer of completion events.
	 *
	 * The kernel writes completion events fresh every time they are
	 * produced, so the application is allowed to modify pending
	 * entries.
	 */
	struct io_uring_cqe	cqes[] ____cacheline_aligned_in_smp;
}

enum io_uring_cmd_flags {
	IO_URING_F_COMPLETE_DEFER	= 1,
	IO_URING_F_UNLOCKED		= 2,
	/* int's last bit, sign checks are usually faster than a bit test */
	IO_URING_F_NONBLOCK		= INT_MIN,
}

struct io_mapped_ubuf {
	u64		ubuf;
	u64		ubuf_end;
	unsigned int	nr_bvecs;
	unsigned long	acct_pages;
	struct bio_vec	bvec[];
}

struct io_ring_ctx

struct io_overflow_cqe {
	struct io_uring_cqe cqe;
	struct list_head list;
}

struct io_fixed_file {
	/* file * with additional FFS_* flags */
	unsigned long file_ptr;
}


static bool __io_file_supports_async(struct file *file, int rw)
{
	umode_t mode = file_inode(file)->i_mode;

	if (S_ISBLK(mode)) {
		if (IS_ENABLED(CONFIG_BLOCK) &&
		    io_bdev_nowait(I_BDEV(file->f_mapping->host)))
			return true;
		return false;
	}
	if (S_ISCHR(mode) || S_ISSOCK(mode))
		return true;
	if (S_ISREG(mode)) {
		if (IS_ENABLED(CONFIG_BLOCK) &&
		    io_bdev_nowait(file->f_inode->i_sb->s_bdev) &&
		    file->f_op != &io_uring_fops)
			return true;
		return false;
	}

	/* any ->read/write should understand O_NONBLOCK */
	if (file->f_flags & O_NONBLOCK)
		return true;

	if (!(file->f_mode & FMODE_NOWAIT))
		return false;

	if (rw == READ)
		return file->f_op->read_iter != NULL;

	return file->f_op->write_iter != NULL;
}


static bool req_need_defer(struct io_kiocb *req, u32 seq)
{
	if (unlikely(req->flags & REQ_F_IO_DRAIN)) {
		struct io_ring_ctx *ctx = req->ctx;

		return seq + ctx->cq_extra != ctx->cached_cq_tail
				+ READ_ONCE(ctx->cached_cq_overflow);
	}

	return false;
}


 */
static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
			  const sigset_t __user *sig, size_t sigsz,
			  struct __kernel_timespec __user *uts)
{
	struct io_wait_queue iowq = {
		.wq = {
			.private	= current,
			.func		= io_wake_function,
			.entry		= LIST_HEAD_INIT(iowq.wq.entry),
		},
		.ctx		= ctx,
		.to_wait	= min_events,
	};
	struct io_rings *rings = ctx->rings;
	signed long timeout = MAX_SCHEDULE_TIMEOUT;
	int ret;

	do {
		io_cqring_overflow_flush(ctx, false);
		if (io_cqring_events(ctx) >= min_events)
			return 0;
		if (!io_run_task_work())
			break;
	} while (1);

	if (sig) {
#ifdef CONFIG_COMPAT
		if (in_compat_syscall())
			ret = set_compat_user_sigmask((const compat_sigset_t __user *)sig,
						      sigsz);
		else
#endif
			ret = set_user_sigmask(sig, sigsz);

		if (ret)
			return ret;
	}

	if (uts) {
		struct timespec64 ts;

		if (get_timespec64(&ts, uts))
			return -EFAULT;
		timeout = timespec64_to_jiffies(&ts);
	}

	iowq.nr_timeouts = atomic_read(&ctx->cq_timeouts);
	trace_io_uring_cqring_wait(ctx, min_events);
	do {
		/* if we can't even flush overflow, don't wait for more */
		if (!io_cqring_overflow_flush(ctx, false)) {
			ret = -EBUSY;
			break;
		}
		prepare_to_wait_exclusive(&ctx->wait, &iowq.wq,
						TASK_INTERRUPTIBLE);
		ret = io_cqring_wait_schedule(ctx, &iowq, &timeout);
		finish_wait(&ctx->wait, &iowq.wq);
		cond_resched();
	} while (ret > 0);

	restore_saved_sigmask_unless(ret == -EINTR);

	return READ_ONCE(rings->cq.head) == READ_ONCE(rings->cq.tail) ? ret : 0;


static inline void io_put_req(struct io_kiocb *req)
{
	if (req_ref_put_and_test(req))
		io_free_req(req);
}

struct io_uring {
	u32 head ____cacheline_aligned_in_smp;
	u32 tail ____cacheline_aligned_in_smp;
}

struct io_rings {
	/*
	 * Head and tail offsets into the ring; the offsets need to be
	 * masked to get valid indices.
	 *
	 * The kernel controls head of the sq ring and the tail of the cq ring,
	 * and the application controls tail of the sq ring and the head of the
	 * cq ring.
	 */
	struct io_uring		sq, cq;
	/*
	 * Bitmasks to apply to head and tail offsets (constant, equals
	 * ring_entries - 1)
	 */
	u32			sq_ring_mask, cq_ring_mask;
	/* Ring sizes (constant, power of 2) */
	u32			sq_ring_entries, cq_ring_entries;
	/*
	 * Number of invalid entries dropped by the kernel due to
	 * invalid index stored in array
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * After a new SQ head value was read by the application this
	 * counter includes all submissions that were dropped reaching
	 * the new SQ head (and possibly more).
	 */
	u32			sq_dropped;
	/*
	 * Runtime SQ flags
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application.
	 *
	 * The application needs a full memory barrier before checking
	 * for IORING_SQ_NEED_WAKEUP after updating the sq tail.
	 */
	u32			sq_flags;
	/*
	 * Runtime CQ flags
	 *
	 * Written by the application, shouldn't be modified by the
	 * kernel.
	 */
	u32			cq_flags;
	/*
	 * Number of completion events lost because the queue was full;
	 * this should be avoided by the application by making sure
	 * there are not more requests pending than there is space in
	 * the completion queue.
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * As completion events come in out of order this counter is not
	 * ordered with any other data.
	 */
	u32			cq_overflow;
	/*
	 * Ring buffer of completion events.
	 *
	 * The kernel writes completion events fresh every time they are
	 * produced, so the application is allowed to modify pending
	 * entries.
	 */
	struct io_uring_cqe	cqes[] ____cacheline_aligned_in_smp;
}

struct io_mapped_ubuf {
	u64		ubuf;
	u64		ubuf_end;
	unsigned int	nr_bvecs;
	unsigned long	acct_pages;
	struct bio_vec	bvec[];
}

struct io_ring_ctx

struct io_overflow_cqe {
	struct io_uring_cqe cqe;
	struct list_head list;
}

struct io_fixed_file {
	/* file * with additional FFS_* flags */
	unsigned long file_ptr;
}

struct io_rsrc_put {
	struct list_head list;
	u64 tag;
	union {
		void *rsrc;
		struct file *file;
		struct io_mapped_ubuf *buf;
	};
}

struct io_file_table {
	struct io_fixed_file *files;
}

struct io_rsrc_node {
	struct percpu_ref		refs;
	struct list_head		node;
	struct list_head		rsrc_list;
	struct io_rsrc_data		*rsrc_data;
	struct llist_node		llist;
	bool				done;
}


static void io_flush_cached_locked_reqs(struct io_ring_ctx *ctx,
					struct io_comp_state *cs)
{
	spin_lock_irq(&ctx->completion_lock);
	list_splice_init(&cs->locked_free_list, &cs->free_list);
	cs->locked_free_nr = 0;
	spin_unlock_irq(&ctx->completion_lock);
}


static void io_req_task_queue(struct io_kiocb *req)
{
	req->task_work.func = io_req_task_submit;

	if (unlikely(io_req_task_work_add(req)))
		io_req_task_queue_fail(req, -ECANCELED);
}


static int io_register_enable_rings(struct io_ring_ctx *ctx)
{
	if (!(ctx->flags & IORING_SETUP_R_DISABLED))
		return -EBADFD;

	if (ctx->restrictions.registered)
		ctx->restricted = 1;

	ctx->flags &= ~IORING_SETUP_R_DISABLED;
	if (ctx->sq_data && wq_has_sleeper(&ctx->sq_data->wait))
		wake_up(&ctx->sq_data->wait);
	return 0;


static bool io_file_supports_async(struct io_kiocb *req, int rw)
{
	if (rw == READ && (req->flags & REQ_F_ASYNC_READ))
		return true;
	else if (rw == WRITE && (req->flags & REQ_F_ASYNC_WRITE))
		return true;

	return __io_file_supports_async(req->file, rw);
}


static int io_openat2(struct io_kiocb *req, unsigned int issue_flags)
{
	struct open_flags op;
	struct file *file;
	bool nonblock_set;
	bool resolve_nonblock;
	int ret;

	ret = build_open_flags(&req->open.how, &op);
	if (ret)
		goto err;
	nonblock_set = op.open_flag & O_NONBLOCK;
	resolve_nonblock = req->open.how.resolve & RESOLVE_CACHED;
	if (issue_flags & IO_URING_F_NONBLOCK) {
		/*
		 * Don't bother trying for O_TRUNC, O_CREAT, or O_TMPFILE open,
		 * it'll always -EAGAIN
		 */
		if (req->open.how.flags & (O_TRUNC | O_CREAT | O_TMPFILE))
			return -EAGAIN;
		op.lookup_flags |= LOOKUP_CACHED;
		op.open_flag |= O_NONBLOCK;
	}

	ret = __get_unused_fd_flags(req->open.how.flags, req->open.nofile);
	if (ret < 0)
		goto err;

	file = do_filp_open(req->open.dfd, req->open.filename, &op);
	/* only retry if RESOLVE_CACHED wasn't already set by application */
	if ((!resolve_nonblock && (issue_flags & IO_URING_F_NONBLOCK)) &&
	    file == ERR_PTR(-EAGAIN)) {
		/*
		 * We could hang on to this 'fd', but seems like marginal
		 * gain for something that is now known to be a slower path.
		 * So just put it, and we'll get a new one when we retry.
		 */
		put_unused_fd(ret);
		return -EAGAIN;
	}

	if (IS_ERR(file)) {
		put_unused_fd(ret);
		ret = PTR_ERR(file);
	} else {
		if ((issue_flags & IO_URING_F_NONBLOCK) && !nonblock_set)
			file->f_flags &= ~O_NONBLOCK;
		fsnotify_open(file);
		fd_install(ret, file);
	}
err:
	putname(req->open.filename);
	req->flags &= ~REQ_F_NEED_CLEANUP;
	if (ret < 0)
		req_set_fail_links(req);
	__io_req_complete(req, issue_flags, ret, 0);
	return 0;
}


static int io_run_task_work_sig(void)
{
	if (io_run_task_work())
		return 1;
	if (!signal_pending(current))
		return 0;
	if (test_thread_flag(TIF_NOTIFY_SIGNAL))
		return -ERESTARTSYS;
	return -EINTR;

struct io_mapped_ubuf {
	u64		ubuf;
	u64		ubuf_end;
	unsigned int	nr_bvecs;
	unsigned long	acct_pages;
	struct bio_vec	bvec[];
}

struct io_rsrc_put {
	struct list_head list;
	u64 tag;
	union {
		void *rsrc;
		struct file *file;
		struct io_mapped_ubuf *buf;
	};
}

typedef void (rsrc_put_fn)(struct io_ring_ctx *ctx, struct io_rsrc_put *prsrc);

struct io_rsrc_data {
	struct io_ring_ctx		*ctx;

	u64				**tags;
	unsigned int			nr;
	rsrc_put_fn			*do_put;
	atomic_t			refs;
	struct completion		done;
	bool				quiesce;
}

struct io_sq_data {
	refcount_t		refs;
	atomic_t		park_pending;
	struct mutex		lock;

	/* ctx's that are using this sqd */
	struct list_head	ctx_list;

	struct task_struct	*thread;
	struct wait_queue_head	wait;

	unsigned		sq_thread_idle;
	int			sq_cpu;
	pid_t			task_pid;
	pid_t			task_tgid;

	unsigned long		state;
	struct completion	exited;
}

struct io_comp_state {
	struct io_kiocb		*reqs[IO_COMPL_BATCH];
	unsigned int		nr;
	/* inline/task_work completion list, under ->uring_lock */
	struct list_head	free_list;
}

struct io_submit_state {
	struct blk_plug		plug;
	struct io_submit_link	link;

	/*
	 * io_kiocb alloc cache
	 */
	void			*reqs[IO_REQ_CACHE_SIZE];
	unsigned int		free_reqs;

	bool			plug_started;

	/*
	 * Batch completion logic
	 */
	struct io_comp_state	comp;

	/*
	 * File reference cache
	 */
	struct file		*file;
	unsigned int		fd;
	unsigned int		file_refs;
	unsigned int		ios_left;
}


static int io_buffers_map_alloc(struct io_ring_ctx *ctx, unsigned int nr_args)
{
	ctx->user_bufs = kcalloc(nr_args, sizeof(*ctx->user_bufs), GFP_KERNEL);
	return ctx->user_bufs ? 0 : -ENOMEM;


static void io_ring_ctx_free(struct io_ring_ctx *ctx)
{
	io_sq_thread_finish(ctx);

	if (ctx->mm_account) {
		mmdrop(ctx->mm_account);
		ctx->mm_account = NULL;
	}

	mutex_lock(&ctx->uring_lock);
	if (io_wait_rsrc_data(ctx->buf_data))
		__io_sqe_buffers_unregister(ctx);
	if (io_wait_rsrc_data(ctx->file_data))
		__io_sqe_files_unregister(ctx);
	if (ctx->rings)
		__io_cqring_overflow_flush(ctx, true);
	mutex_unlock(&ctx->uring_lock);
	io_eventfd_unregister(ctx);
	io_destroy_buffers(ctx);
	if (ctx->sq_creds)
		put_cred(ctx->sq_creds);

	/* there are no registered resources left, nobody uses it */
	if (ctx->rsrc_node)
		io_rsrc_node_destroy(ctx->rsrc_node);
	if (ctx->rsrc_backup_node)
		io_rsrc_node_destroy(ctx->rsrc_backup_node);
	flush_delayed_work(&ctx->rsrc_put_work);

	WARN_ON_ONCE(!list_empty(&ctx->rsrc_ref_list));
	WARN_ON_ONCE(!llist_empty(&ctx->rsrc_put_llist));

#if defined(CONFIG_UNIX)
	if (ctx->ring_sock) {
		ctx->ring_sock->file = NULL; /* so that iput() is called */
		sock_release(ctx->ring_sock);
	}
#endif

	io_mem_free(ctx->rings);
	io_mem_free(ctx->sq_sqes);

	percpu_ref_exit(&ctx->refs);
	free_uid(ctx->user);
	io_req_caches_free(ctx);
	if (ctx->hash_map)
		io_wq_put_hash(ctx->hash_map);
	kfree(ctx->cancel_hash);
	kfree(ctx->dummy_ubuf);
	kfree(ctx);


static inline bool req_ref_put_and_test(struct io_kiocb *req)
{
	WARN_ON_ONCE(req_ref_zero_or_close_to_overflow(req));
	return atomic_dec_and_test(&req->refs);
}


static int io_provide_buffers_prep(struct io_kiocb *req,
				   const struct io_uring_sqe *sqe)
{
	unsigned long size, tmp_check;
	struct io_provide_buf *p = &req->pbuf;
	u64 tmp;

	if (sqe->ioprio || sqe->rw_flags)
		return -EINVAL;

	tmp = READ_ONCE(sqe->fd);
	if (!tmp || tmp > USHRT_MAX)
		return -E2BIG;
	p->nbufs = tmp;
	p->addr = READ_ONCE(sqe->addr);
	p->len = READ_ONCE(sqe->len);

	if (check_mul_overflow((unsigned long)p->len, (unsigned long)p->nbufs,
				&size))
		return -EOVERFLOW;
	if (check_add_overflow((unsigned long)p->addr, size, &tmp_check))
		return -EOVERFLOW;

	size = (unsigned long)p->len * p->nbufs;
	if (!access_ok(u64_to_user_ptr(p->addr), size))
		return -EFAULT;

	p->bgid = READ_ONCE(sqe->buf_group);
	tmp = READ_ONCE(sqe->off);
	if (tmp > USHRT_MAX)
		return -E2BIG;
	p->bid = tmp;
	return 0;
}


static int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
				   unsigned int nr_args, u64 __user *tags)
{
	struct page *last_hpage = NULL;
	struct io_rsrc_data *data;
	int i, ret;
	struct iovec iov;

	if (ctx->user_bufs)
		return -EBUSY;
	if (!nr_args || nr_args > UIO_MAXIOV)
		return -EINVAL;
	ret = io_rsrc_node_switch_start(ctx);
	if (ret)
		return ret;
	data = io_rsrc_data_alloc(ctx, io_rsrc_buf_put, nr_args);
	if (!data)
		return -ENOMEM;
	ret = io_buffers_map_alloc(ctx, nr_args);
	if (ret) {
		io_rsrc_data_free(data);
		return ret;
	}

	for (i = 0; i < nr_args; i++, ctx->nr_user_bufs++) {
		u64 tag = 0;

		if (tags && copy_from_user(&tag, &tags[i], sizeof(tag))) {
			ret = -EFAULT;
			break;
		}
		ret = io_copy_iov(ctx, &iov, arg, i);
		if (ret)
			break;
		ret = io_buffer_validate(&iov);
		if (ret)
			break;
		if (!iov.iov_base && tag) {
			ret = -EINVAL;
			break;
		}

		ret = io_sqe_buffer_register(ctx, &iov, &ctx->user_bufs[i],
					     &last_hpage);
		if (ret)
			break;
		data->tags[i] = tag;
	}

	WARN_ON_ONCE(ctx->buf_data);

	ctx->buf_data = data;
	if (ret)
		__io_sqe_buffers_unregister(ctx);
	else
		io_rsrc_node_switch(ctx, NULL);
	return ret;


static void io_uring_clean_tctx(struct io_uring_task *tctx)
{
	struct io_tctx_node *node;
	unsigned long index;

	xa_for_each(&tctx->xa, index, node)
		io_uring_del_task_file(index);
	if (tctx->io_wq) {
		io_wq_put_and_exit(tctx->io_wq);
		tctx->io_wq = NULL;
	}


static bool io_poll_remove_one(struct io_kiocb *req)
	__must_hold(&req->ctx->completion_lock)
{
	bool do_complete;

	do_complete = io_poll_remove_waitqs(req);
	if (do_complete) {
		io_cqring_fill_event(req->ctx, req->user_data, -ECANCELED, 0);
		io_commit_cqring(req->ctx);
		req_set_fail_links(req);
		io_put_req_deferred(req, 1);
	}

	return do_complete;


static void io_destroy_buffers(struct io_ring_ctx *ctx)
{
	struct io_buffer *buf;
	unsigned long index;

	xa_for_each(&ctx->io_buffers, index, buf)
		__io_remove_buffers(ctx, buf, index, -1U);


	__must_hold(&req->ctx->completion_lock)
{
	struct io_timeout_data *io = req->async_data;

	if (hrtimer_try_to_cancel(&io->timer) != -1) {
		atomic_set(&req->ctx->cq_timeouts,
			atomic_read(&req->ctx->cq_timeouts) + 1);
		list_del_init(&req->timeout.list);
		io_cqring_fill_event(req->ctx, req->user_data, status, 0);
		io_put_req_deferred(req, 1);
	}
}


static inline bool io_req_needs_clean(struct io_kiocb *req)
{
	return req->flags & (REQ_F_BUFFER_SELECTED | REQ_F_NEED_CLEANUP |
				REQ_F_POLLED | REQ_F_INFLIGHT);
}


static int io_poll_add_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
	struct io_poll_iocb *poll = &req->poll;
	u32 flags;

	if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
		return -EINVAL;
	if (sqe->ioprio || sqe->buf_index || sqe->off || sqe->addr)
		return -EINVAL;
	flags = READ_ONCE(sqe->len);
	if (flags & ~IORING_POLL_ADD_MULTI)
		return -EINVAL;

	poll->events = io_poll_parse_events(sqe, flags);
	return 0;


static void io_iopoll_complete(struct io_ring_ctx *ctx, unsigned int *nr_events,
			       struct list_head *done)
{
	struct req_batch rb;
	struct io_kiocb *req;

	/* order with ->result store in io_complete_rw_iopoll() */
	smp_rmb();

	io_init_req_batch(&rb);
	while (!list_empty(done)) {
		int cflags = 0;

		req = list_first_entry(done, struct io_kiocb, inflight_entry);
		list_del(&req->inflight_entry);

		if (READ_ONCE(req->result) == -EAGAIN &&
		    !(req->flags & REQ_F_DONT_REISSUE)) {
			req->iopoll_completed = 0;
			req_ref_get(req);
			io_queue_async_work(req);
			continue;
		}

		if (req->flags & REQ_F_BUFFER_SELECTED)
			cflags = io_put_rw_kbuf(req);

		__io_cqring_fill_event(ctx, req->user_data, req->result, cflags);
		(*nr_events)++;

		if (req_ref_put_and_test(req))
			io_req_free_batch(&rb, req, &ctx->submit_state);
	}

	io_commit_cqring(ctx);
	io_cqring_ev_posted_iopoll(ctx);
	io_req_free_batch_finish(ctx, &rb);
}


static void __io_queue_proc(struct io_poll_iocb *poll, struct io_poll_table *pt,
			    struct wait_queue_head *head,
			    struct io_poll_iocb **poll_ptr)
{
	struct io_kiocb *req = pt->req;

	/*
	 * If poll->head is already set, it's because the file being polled
	 * uses multiple waitqueues for poll handling (eg one for read, one
	 * for write). Setup a separate io_poll_iocb if this happens.
	 */
	if (unlikely(poll->head)) {
		struct io_poll_iocb *poll_one = poll;

		/* already have a 2nd entry, fail a third attempt */
		if (*poll_ptr) {
			pt->error = -EINVAL;
			return;
		}
		/*
		 * Can't handle multishot for double wait for now, turn it
		 * into one-shot mode.
		 */
		if (!(req->poll.events & EPOLLONESHOT))
			req->poll.events |= EPOLLONESHOT;
		/* double add on the same waitqueue head, ignore */
		if (poll->head == head)
			return;
		poll = kmalloc(sizeof(*poll), GFP_ATOMIC);
		if (!poll) {
			pt->error = -ENOMEM;
			return;
		}
		io_init_poll_iocb(poll, poll_one->events, io_poll_double_wake);
		req_ref_get(req);
		poll->wait.private = req;
		*poll_ptr = poll;
	}

	pt->error = 0;
	poll->head = head;

	if (poll->events & EPOLLEXCLUSIVE)
		add_wait_queue_exclusive(head, &poll->wait);
	else
		add_wait_queue(head, &poll->wait);


static int io_uring_alloc_task_context(struct task_struct *task,
				       struct io_ring_ctx *ctx)
{
	struct io_uring_task *tctx;
	int ret;

	tctx = kmalloc(sizeof(*tctx), GFP_KERNEL);
	if (unlikely(!tctx))
		return -ENOMEM;

	ret = percpu_counter_init(&tctx->inflight, 0, GFP_KERNEL);
	if (unlikely(ret)) {
		kfree(tctx);
		return ret;
	}

	tctx->io_wq = io_init_wq_offload(ctx, task);
	if (IS_ERR(tctx->io_wq)) {
		ret = PTR_ERR(tctx->io_wq);
		percpu_counter_destroy(&tctx->inflight);
		kfree(tctx);
		return ret;
	}

	xa_init(&tctx->xa);
	init_waitqueue_head(&tctx->wait);
	tctx->last = NULL;
	atomic_set(&tctx->in_idle, 0);
	atomic_set(&tctx->inflight_tracked, 0);
	task->io_uring = tctx;
	spin_lock_init(&tctx->task_lock);
	INIT_WQ_LIST(&tctx->task_list);
	tctx->task_state = 0;
	init_task_work(&tctx->task_work, tctx_task_work);
	return 0;


static void io_req_free_batch(struct req_batch *rb, struct io_kiocb *req,
			      struct io_submit_state *state)
{
	io_queue_next(req);
	io_dismantle_req(req);

	if (req->task != rb->task) {
		if (rb->task)
			io_put_task(rb->task, rb->task_refs);
		rb->task = req->task;
		rb->task_refs = 0;
	}
	rb->task_refs++;
	rb->ctx_refs++;

	if (state->free_reqs != ARRAY_SIZE(state->reqs))
		state->reqs[state->free_reqs++] = req;
	else
		list_add(&req->compl.list, &state->comp.free_list);
}


static int io_sqe_buffer_register(struct io_ring_ctx *ctx, struct iovec *iov,
				  struct io_mapped_ubuf **pimu,
				  struct page **last_hpage)
{
	struct io_mapped_ubuf *imu = NULL;
	struct vm_area_struct **vmas = NULL;
	struct page **pages = NULL;
	unsigned long off, start, end, ubuf;
	size_t size;
	int ret, pret, nr_pages, i;

	if (!iov->iov_base) {
		*pimu = ctx->dummy_ubuf;
		return 0;
	}

	ubuf = (unsigned long) iov->iov_base;
	end = (ubuf + iov->iov_len + PAGE_SIZE - 1) >> PAGE_SHIFT;
	start = ubuf >> PAGE_SHIFT;
	nr_pages = end - start;

	*pimu = NULL;
	ret = -ENOMEM;

	pages = kvmalloc_array(nr_pages, sizeof(struct page *), GFP_KERNEL);
	if (!pages)
		goto done;

	vmas = kvmalloc_array(nr_pages, sizeof(struct vm_area_struct *),
			      GFP_KERNEL);
	if (!vmas)
		goto done;

	imu = kvmalloc(struct_size(imu, bvec, nr_pages), GFP_KERNEL);
	if (!imu)
		goto done;

	ret = 0;
	mmap_read_lock(current->mm);
	pret = pin_user_pages(ubuf, nr_pages, FOLL_WRITE | FOLL_LONGTERM,
			      pages, vmas);
	if (pret == nr_pages) {
		/* don't support file backed memory */
		for (i = 0; i < nr_pages; i++) {
			struct vm_area_struct *vma = vmas[i];

			if (vma->vm_file &&
			    !is_file_hugepages(vma->vm_file)) {
				ret = -EOPNOTSUPP;
				break;
			}
		}
	} else {
		ret = pret < 0 ? pret : -EFAULT;
	}
	mmap_read_unlock(current->mm);
	if (ret) {
		/*
		 * if we did partial map, or found file backed vmas,
		 * release any pages we did get
		 */
		if (pret > 0)
			unpin_user_pages(pages, pret);
		goto done;
	}

	ret = io_buffer_account_pin(ctx, pages, pret, imu, last_hpage);
	if (ret) {
		unpin_user_pages(pages, pret);
		goto done;
	}

	off = ubuf & ~PAGE_MASK;
	size = iov->iov_len;
	for (i = 0; i < nr_pages; i++) {
		size_t vec_len;

		vec_len = min_t(size_t, size, PAGE_SIZE - off);
		imu->bvec[i].bv_page = pages[i];
		imu->bvec[i].bv_len = vec_len;
		imu->bvec[i].bv_offset = off;
		off = 0;
		size -= vec_len;
	}
	/* store original address for later verification */
	imu->ubuf = ubuf;
	imu->ubuf_end = ubuf + iov->iov_len;
	imu->nr_bvecs = nr_pages;
	*pimu = imu;
	ret = 0;
done:
	if (ret)
		kvfree(imu);
	kvfree(pages);
	kvfree(vmas);
	return ret;


static inline bool io_should_trigger_evfd(struct io_ring_ctx *ctx)
{
	if (likely(!ctx->cq_ev_fd))
		return false;
	if (READ_ONCE(ctx->rings->cq_flags) & IORING_CQ_EVENTFD_DISABLED)
		return false;
	return !ctx->eventfd_async || io_wq_current_is_worker();
}


static int io_rsrc_ref_quiesce(struct io_rsrc_data *data, struct io_ring_ctx *ctx)
{
	int ret;

	/* As we may drop ->uring_lock, other task may have started quiesce */
	if (data->quiesce)
		return -ENXIO;

	data->quiesce = true;
	do {
		ret = io_rsrc_node_switch_start(ctx);
		if (ret)
			break;
		io_rsrc_node_switch(ctx, data);

		/* kill initial ref, already quiesced if zero */
		if (atomic_dec_and_test(&data->refs))
			break;
		flush_delayed_work(&ctx->rsrc_put_work);
		ret = wait_for_completion_interruptible(&data->done);
		if (!ret)
			break;

		atomic_inc(&data->refs);
		/* wait for all works potentially completing data->done */
		flush_delayed_work(&ctx->rsrc_put_work);
		reinit_completion(&data->done);

		mutex_unlock(&ctx->uring_lock);
		ret = io_run_task_work_sig();
		mutex_lock(&ctx->uring_lock);
	} while (ret >= 0);
	data->quiesce = false;

	return ret;


static int io_queue_rsrc_removal(struct io_rsrc_data *data, unsigned idx,
				 struct io_rsrc_node *node, void *rsrc)
{
	struct io_rsrc_put *prsrc;

	prsrc = kzalloc(sizeof(*prsrc), GFP_KERNEL);
	if (!prsrc)
		return -ENOMEM;

	prsrc->tag = data->tags[idx];
	prsrc->rsrc = rsrc;
	list_add(&prsrc->list, &node->rsrc_list);
	return 0;


static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries)
{
	unsigned int to_submit;
	int ret = 0;

	to_submit = io_sqring_entries(ctx);
	/* if we're handling multiple rings, cap submit size for fairness */
	if (cap_entries && to_submit > 8)
		to_submit = 8;

	if (!list_empty(&ctx->iopoll_list) || to_submit) {
		unsigned nr_events = 0;

		mutex_lock(&ctx->uring_lock);
		if (!list_empty(&ctx->iopoll_list))
			io_do_iopoll(ctx, &nr_events, 0);

		/*
		 * Don't submit if refs are dying, good for io_uring_register(),
		 * but also it is relied upon by io_ring_exit_work()
		 */
		if (to_submit && likely(!percpu_ref_is_dying(&ctx->refs)) &&
		    !(ctx->flags & IORING_SETUP_R_DISABLED))
			ret = io_submit_sqes(ctx, to_submit);
		mutex_unlock(&ctx->uring_lock);
	}

	if (!io_sqring_full(ctx) && wq_has_sleeper(&ctx->sqo_sq_wait))
		wake_up(&ctx->sqo_sq_wait);

	return ret;


static inline int io_alloc_async_data(struct io_kiocb *req)
{
	WARN_ON_ONCE(!io_op_defs[req->opcode].async_size);
	req->async_data = kmalloc(io_op_defs[req->opcode].async_size, GFP_KERNEL);
	return req->async_data == NULL;
}


static int io_remove_buffers(struct io_kiocb *req, unsigned int issue_flags)
{
	struct io_provide_buf *p = &req->pbuf;
	struct io_ring_ctx *ctx = req->ctx;
	struct io_buffer *head;
	int ret = 0;
	bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;

	io_ring_submit_lock(ctx, !force_nonblock);

	lockdep_assert_held(&ctx->uring_lock);

	ret = -ENOENT;
	head = xa_load(&ctx->io_buffers, p->bgid);
	if (head)
		ret = __io_remove_buffers(ctx, head, p->bgid, p->nbufs);
	if (ret < 0)
		req_set_fail_links(req);

	/* complete before unlock, IOPOLL may need the lock */
	__io_req_complete(req, issue_flags, ret, 0);
	io_ring_submit_unlock(ctx, !force_nonblock);
	return 0;
}


static int __io_register_rsrc_update(struct io_ring_ctx *ctx, unsigned type,
				     struct io_uring_rsrc_update2 *up,
				     unsigned nr_args)
{
	__u32 tmp;
	int err;

	if (up->resv)
		return -EINVAL;
	if (check_add_overflow(up->offset, nr_args, &tmp))
		return -EOVERFLOW;
	err = io_rsrc_node_switch_start(ctx);
	if (err)
		return err;

	switch (type) {
	case IORING_RSRC_FILE:
		return __io_sqe_files_update(ctx, up, nr_args);
	case IORING_RSRC_BUFFER:
		return __io_sqe_buffers_update(ctx, up, nr_args);
	}
	return -EINVAL;


static void io_rsrc_node_destroy(struct io_rsrc_node *ref_node)
{
	percpu_ref_exit(&ref_node->refs);
	kfree(ref_node);


static int io_poll_double_wake(struct wait_queue_entry *wait, unsigned mode,
			       int sync, void *key)
{
	struct io_kiocb *req = wait->private;
	struct io_poll_iocb *poll = io_poll_get_single(req);
	__poll_t mask = key_to_poll(key);

	/* for instances that support it check for an event match first: */
	if (mask && !(mask & poll->events))
		return 0;
	if (!(poll->events & EPOLLONESHOT))
		return poll->wait.func(&poll->wait, mode, sync, key);

	list_del_init(&wait->entry);

	if (poll && poll->head) {
		bool done;

		spin_lock(&poll->head->lock);
		done = list_empty(&poll->wait.entry);
		if (!done)
			list_del_init(&poll->wait.entry);
		/* make sure double remove sees this as being gone */
		wait->private = NULL;
		spin_unlock(&poll->head->lock);
		if (!done) {
			/* use wait func handler, so it matches the rq type */
			poll->wait.func(&poll->wait, mode, sync, key);
		}
	}
	req_ref_put(req);
	return 1;


static enum hrtimer_restart io_timeout_fn(struct hrtimer *timer)
{
	struct io_timeout_data *data = container_of(timer,
						struct io_timeout_data, timer);
	struct io_kiocb *req = data->req;
	struct io_ring_ctx *ctx = req->ctx;
	unsigned long flags;

	spin_lock_irqsave(&ctx->completion_lock, flags);
	list_del_init(&req->timeout.list);
	atomic_set(&req->ctx->cq_timeouts,
		atomic_read(&req->ctx->cq_timeouts) + 1);

	io_cqring_fill_event(ctx, req->user_data, -ETIME, 0);
	io_commit_cqring(ctx);
	spin_unlock_irqrestore(&ctx->completion_lock, flags);

	io_cqring_ev_posted(ctx);
	req_set_fail_links(req);
	io_put_req(req);
	return HRTIMER_NORESTART;


static void io_sqd_update_thread_idle(struct io_sq_data *sqd)
{
	struct io_ring_ctx *ctx;
	unsigned sq_thread_idle = 0;

	list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
		sq_thread_idle = max(sq_thread_idle, ctx->sq_thread_idle);
	sqd->sq_thread_idle = sq_thread_idle;


static int io_submit_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req,
			 const struct io_uring_sqe *sqe)
{
	struct io_submit_link *link = &ctx->submit_state.link;
	int ret;

	ret = io_init_req(ctx, req, sqe);
	if (unlikely(ret)) {
fail_req:
		if (link->head) {
			/* fail even hard links since we don't submit */
			link->head->flags |= REQ_F_FAIL_LINK;
			io_req_complete_failed(link->head, -ECANCELED);
			link->head = NULL;
		}
		io_req_complete_failed(req, ret);
		return ret;
	}
	ret = io_req_prep(req, sqe);
	if (unlikely(ret))
		goto fail_req;

	/* don't need @sqe from now on */
	trace_io_uring_submit_sqe(ctx, req->opcode, req->user_data,
				true, ctx->flags & IORING_SETUP_SQPOLL);

	/*
	 * If we already have a head request, queue this one for async
	 * submittal once the head completes. If we don't have a head but
	 * IOSQE_IO_LINK is set in the sqe, start a new head. This one will be
	 * submitted sync once the chain is complete. If none of those
	 * conditions are true (normal request), then just queue it.
	 */
	if (link->head) {
		struct io_kiocb *head = link->head;

		/*
		 * Taking sequential execution of a link, draining both sides
		 * of the link also fullfils IOSQE_IO_DRAIN semantics for all
		 * requests in the link. So, it drains the head and the
		 * next after the link request. The last one is done via
		 * drain_next flag to persist the effect across calls.
		 */
		if (req->flags & REQ_F_IO_DRAIN) {
			head->flags |= REQ_F_IO_DRAIN;
			ctx->drain_next = 1;
		}
		ret = io_req_prep_async(req);
		if (unlikely(ret))
			goto fail_req;
		trace_io_uring_link(ctx, req, head);
		link->last->link = req;
		link->last = req;

		/* last request of a link, enqueue the link */
		if (!(req->flags & (REQ_F_LINK | REQ_F_HARDLINK))) {
			io_queue_sqe(head);
			link->head = NULL;
		}
	} else {
		if (unlikely(ctx->drain_next)) {
			req->flags |= REQ_F_IO_DRAIN;
			ctx->drain_next = 0;
		}
		if (req->flags & (REQ_F_LINK | REQ_F_HARDLINK)) {
			link->head = req;
			link->last = req;
		} else {
			io_queue_sqe(req);
		}
	}

	return 0;

#define SQE_VALID_FLAGS	(IOSQE_FIXED_FILE|IOSQE_IO_DRAIN|IOSQE_IO_LINK|	\
				IOSQE_IO_HARDLINK | IOSQE_ASYNC | \
				IOSQE_BUFFER_SELECT)

struct io_uring {
	u32 head ____cacheline_aligned_in_smp;
	u32 tail ____cacheline_aligned_in_smp;
}

struct io_rings {
	/*
	 * Head and tail offsets into the ring; the offsets need to be
	 * masked to get valid indices.
	 *
	 * The kernel controls head of the sq ring and the tail of the cq ring,
	 * and the application controls tail of the sq ring and the head of the
	 * cq ring.
	 */
	struct io_uring		sq, cq;
	/*
	 * Bitmasks to apply to head and tail offsets (constant, equals
	 * ring_entries - 1)
	 */
	u32			sq_ring_mask, cq_ring_mask;
	/* Ring sizes (constant, power of 2) */
	u32			sq_ring_entries, cq_ring_entries;
	/*
	 * Number of invalid entries dropped by the kernel due to
	 * invalid index stored in array
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * After a new SQ head value was read by the application this
	 * counter includes all submissions that were dropped reaching
	 * the new SQ head (and possibly more).
	 */
	u32			sq_dropped;
	/*
	 * Runtime SQ flags
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application.
	 *
	 * The application needs a full memory barrier before checking
	 * for IORING_SQ_NEED_WAKEUP after updating the sq tail.
	 */
	u32			sq_flags;
	/*
	 * Runtime CQ flags
	 *
	 * Written by the application, shouldn't be modified by the
	 * kernel.
	 */
	u32                     cq_flags;
	/*
	 * Number of completion events lost because the queue was full;
	 * this should be avoided by the application by making sure
	 * there are not more requests pending than there is space in
	 * the completion queue.
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * As completion events come in out of order this counter is not
	 * ordered with any other data.
	 */
	u32			cq_overflow;
	/*
	 * Ring buffer of completion events.
	 *
	 * The kernel writes completion events fresh every time they are
	 * produced, so the application is allowed to modify pending
	 * entries.
	 */
	struct io_uring_cqe	cqes[] ____cacheline_aligned_in_smp;
}

struct io_mapped_ubuf {
	u64		ubuf;
	u64		ubuf_end;
	unsigned int	nr_bvecs;
	unsigned long	acct_pages;
	struct bio_vec	bvec[];
}

struct io_ring_ctx

struct io_overflow_cqe {
	struct io_uring_cqe cqe;
	struct list_head list;
}

struct io_fixed_file {
	/* file * with additional FFS_* flags */
	unsigned long file_ptr;
}

struct io_rsrc_put {
	struct list_head list;
	u64 tag;
	union {
		void *rsrc;
		struct file *file;
		struct io_mapped_ubuf *buf;
	};
}

struct io_file_table {
	/* two level table */
	struct io_fixed_file **files;
}


static int io_req_prep_async(struct io_kiocb *req)
{
	if (!io_op_defs[req->opcode].needs_async_setup)
		return 0;
	if (WARN_ON_ONCE(req->async_data))
		return -EFAULT;
	if (io_alloc_async_data(req))
		return -EAGAIN;

	switch (req->opcode) {
	case IORING_OP_READV:
		return io_rw_prep_async(req, READ);
	case IORING_OP_WRITEV:
		return io_rw_prep_async(req, WRITE);
	case IORING_OP_SENDMSG:
		return io_sendmsg_prep_async(req);
	case IORING_OP_RECVMSG:
		return io_recvmsg_prep_async(req);
	case IORING_OP_CONNECT:
		return io_connect_prep_async(req);
	}
	printk_once(KERN_WARNING "io_uring: prep_async() bad opcode %d\n",
		    req->opcode);
	return -EFAULT;


				 struct io_poll_iocb *poll, bool do_cancel)
	__must_hold(&req->ctx->completion_lock)
{
	bool do_complete = false;

	if (!poll->head)
		return false;
	spin_lock(&poll->head->lock);
	if (do_cancel)
		WRITE_ONCE(poll->canceled, true);
	if (!list_empty(&poll->wait.entry)) {
		list_del_init(&poll->wait.entry);
		do_complete = true;
	}
	spin_unlock(&poll->head->lock);
	hash_del(&req->hash_node);
	return do_complete;


static bool io_arm_poll_handler(struct io_kiocb *req)
{
	const struct io_op_def *def = &io_op_defs[req->opcode];
	struct io_ring_ctx *ctx = req->ctx;
	struct async_poll *apoll;
	struct io_poll_table ipt;
	__poll_t mask, ret;
	int rw;

	if (!req->file || !file_can_poll(req->file))
		return false;
	if (req->flags & REQ_F_POLLED)
		return false;
	if (def->pollin)
		rw = READ;
	else if (def->pollout)
		rw = WRITE;
	else
		return false;
	/* if we can't nonblock try, then no point in arming a poll handler */
	if (!io_file_supports_async(req, rw))
		return false;

	apoll = kmalloc(sizeof(*apoll), GFP_ATOMIC);
	if (unlikely(!apoll))
		return false;
	apoll->double_poll = NULL;

	req->flags |= REQ_F_POLLED;
	req->apoll = apoll;

	mask = EPOLLONESHOT;
	if (def->pollin)
		mask |= POLLIN | POLLRDNORM;
	if (def->pollout)
		mask |= POLLOUT | POLLWRNORM;

	/* If reading from MSG_ERRQUEUE using recvmsg, ignore POLLIN */
	if ((req->opcode == IORING_OP_RECVMSG) &&
	    (req->sr_msg.msg_flags & MSG_ERRQUEUE))
		mask &= ~POLLIN;

	mask |= POLLERR | POLLPRI;

	ipt.pt._qproc = io_async_queue_proc;

	ret = __io_arm_poll_handler(req, &apoll->poll, &ipt, mask,
					io_async_wake);
	if (ret || ipt.error) {
		io_poll_remove_double(req);
		spin_unlock_irq(&ctx->completion_lock);
		return false;
	}
	spin_unlock_irq(&ctx->completion_lock);
	trace_io_uring_poll_arm(ctx, req->opcode, req->user_data, mask,
					apoll->poll.events);
	return true;


static void io_req_task_work_add_fallback(struct io_kiocb *req,
					  task_work_func_t cb)
{
	init_task_work(&req->task_work, cb);
	io_task_work_add_head(&req->ctx->exit_task_work, &req->task_work);
}


static int io_uring_create(unsigned entries, struct io_uring_params *p,
			   struct io_uring_params __user *params)
{
	struct io_ring_ctx *ctx;
	struct file *file;
	int ret;

	if (!entries)
		return -EINVAL;
	if (entries > IORING_MAX_ENTRIES) {
		if (!(p->flags & IORING_SETUP_CLAMP))
			return -EINVAL;
		entries = IORING_MAX_ENTRIES;
	}

	/*
	 * Use twice as many entries for the CQ ring. It's possible for the
	 * application to drive a higher depth than the size of the SQ ring,
	 * since the sqes are only used at submission time. This allows for
	 * some flexibility in overcommitting a bit. If the application has
	 * set IORING_SETUP_CQSIZE, it will have passed in the desired number
	 * of CQ ring entries manually.
	 */
	p->sq_entries = roundup_pow_of_two(entries);
	if (p->flags & IORING_SETUP_CQSIZE) {
		/*
		 * If IORING_SETUP_CQSIZE is set, we do the same roundup
		 * to a power-of-two, if it isn't already. We do NOT impose
		 * any cq vs sq ring sizing.
		 */
		if (!p->cq_entries)
			return -EINVAL;
		if (p->cq_entries > IORING_MAX_CQ_ENTRIES) {
			if (!(p->flags & IORING_SETUP_CLAMP))
				return -EINVAL;
			p->cq_entries = IORING_MAX_CQ_ENTRIES;
		}
		p->cq_entries = roundup_pow_of_two(p->cq_entries);
		if (p->cq_entries < p->sq_entries)
			return -EINVAL;
	} else {
		p->cq_entries = 2 * p->sq_entries;
	}

	ctx = io_ring_ctx_alloc(p);
	if (!ctx)
		return -ENOMEM;
	ctx->compat = in_compat_syscall();
	if (!capable(CAP_IPC_LOCK))
		ctx->user = get_uid(current_user());

	/*
	 * This is just grabbed for accounting purposes. When a process exits,
	 * the mm is exited and dropped before the files, hence we need to hang
	 * on to this mm purely for the purposes of being able to unaccount
	 * memory (locked/pinned vm). It's not used for anything else.
	 */
	mmgrab(current->mm);
	ctx->mm_account = current->mm;

	ret = io_allocate_scq_urings(ctx, p);
	if (ret)
		goto err;

	ret = io_sq_offload_create(ctx, p);
	if (ret)
		goto err;
	/* always set a rsrc node */
	ret = io_rsrc_node_switch_start(ctx);
	if (ret)
		goto err;
	io_rsrc_node_switch(ctx, NULL);

	memset(&p->sq_off, 0, sizeof(p->sq_off));
	p->sq_off.head = offsetof(struct io_rings, sq.head);
	p->sq_off.tail = offsetof(struct io_rings, sq.tail);
	p->sq_off.ring_mask = offsetof(struct io_rings, sq_ring_mask);
	p->sq_off.ring_entries = offsetof(struct io_rings, sq_ring_entries);
	p->sq_off.flags = offsetof(struct io_rings, sq_flags);
	p->sq_off.dropped = offsetof(struct io_rings, sq_dropped);
	p->sq_off.array = (char *)ctx->sq_array - (char *)ctx->rings;

	memset(&p->cq_off, 0, sizeof(p->cq_off));
	p->cq_off.head = offsetof(struct io_rings, cq.head);
	p->cq_off.tail = offsetof(struct io_rings, cq.tail);
	p->cq_off.ring_mask = offsetof(struct io_rings, cq_ring_mask);
	p->cq_off.ring_entries = offsetof(struct io_rings, cq_ring_entries);
	p->cq_off.overflow = offsetof(struct io_rings, cq_overflow);
	p->cq_off.cqes = offsetof(struct io_rings, cqes);
	p->cq_off.flags = offsetof(struct io_rings, cq_flags);

	p->features = IORING_FEAT_SINGLE_MMAP | IORING_FEAT_NODROP |
			IORING_FEAT_SUBMIT_STABLE | IORING_FEAT_RW_CUR_POS |
			IORING_FEAT_CUR_PERSONALITY | IORING_FEAT_FAST_POLL |
			IORING_FEAT_POLL_32BITS | IORING_FEAT_SQPOLL_NONFIXED |
			IORING_FEAT_EXT_ARG | IORING_FEAT_NATIVE_WORKERS;

	if (copy_to_user(params, p, sizeof(*p))) {
		ret = -EFAULT;
		goto err;
	}

	file = io_uring_get_file(ctx);
	if (IS_ERR(file)) {
		ret = PTR_ERR(file);
		goto err;
	}

	/*
	 * Install ring fd as the very last thing, so we don't risk someone
	 * having closed it before we finish setup
	 */
	ret = io_uring_install_fd(ctx, file);
	if (ret < 0) {
		/* fput will clean it up */
		fput(file);
		return ret;
	}

	trace_io_uring_create(ret, ctx, p->sq_entries, p->cq_entries, p->flags);
	return ret;
err:
	io_ring_ctx_wait_and_kill(ctx);
	return ret;

#define IORING_MAX_ENTRIES	32768

#define IORING_MAX_CQ_ENTRIES	(2 * IORING_MAX_ENTRIES)

struct io_uring {
	u32 head ____cacheline_aligned_in_smp;
	u32 tail ____cacheline_aligned_in_smp;
}

struct io_rings {
	/*
	 * Head and tail offsets into the ring; the offsets need to be
	 * masked to get valid indices.
	 *
	 * The kernel controls head of the sq ring and the tail of the cq ring,
	 * and the application controls tail of the sq ring and the head of the
	 * cq ring.
	 */
	struct io_uring		sq, cq;
	/*
	 * Bitmasks to apply to head and tail offsets (constant, equals
	 * ring_entries - 1)
	 */
	u32			sq_ring_mask, cq_ring_mask;
	/* Ring sizes (constant, power of 2) */
	u32			sq_ring_entries, cq_ring_entries;
	/*
	 * Number of invalid entries dropped by the kernel due to
	 * invalid index stored in array
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * After a new SQ head value was read by the application this
	 * counter includes all submissions that were dropped reaching
	 * the new SQ head (and possibly more).
	 */
	u32			sq_dropped;
	/*
	 * Runtime SQ flags
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application.
	 *
	 * The application needs a full memory barrier before checking
	 * for IORING_SQ_NEED_WAKEUP after updating the sq tail.
	 */
	u32			sq_flags;
	/*
	 * Runtime CQ flags
	 *
	 * Written by the application, shouldn't be modified by the
	 * kernel.
	 */
	u32                     cq_flags;
	/*
	 * Number of completion events lost because the queue was full;
	 * this should be avoided by the application by making sure
	 * there are not more requests pending than there is space in
	 * the completion queue.
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * As completion events come in out of order this counter is not
	 * ordered with any other data.
	 */
	u32			cq_overflow;
	/*
	 * Ring buffer of completion events.
	 *
	 * The kernel writes completion events fresh every time they are
	 * produced, so the application is allowed to modify pending
	 * entries.
	 */
	struct io_uring_cqe	cqes[] ____cacheline_aligned_in_smp;
}

struct io_mapped_ubuf {
	u64		ubuf;
	u64		ubuf_end;
	unsigned int	nr_bvecs;
	unsigned long	acct_pages;
	struct bio_vec	bvec[];
}

struct io_ring_ctx

struct io_overflow_cqe {
	struct io_uring_cqe cqe;
	struct list_head list;
}

struct io_fixed_file {
	/* file * with additional FFS_* flags */
	unsigned long file_ptr;
}

struct io_rsrc_put {
	struct list_head list;
	u64 tag;
	union {
		void *rsrc;
		struct file *file;
		struct io_mapped_ubuf *buf;
	};
}

struct io_file_table {
	/* two level table */
	struct io_fixed_file **files;
}


	__must_hold(&req->ctx->completion_lock)
{
	bool posted = false;

	if (likely(req->flags & REQ_F_LINK_TIMEOUT))
		posted = io_kill_linked_timeout(req);
	if (unlikely((req->flags & REQ_F_FAIL_LINK) &&
		     !(req->flags & REQ_F_HARDLINK))) {
		posted |= (req->link != NULL);
		io_fail_links(req);
	}
	return posted;
}

struct io_rings {
	/*
	 * Head and tail offsets into the ring; the offsets need to be
	 * masked to get valid indices.
	 *
	 * The kernel controls head of the sq ring and the tail of the cq ring,
	 * and the application controls tail of the sq ring and the head of the
	 * cq ring.
	 */
	struct io_uring		sq, cq;
	/*
	 * Bitmasks to apply to head and tail offsets (constant, equals
	 * ring_entries - 1)
	 */
	u32			sq_ring_mask, cq_ring_mask;
	/* Ring sizes (constant, power of 2) */
	u32			sq_ring_entries, cq_ring_entries;
	/*
	 * Number of invalid entries dropped by the kernel due to
	 * invalid index stored in array
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * After a new SQ head value was read by the application this
	 * counter includes all submissions that were dropped reaching
	 * the new SQ head (and possibly more).
	 */
	u32			sq_dropped;
	/*
	 * Runtime SQ flags
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application.
	 *
	 * The application needs a full memory barrier before checking
	 * for IORING_SQ_NEED_WAKEUP after updating the sq tail.
	 */
	u32			sq_flags;
	/*
	 * Runtime CQ flags
	 *
	 * Written by the application, shouldn't be modified by the
	 * kernel.
	 */
	u32                     cq_flags;
	/*
	 * Number of completion events lost because the queue was full;
	 * this should be avoided by the application by making sure
	 * there are not more requests pending than there is space in
	 * the completion queue.
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * As completion events come in out of order this counter is not
	 * ordered with any other data.
	 */
	u32			cq_overflow;
	/*
	 * Ring buffer of completion events.
	 *
	 * The kernel writes completion events fresh every time they are
	 * produced, so the application is allowed to modify pending
	 * entries.
	 */
	struct io_uring_cqe	cqes[] ____cacheline_aligned_in_smp;
}

struct io_fixed_file {
	/* file * with additional FFS_* flags */
	unsigned long file_ptr;
}

struct io_rsrc_node {
	struct percpu_ref		refs;
	struct list_head		node;
	struct list_head		rsrc_list;
	struct io_rsrc_data		*rsrc_data;
	struct llist_node		llist;
	bool				done;
}

typedef void (rsrc_put_fn)(struct io_ring_ctx *ctx, struct io_rsrc_put *prsrc);

struct io_rsrc_data {
	struct io_ring_ctx		*ctx;

	u64				*tags;
	rsrc_put_fn			*do_put;
	atomic_t			refs;
	struct completion		done;
	bool				quiesce;
}

struct io_restriction {
	DECLARE_BITMAP(register_op, IORING_REGISTER_LAST);
	DECLARE_BITMAP(sqe_op, IORING_OP_LAST);
	u8 sqe_flags_allowed;
	u8 sqe_flags_required;
	bool registered;
}


static int io_provide_buffers(struct io_kiocb *req, unsigned int issue_flags)
{
	struct io_provide_buf *p = &req->pbuf;
	struct io_ring_ctx *ctx = req->ctx;
	struct io_buffer *head, *list;
	int ret = 0;
	bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;

	io_ring_submit_lock(ctx, !force_nonblock);

	lockdep_assert_held(&ctx->uring_lock);

	list = head = xa_load(&ctx->io_buffers, p->bgid);

	ret = io_add_buffers(p, &head);
	if (ret >= 0 && !list) {
		ret = xa_insert(&ctx->io_buffers, p->bgid, head, GFP_KERNEL);
		if (ret < 0)
			__io_remove_buffers(ctx, head, p->bgid, -1U);
	}
	if (ret < 0)
		req_set_fail_links(req);
	/* complete before unlock, IOPOLL may need the lock */
	__io_req_complete(req, issue_flags, ret, 0);
	io_ring_submit_unlock(ctx, !force_nonblock);
	return 0;
}


			     struct timespec64 *ts, enum hrtimer_mode mode)
	__must_hold(&ctx->completion_lock)
{
	struct io_kiocb *req = io_timeout_extract(ctx, user_data);
	struct io_timeout_data *data;

	if (IS_ERR(req))
		return PTR_ERR(req);

	req->timeout.off = 0; /* noseq */
	data = req->async_data;
	list_add_tail(&req->timeout.list, &ctx->timeout_list);
	hrtimer_init(&data->timer, CLOCK_MONOTONIC, mode);
	data->timer.function = io_timeout_fn;
	hrtimer_start(&data->timer, timespec64_to_ktime(*ts), mode);
	return 0;

struct io_uring {
	u32 head ____cacheline_aligned_in_smp;
	u32 tail ____cacheline_aligned_in_smp;
}

struct io_rings {
	/*
	 * Head and tail offsets into the ring; the offsets need to be
	 * masked to get valid indices.
	 *
	 * The kernel controls head of the sq ring and the tail of the cq ring,
	 * and the application controls tail of the sq ring and the head of the
	 * cq ring.
	 */
	struct io_uring		sq, cq;
	/*
	 * Bitmasks to apply to head and tail offsets (constant, equals
	 * ring_entries - 1)
	 */
	u32			sq_ring_mask, cq_ring_mask;
	/* Ring sizes (constant, power of 2) */
	u32			sq_ring_entries, cq_ring_entries;
	/*
	 * Number of invalid entries dropped by the kernel due to
	 * invalid index stored in array
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * After a new SQ head value was read by the application this
	 * counter includes all submissions that were dropped reaching
	 * the new SQ head (and possibly more).
	 */
	u32			sq_dropped;
	/*
	 * Runtime SQ flags
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application.
	 *
	 * The application needs a full memory barrier before checking
	 * for IORING_SQ_NEED_WAKEUP after updating the sq tail.
	 */
	u32			sq_flags;
	/*
	 * Runtime CQ flags
	 *
	 * Written by the application, shouldn't be modified by the
	 * kernel.
	 */
	u32			cq_flags;
	/*
	 * Number of completion events lost because the queue was full;
	 * this should be avoided by the application by making sure
	 * there are not more requests pending than there is space in
	 * the completion queue.
	 *
	 * Written by the kernel, shouldn't be modified by the
	 * application (i.e. get number of "new events" by comparing to
	 * cached value).
	 *
	 * As completion events come in out of order this counter is not
	 * ordered with any other data.
	 */
	u32			cq_overflow;
	/*
	 * Ring buffer of completion events.
	 *
	 * The kernel writes completion events fresh every time they are
	 * produced, so the application is allowed to modify pending
	 * entries.
	 */
	struct io_uring_cqe	cqes[] ____cacheline_aligned_in_smp;
}

enum io_uring_cmd_flags {
	IO_URING_F_NONBLOCK		= 1,
	IO_URING_F_COMPLETE_DEFER	= 2,
}

struct io_mapped_ubuf {
	u64		ubuf;
	u64		ubuf_end;
	unsigned int	nr_bvecs;
	unsigned long	acct_pages;
	struct bio_vec	bvec[];
}

struct io_ring_ctx

struct io_overflow_cqe {
	struct io_uring_cqe cqe;
	struct list_head list;
}

struct io_fixed_file {
	/* file * with additional FFS_* flags */
	unsigned long file_ptr;
}

struct io_rsrc_put {
	struct list_head list;
	u64 tag;
	union {
		void *rsrc;
		struct file *file;
		struct io_mapped_ubuf *buf;
	};
}

struct io_file_table {
	/* two level table */
	struct io_fixed_file **files;
}


static void io_sq_thread_unpark(struct io_sq_data *sqd)
	__releases(&sqd->lock)
{
	WARN_ON_ONCE(sqd->thread == current);

	/*
	 * Do the dance but not conditional clear_bit() because it'd race with
	 * other threads incrementing park_pending and setting the bit.
	 */
	clear_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
	if (atomic_dec_return(&sqd->park_pending))
		set_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
	mutex_unlock(&sqd->lock);


/* Returns true if we found and killed one or more timeouts */
static bool io_kill_timeouts(struct io_ring_ctx *ctx, struct task_struct *tsk,
			     struct files_struct *files)
{
	struct io_kiocb *req, *tmp;
	int canceled = 0;

	spin_lock_irq(&ctx->completion_lock);
	list_for_each_entry_safe(req, tmp, &ctx->timeout_list, timeout.list) {
		if (io_match_task(req, tsk, files)) {
			io_kill_timeout(req, -ECANCELED);
			canceled++;
		}
	}
	if (canceled != 0)
		io_commit_cqring(ctx);
	spin_unlock_irq(&ctx->completion_lock);
	if (canceled != 0)
		io_cqring_ev_posted(ctx);
	return canceled != 0;


static bool io_uring_try_cancel_iowq(struct io_ring_ctx *ctx)
{
	struct io_tctx_node *node;
	enum io_wq_cancel cret;
	bool ret = false;

	mutex_lock(&ctx->uring_lock);
	list_for_each_entry(node, &ctx->tctx_list, ctx_node) {
		struct io_uring_task *tctx = node->task->io_uring;

		/*
		 * io_wq will stay alive while we hold uring_lock, because it's
		 * killed after ctx nodes, which requires to take the lock.
		 */
		if (!tctx || !tctx->io_wq)
			continue;
		cret = io_wq_cancel_cb(tctx->io_wq, io_cancel_ctx_cb, ctx, true);
		ret |= (cret != IO_WQ_CANCEL_NOTFOUND);
	}
	mutex_unlock(&ctx->uring_lock);

	return ret;


static void io_submit_flush_completions(struct io_comp_state *cs,
					struct io_ring_ctx *ctx)
{
	int i, nr = cs->nr;
	struct io_kiocb *req;
	struct req_batch rb;

	io_init_req_batch(&rb);
	spin_lock_irq(&ctx->completion_lock);
	for (i = 0; i < nr; i++) {
		req = cs->reqs[i];
		__io_cqring_fill_event(ctx, req->user_data, req->result,
					req->compl.cflags);
	}
	io_commit_cqring(ctx);
	spin_unlock_irq(&ctx->completion_lock);

	io_cqring_ev_posted(ctx);
	for (i = 0; i < nr; i++) {
		req = cs->reqs[i];

		/* submission and completion refs */
		if (req_ref_sub_and_test(req, 2))
			io_req_free_batch(&rb, req, &ctx->submit_state);
	}

	io_req_free_batch_finish(ctx, &rb);
	cs->nr = 0;
}


static void io_dismantle_req(struct io_kiocb *req)
{
	unsigned int flags = req->flags;

	if (io_req_needs_clean(req))
		io_clean_op(req);
	if (!(flags & REQ_F_FIXED_FILE))
		io_put_file(req->file);
	if (req->fixed_rsrc_refs)
		percpu_ref_put(req->fixed_rsrc_refs);
	if (req->async_data)
		kfree(req->async_data);
	if (req->work.creds) {
		put_cred(req->work.creds);
		req->work.creds = NULL;
	}
}


static void io_sq_thread_park(struct io_sq_data *sqd)
	__acquires(&sqd->lock)
{
	WARN_ON_ONCE(sqd->thread == current);

	atomic_inc(&sqd->park_pending);
	set_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
	mutex_lock(&sqd->lock);
	if (sqd->thread)
		wake_up_process(sqd->thread);


static bool io_run_task_work_head(struct callback_head **work_head)
{
	struct callback_head *work, *next;
	bool executed = false;

	do {
		work = xchg(work_head, NULL);
		if (!work)
			break;

		do {
			next = work->next;
			work->func(work);
			work = next;
			cond_resched();
		} while (work);
		executed = true;
	} while (1);

	return executed;
}


static void io_uring_try_cancel(struct files_struct *files)
{
	struct io_uring_task *tctx = current->io_uring;
	struct io_tctx_node *node;
	unsigned long index;

	xa_for_each(&tctx->xa, index, node) {
		struct io_ring_ctx *ctx = node->ctx;

		/* sqpoll task will cancel all its requests */
		if (!ctx->sq_data)
			io_uring_try_cancel_requests(ctx, current, files);
	}


static int io_poll_update(struct io_kiocb *req, unsigned int issue_flags)
{
	struct io_ring_ctx *ctx = req->ctx;
	struct io_kiocb *preq;
	bool completing;
	int ret;

	spin_lock_irq(&ctx->completion_lock);
	preq = io_poll_find(ctx, req->poll_update.old_user_data, true);
	if (!preq) {
		ret = -ENOENT;
		goto err;
	}

	if (!req->poll_update.update_events && !req->poll_update.update_user_data) {
		completing = true;
		ret = io_poll_remove_one(preq) ? 0 : -EALREADY;
		goto err;
	}

	/*
	 * Don't allow racy completion with singleshot, as we cannot safely
	 * update those. For multishot, if we're racing with completion, just
	 * let completion re-add it.
	 */
	completing = !__io_poll_remove_one(preq, &preq->poll, false);
	if (completing && (preq->poll.events & EPOLLONESHOT)) {
		ret = -EALREADY;
		goto err;
	}
	/* we now have a detached poll request. reissue. */
	ret = 0;
err:
	if (ret < 0) {
		spin_unlock_irq(&ctx->completion_lock);
		req_set_fail_links(req);
		io_req_complete(req, ret);
		return 0;
	}
	/* only mask one event flags, keep behavior flags */
	if (req->poll_update.update_events) {
		preq->poll.events &= ~0xffff;
		preq->poll.events |= req->poll_update.events & 0xffff;
		preq->poll.events |= IO_POLL_UNMASK;
	}
	if (req->poll_update.update_user_data)
		preq->user_data = req->poll_update.new_user_data;
	spin_unlock_irq(&ctx->completion_lock);

	/* complete update request, we're done with it */
	io_req_complete(req, ret);

	if (!completing) {
		ret = io_poll_add(preq, issue_flags);
		if (ret < 0) {
			req_set_fail_links(preq);
			io_req_complete(preq, ret);
		}
	}
	return 0;


static bool io_cancel_defer_files(struct io_ring_ctx *ctx,
				  struct task_struct *task,
				  struct files_struct *files)
{
	struct io_defer_entry *de;
	LIST_HEAD(list);

	spin_lock_irq(&ctx->completion_lock);
	list_for_each_entry_reverse(de, &ctx->defer_list, list) {
		if (io_match_task(de->req, task, files)) {
			list_cut_position(&list, &ctx->defer_list, &de->list);
			break;
		}
	}
	spin_unlock_irq(&ctx->completion_lock);
	if (list_empty(&list))
		return false;

	while (!list_empty(&list)) {
		de = list_first_entry(&list, struct io_defer_entry, list);
		list_del_init(&de->list);
		io_req_complete_failed(de->req, -ECANCELED);
		kfree(de);
	}
	return true;


static void io_flush_timeouts(struct io_ring_ctx *ctx)
{
	u32 seq;

	if (list_empty(&ctx->timeout_list))
		return;

	seq = ctx->cached_cq_tail - atomic_read(&ctx->cq_timeouts);

	do {
		u32 events_needed, events_got;
		struct io_kiocb *req = list_first_entry(&ctx->timeout_list,
						struct io_kiocb, timeout.list);

		if (io_is_timeout_noseq(req))
			break;

		/*
		 * Since seq can easily wrap around over time, subtract
		 * the last seq at which timeouts were flushed before comparing.
		 * Assuming not more than 2^31-1 events have happened since,
		 * these subtractions won't have wrapped, so we can check if
		 * target is in [last_seq, current_seq] by comparing the two.
		 */
		events_needed = req->timeout.target_seq - ctx->cq_last_tm_flush;
		events_got = seq - ctx->cq_last_tm_flush;
		if (events_got < events_needed)
			break;

		list_del_init(&req->timeout.list);
		io_kill_timeout(req, 0);
	} while (!list_empty(&ctx->timeout_list));

	ctx->cq_last_tm_flush = seq;
}


static inline void io_put_file(struct file *file)
{
	if (file)
		fput(file);
}


static int io_sendmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
	struct io_sr_msg *sr = &req->sr_msg;

	if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
		return -EINVAL;

	sr->umsg = u64_to_user_ptr(READ_ONCE(sqe->addr));
	sr->len = READ_ONCE(sqe->len);
	sr->msg_flags = READ_ONCE(sqe->msg_flags) | MSG_NOSIGNAL;
	if (sr->msg_flags & MSG_DONTWAIT)
		req->flags |= REQ_F_NOWAIT;

#ifdef CONFIG_COMPAT
	if (req->ctx->compat)
		sr->msg_flags |= MSG_CMSG_COMPAT;
#endif
	return 0;
}


static int io_sq_thread(void *data)
{
	struct io_sq_data *sqd = data;
	struct io_ring_ctx *ctx;
	unsigned long timeout = 0;
	char buf[TASK_COMM_LEN];
	DEFINE_WAIT(wait);

	snprintf(buf, sizeof(buf), "iou-sqp-%d", sqd->task_pid);
	set_task_comm(current, buf);

	if (sqd->sq_cpu != -1)
		set_cpus_allowed_ptr(current, cpumask_of(sqd->sq_cpu));
	else
		set_cpus_allowed_ptr(current, cpu_online_mask);
	current->flags |= PF_NO_SETAFFINITY;

	mutex_lock(&sqd->lock);
	/* a user may had exited before the thread started */
	io_run_task_work_head(&sqd->park_task_work);

	while (!test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state)) {
		int ret;
		bool cap_entries, sqt_spin, needs_sched;

		if (test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state) ||
		    signal_pending(current)) {
			bool did_sig = false;

			mutex_unlock(&sqd->lock);
			if (signal_pending(current)) {
				struct ksignal ksig;

				did_sig = get_signal(&ksig);
			}
			cond_resched();
			mutex_lock(&sqd->lock);
			io_run_task_work();
			io_run_task_work_head(&sqd->park_task_work);
			if (did_sig)
				break;
			timeout = jiffies + sqd->sq_thread_idle;
			continue;
		}
		sqt_spin = false;
		cap_entries = !list_is_singular(&sqd->ctx_list);
		list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
			const struct cred *creds = NULL;

			if (ctx->sq_creds != current_cred())
				creds = override_creds(ctx->sq_creds);
			ret = __io_sq_thread(ctx, cap_entries);
			if (creds)
				revert_creds(creds);
			if (!sqt_spin && (ret > 0 || !list_empty(&ctx->iopoll_list)))
				sqt_spin = true;
		}

		if (sqt_spin || !time_after(jiffies, timeout)) {
			io_run_task_work();
			cond_resched();
			if (sqt_spin)
				timeout = jiffies + sqd->sq_thread_idle;
			continue;
		}

		prepare_to_wait(&sqd->wait, &wait, TASK_INTERRUPTIBLE);
		if (!test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state)) {
			list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
				io_ring_set_wakeup_flag(ctx);

			needs_sched = true;
			list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
				if ((ctx->flags & IORING_SETUP_IOPOLL) &&
				    !list_empty_careful(&ctx->iopoll_list)) {
					needs_sched = false;
					break;
				}
				if (io_sqring_entries(ctx)) {
					needs_sched = false;
					break;
				}
			}

			if (needs_sched) {
				mutex_unlock(&sqd->lock);
				schedule();
				mutex_lock(&sqd->lock);
			}
			list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
				io_ring_clear_wakeup_flag(ctx);
		}

		finish_wait(&sqd->wait, &wait);
		io_run_task_work_head(&sqd->park_task_work);
		timeout = jiffies + sqd->sq_thread_idle;
	}

	io_uring_cancel_sqpoll(sqd);
	sqd->thread = NULL;
	list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
		io_ring_set_wakeup_flag(ctx);
	io_run_task_work();
	io_run_task_work_head(&sqd->park_task_work);
	mutex_unlock(&sqd->lock);

	complete(&sqd->exited);
	do_exit(0);


static int io_register_files_update(struct io_ring_ctx *ctx, void __user *arg,
				    unsigned nr_args)
{
	struct io_uring_rsrc_update2 up;

	if (!nr_args)
		return -EINVAL;
	memset(&up, 0, sizeof(up));
	if (copy_from_user(&up, arg, sizeof(struct io_uring_rsrc_update)))
		return -EFAULT;
	return __io_register_rsrc_update(ctx, IORING_RSRC_FILE, &up, nr_args);


static inline void io_put_req_deferred(struct io_kiocb *req, int refs)
{
	if (req_ref_sub_and_test(req, refs))
		io_free_req_deferred(req);
}


static struct io_rsrc_node *io_rsrc_node_alloc(struct io_ring_ctx *ctx)
{
	struct io_rsrc_node *ref_node;

	ref_node = kzalloc(sizeof(*ref_node), GFP_KERNEL);
	if (!ref_node)
		return NULL;

	if (percpu_ref_init(&ref_node->refs, io_rsrc_node_ref_zero,
			    0, GFP_KERNEL)) {
		kfree(ref_node);
		return NULL;
	}
	INIT_LIST_HEAD(&ref_node->node);
	INIT_LIST_HEAD(&ref_node->rsrc_list);
	ref_node->done = false;
	return ref_node;