fs/io_uring.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Shared application/kernel submission and completion ring pairs, for
 * supporting fast/efficient IO.
 *
 * A note on the read/write ordering memory barriers that are matched between
 * the application and kernel side.
 *
 * After the application reads the CQ ring tail, it must use an
 * appropriate smp_rmb() to pair with the smp_wmb() the kernel uses
 * before writing the tail (using smp_load_acquire to read the tail will
 * do). It also needs a smp_mb() before updating CQ head (ordering the
 * entry load(s) with the head store), pairing with an implicit barrier
 * through a control-dependency in io_get_cqring (smp_store_release to
 * store head will do). Failure to do so could lead to reading invalid
 * CQ entries.
 *
 * Likewise, the application must use an appropriate smp_wmb() before
 * writing the SQ tail (ordering SQ entry stores with the tail store),
 * which pairs with smp_load_acquire in io_get_sqring (smp_store_release
 * to store the tail will do). And it needs a barrier ordering the SQ
 * head load before writing new SQ entries (smp_load_acquire to read
 * head will do).
 *
 * When using the SQ poll thread (IORING_SETUP_SQPOLL), the application
 * needs to check the SQ flags for IORING_SQ_NEED_WAKEUP *after*
 * updating the SQ tail; a full memory barrier smp_mb() is needed
 * between.
 *
 * Also see the examples in the liburing library:
 *
 *	git://git.kernel.dk/liburing
 *
 * io_uring also uses READ/WRITE_ONCE() for _any_ store or load that happens
 * from data shared between the kernel and application. This is done both
 * for ordering purposes, but also to ensure that once a value is loaded from
 * data that the application could potentially modify, it remains stable.
 *
 * Copyright (C) 2018-2019 Jens Axboe
 * Copyright (c) 2018-2019 Christoph Hellwig
 */
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/syscalls.h>
#include <linux/compat.h>
#include <net/compat.h>
#include <linux/refcount.h>
#include <linux/uio.h>
#include <linux/bits.h>

#include <linux/sched/signal.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/percpu.h>
#include <linux/slab.h>
#include <linux/kthread.h>
#include <linux/blkdev.h>
#include <linux/bvec.h>
#include <linux/net.h>
#include <net/sock.h>
#include <net/af_unix.h>
#include <net/scm.h>
#include <linux/anon_inodes.h>
#include <linux/sched/mm.h>
#include <linux/uaccess.h>
#include <linux/nospec.h>
#include <linux/sizes.h>
#include <linux/hugetlb.h>
#include <linux/highmem.h>
#include <linux/namei.h>
#include <linux/fsnotify.h>
#include <linux/fadvise.h>
#include <linux/eventpoll.h>
#include <linux/fs_struct.h>
#include <linux/splice.h>
#include <linux/task_work.h>
#include <linux/pagemap.h>
#include <linux/io_uring.h>
#include <linux/blk-cgroup.h>
#include <linux/audit.h>

#define CREATE_TRACE_POINTS
#include <trace/events/io_uring.h>

#include <uapi/linux/io_uring.h>

#include "internal.h"
#include "io-wq.h"

#define IORING_MAX_ENTRIES	32768
#define IORING_MAX_CQ_ENTRIES	(2 * IORING_MAX_ENTRIES)

/*
 * Shift of 9 is 512 entries, or exactly one page on 64-bit archs
 */
#define IORING_FILE_TABLE_SHIFT	9
#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)
#define IORING_MAX_RESTRICTIONS	(IORING_RESTRICTION_LAST + \
				 IORING_REGISTER_LAST + IORING_OP_LAST)

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

/*
 * This data is shared with the application through the mmap at offsets
 * IORING_OFF_SQ_RING and IORING_OFF_CQ_RING.
 *
 * The offsets to the member fields are published through struct
 * io_sqring_offsets when calling io_uring_setup.
 */
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;
	size_t		len;
	struct		bio_vec *bvec;
	unsigned int	nr_bvecs;
	unsigned long	acct_pages;
};

struct fixed_file_table {
	struct file		**files;
};

struct fixed_file_ref_node {
	struct percpu_ref		refs;
	struct list_head		node;
	struct list_head		file_list;
	struct fixed_file_data		*file_data;
	struct llist_node		llist;
	bool				done;
};

struct fixed_file_data {
	struct fixed_file_table		*table;
	struct io_ring_ctx		*ctx;

	struct fixed_file_ref_node	*node;
	struct percpu_ref		refs;
	struct completion		done;
	struct list_head		ref_list;
	spinlock_t			lock;
};

struct io_buffer {
	struct list_head list;
	__u64 addr;
	__u32 len;
	__u16 bid;
};

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;
};

struct io_sq_data {
	refcount_t		refs;
	struct mutex		lock;

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

	struct task_struct	*thread;
	struct wait_queue_head	wait;
};

struct io_ring_ctx {
	struct {
		struct percpu_ref	refs;
	} ____cacheline_aligned_in_smp;

	struct {
		unsigned int		flags;
		unsigned int		compat: 1;
		unsigned int		limit_mem: 1;
		unsigned int		cq_overflow_flushed: 1;
		unsigned int		drain_next: 1;
		unsigned int		eventfd_async: 1;
		unsigned int		restricted: 1;
		unsigned int		sqo_dead: 1;

		/*
		 * Ring buffer of indices into array of io_uring_sqe, which is
		 * mmapped by the application using the IORING_OFF_SQES offset.
		 *
		 * This indirection could e.g. be used to assign fixed
		 * io_uring_sqe entries to operations and only submit them to
		 * the queue when needed.
		 *
		 * The kernel modifies neither the indices array nor the entries
		 * array.
		 */
		u32			*sq_array;
		unsigned		cached_sq_head;
		unsigned		sq_entries;
		unsigned		sq_mask;
		unsigned		sq_thread_idle;
		unsigned		cached_sq_dropped;
		unsigned		cached_cq_overflow;
		unsigned long		sq_check_overflow;

		struct list_head	defer_list;
		struct list_head	timeout_list;
		struct list_head	cq_overflow_list;

		struct io_uring_sqe	*sq_sqes;
	} ____cacheline_aligned_in_smp;

	struct io_rings	*rings;

	/* IO offload */
	struct io_wq		*io_wq;

	/*
	 * For SQPOLL usage - we hold a reference to the parent task, so we
	 * have access to the ->files
	 */
	struct task_struct	*sqo_task;

	/* Only used for accounting purposes */
	struct mm_struct	*mm_account;

#ifdef CONFIG_BLK_CGROUP
	struct cgroup_subsys_state	*sqo_blkcg_css;
#endif

	struct io_sq_data	*sq_data;	/* if using sq thread polling */

	struct wait_queue_head	sqo_sq_wait;
	struct wait_queue_entry	sqo_wait_entry;
	struct list_head	sqd_list;

	/*
	 * If used, fixed file set. Writers must ensure that ->refs is dead,
	 * readers must ensure that ->refs is alive as long as the file* is
	 * used. Only updated through io_uring_register(2).
	 */
	struct fixed_file_data	*file_data;
	unsigned		nr_user_files;

	/* if used, fixed mapped user buffers */
	unsigned		nr_user_bufs;
	struct io_mapped_ubuf	*user_bufs;

	struct user_struct	*user;

	const struct cred	*creds;

#ifdef CONFIG_AUDIT
	kuid_t			loginuid;
	unsigned int		sessionid;
#endif

	struct completion	ref_comp;
	struct completion	sq_thread_comp;

	/* if all else fails... */
	struct io_kiocb		*fallback_req;

#if defined(CONFIG_UNIX)
	struct socket		*ring_sock;
#endif

	struct xarray		io_buffers;

	struct xarray		personalities;
	u32			pers_next;

	struct {
		unsigned		cached_cq_tail;
		unsigned		cq_entries;
		unsigned		cq_mask;
		atomic_t		cq_timeouts;
		unsigned		cq_last_tm_flush;
		unsigned long		cq_check_overflow;
		struct wait_queue_head	cq_wait;
		struct fasync_struct	*cq_fasync;
		struct eventfd_ctx	*cq_ev_fd;
	} ____cacheline_aligned_in_smp;

	struct {
		struct mutex		uring_lock;
		wait_queue_head_t	wait;
	} ____cacheline_aligned_in_smp;

	struct {
		spinlock_t		completion_lock;

		/*
		 * ->iopoll_list is protected by the ctx->uring_lock for
		 * io_uring instances that don't use IORING_SETUP_SQPOLL.
		 * For SQPOLL, only the single threaded io_sq_thread() will
		 * manipulate the list, hence no extra locking is needed there.
		 */
		struct list_head	iopoll_list;
		struct hlist_head	*cancel_hash;
		unsigned		cancel_hash_bits;
		bool			poll_multi_file;

		spinlock_t		inflight_lock;
		struct list_head	inflight_list;
	} ____cacheline_aligned_in_smp;

	struct delayed_work		file_put_work;
	struct llist_head		file_put_llist;

	struct work_struct		exit_work;
	struct io_restriction		restrictions;
};

/*
 * First field must be the file pointer in all the
 * iocb unions! See also 'struct kiocb' in <linux/fs.h>
 */
struct io_poll_iocb {
	struct file			*file;
	union {
		struct wait_queue_head	*head;
		u64			addr;
	};
	__poll_t			events;
	bool				done;
	bool				canceled;
	struct wait_queue_entry		wait;
};

struct io_close {
	struct file			*file;
	struct file			*put_file;
	int				fd;
};

struct io_timeout_data {
	struct io_kiocb			*req;
	struct hrtimer			timer;
	struct timespec64		ts;
	enum hrtimer_mode		mode;
};

struct io_accept {
	struct file			*file;
	struct sockaddr __user		*addr;
	int __user			*addr_len;
	int				flags;
	unsigned long			nofile;
};

struct io_sync {
	struct file			*file;
	loff_t				len;
	loff_t				off;
	int				flags;
	int				mode;
};

struct io_cancel {
	struct file			*file;
	u64				addr;
};

struct io_timeout {
	struct file			*file;
	u32				off;
	u32				target_seq;
	struct list_head		list;
};

struct io_timeout_rem {
	struct file			*file;
	u64				addr;
};

struct io_rw {
	/* NOTE: kiocb has the file as the first member, so don't do it here */
	struct kiocb			kiocb;
	u64				addr;
	u64				len;
};

struct io_connect {
	struct file			*file;
	struct sockaddr __user		*addr;
	int				addr_len;
};

struct io_sr_msg {
	struct file			*file;
	union {
		struct user_msghdr __user *umsg;
		void __user		*buf;
	};
	int				msg_flags;
	int				bgid;
	size_t				len;
	struct io_buffer		*kbuf;
};

struct io_open {
	struct file			*file;
	int				dfd;
	bool				ignore_nonblock;
	struct filename			*filename;
	struct open_how			how;
	unsigned long			nofile;
};

struct io_files_update {
	struct file			*file;
	u64				arg;
	u32				nr_args;
	u32				offset;
};

struct io_fadvise {
	struct file			*file;
	u64				offset;
	u32				len;
	u32				advice;
};

struct io_madvise {
	struct file			*file;
	u64				addr;
	u32				len;
	u32				advice;
};

struct io_epoll {
	struct file			*file;
	int				epfd;
	int				op;
	int				fd;
	struct epoll_event		event;
};

struct io_splice {
	struct file			*file_out;
	struct file			*file_in;
	loff_t				off_out;
	loff_t				off_in;
	u64				len;
	unsigned int			flags;
};

struct io_provide_buf {
	struct file			*file;
	__u64				addr;
	__u32				len;
	__u32				bgid;
	__u16				nbufs;
	__u16				bid;
};

struct io_statx {
	struct file			*file;
	int				dfd;
	unsigned int			mask;
	unsigned int			flags;
	const char __user		*filename;
	struct statx __user		*buffer;
};

struct io_completion {
	struct file			*file;
	struct list_head		list;
	u32				cflags;
};

struct io_async_connect {
	struct sockaddr_storage		address;
};

struct io_async_msghdr {
	struct iovec			fast_iov[UIO_FASTIOV];
	struct iovec			*iov;
	struct sockaddr __user		*uaddr;
	struct msghdr			msg;
	struct sockaddr_storage		addr;
};

struct io_async_rw {
	struct iovec			fast_iov[UIO_FASTIOV];
	const struct iovec		*free_iovec;
	struct iov_iter			iter;
	size_t				bytes_done;
	struct wait_page_queue		wpq;
};

enum {
	REQ_F_FIXED_FILE_BIT	= IOSQE_FIXED_FILE_BIT,
	REQ_F_IO_DRAIN_BIT	= IOSQE_IO_DRAIN_BIT,
	REQ_F_LINK_BIT		= IOSQE_IO_LINK_BIT,
	REQ_F_HARDLINK_BIT	= IOSQE_IO_HARDLINK_BIT,
	REQ_F_FORCE_ASYNC_BIT	= IOSQE_ASYNC_BIT,
	REQ_F_BUFFER_SELECT_BIT	= IOSQE_BUFFER_SELECT_BIT,

	REQ_F_LINK_HEAD_BIT,
	REQ_F_FAIL_LINK_BIT,
	REQ_F_INFLIGHT_BIT,
	REQ_F_CUR_POS_BIT,
	REQ_F_NOWAIT_BIT,
	REQ_F_LINK_TIMEOUT_BIT,
	REQ_F_ISREG_BIT,
	REQ_F_NEED_CLEANUP_BIT,
	REQ_F_POLLED_BIT,
	REQ_F_BUFFER_SELECTED_BIT,
	REQ_F_NO_FILE_TABLE_BIT,
	REQ_F_WORK_INITIALIZED_BIT,
	REQ_F_LTIMEOUT_ACTIVE_BIT,

	/* not a real bit, just to check we're not overflowing the space */
	__REQ_F_LAST_BIT,
};

enum {
	/* ctx owns file */
	REQ_F_FIXED_FILE	= BIT(REQ_F_FIXED_FILE_BIT),
	/* drain existing IO first */
	REQ_F_IO_DRAIN		= BIT(REQ_F_IO_DRAIN_BIT),
	/* linked sqes */
	REQ_F_LINK		= BIT(REQ_F_LINK_BIT),
	/* doesn't sever on completion < 0 */
	REQ_F_HARDLINK		= BIT(REQ_F_HARDLINK_BIT),
	/* IOSQE_ASYNC */
	REQ_F_FORCE_ASYNC	= BIT(REQ_F_FORCE_ASYNC_BIT),
	/* IOSQE_BUFFER_SELECT */
	REQ_F_BUFFER_SELECT	= BIT(REQ_F_BUFFER_SELECT_BIT),

	/* head of a link */
	REQ_F_LINK_HEAD		= BIT(REQ_F_LINK_HEAD_BIT),
	/* fail rest of links */
	REQ_F_FAIL_LINK		= BIT(REQ_F_FAIL_LINK_BIT),
	/* on inflight list */
	REQ_F_INFLIGHT		= BIT(REQ_F_INFLIGHT_BIT),
	/* read/write uses file position */
	REQ_F_CUR_POS		= BIT(REQ_F_CUR_POS_BIT),
	/* must not punt to workers */
	REQ_F_NOWAIT		= BIT(REQ_F_NOWAIT_BIT),
	/* has or had linked timeout */
	REQ_F_LINK_TIMEOUT	= BIT(REQ_F_LINK_TIMEOUT_BIT),
	/* regular file */
	REQ_F_ISREG		= BIT(REQ_F_ISREG_BIT),
	/* needs cleanup */
	REQ_F_NEED_CLEANUP	= BIT(REQ_F_NEED_CLEANUP_BIT),
	/* already went through poll handler */
	REQ_F_POLLED		= BIT(REQ_F_POLLED_BIT),
	/* buffer already selected */
	REQ_F_BUFFER_SELECTED	= BIT(REQ_F_BUFFER_SELECTED_BIT),
	/* doesn't need file table for this request */
	REQ_F_NO_FILE_TABLE	= BIT(REQ_F_NO_FILE_TABLE_BIT),
	/* io_wq_work is initialized */
	REQ_F_WORK_INITIALIZED	= BIT(REQ_F_WORK_INITIALIZED_BIT),
	/* linked timeout is active, i.e. prepared by link's head */
	REQ_F_LTIMEOUT_ACTIVE	= BIT(REQ_F_LTIMEOUT_ACTIVE_BIT),
};

struct async_poll {
	struct io_poll_iocb	poll;
	struct io_poll_iocb	*double_poll;
};

/*
 * NOTE! Each of the iocb union members has the file pointer
 * as the first entry in their struct definition. So you can
 * access the file pointer through any of the sub-structs,
 * or directly as just 'ki_filp' in this struct.
 */
struct io_kiocb {
	union {
		struct file		*file;
		struct io_rw		rw;
		struct io_poll_iocb	poll;
		struct io_accept	accept;
		struct io_sync		sync;
		struct io_cancel	cancel;
		struct io_timeout	timeout;
		struct io_timeout_rem	timeout_rem;
		struct io_connect	connect;
		struct io_sr_msg	sr_msg;
		struct io_open		open;
		struct io_close		close;
		struct io_files_update	files_update;
		struct io_fadvise	fadvise;
		struct io_madvise	madvise;
		struct io_epoll		epoll;
		struct io_splice	splice;
		struct io_provide_buf	pbuf;
		struct io_statx		statx;
		/* use only after cleaning per-op data, see io_clean_op() */
		struct io_completion	compl;
	};

	/* opcode allocated if it needs to store data for async defer */
	void				*async_data;
	u8				opcode;
	/* polled IO has completed */
	u8				iopoll_completed;

	u16				buf_index;
	u32				result;

	struct io_ring_ctx		*ctx;
	unsigned int			flags;
	refcount_t			refs;
	struct task_struct		*task;
	u64				user_data;

	struct list_head		link_list;

	/*
	 * 1. used with ctx->iopoll_list with reads/writes
	 * 2. to track reqs with ->files (see io_op_def::file_table)
	 */
	struct list_head		inflight_entry;

	struct percpu_ref		*fixed_file_refs;
	struct callback_head		task_work;
	/* for polled requests, i.e. IORING_OP_POLL_ADD and async armed poll */
	struct hlist_node		hash_node;
	struct async_poll		*apoll;
	struct io_wq_work		work;
};

struct io_defer_entry {
	struct list_head	list;
	struct io_kiocb		*req;
	u32			seq;
};

#define IO_IOPOLL_BATCH			8

struct io_comp_state {
	unsigned int		nr;
	struct list_head	list;
	struct io_ring_ctx	*ctx;
};

struct io_submit_state {
	struct blk_plug		plug;

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

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

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

struct io_op_def {
	/* needs req->file assigned */
	unsigned		needs_file : 1;
	/* don't fail if file grab fails */
	unsigned		needs_file_no_error : 1;
	/* hash wq insertion if file is a regular file */
	unsigned		hash_reg_file : 1;
	/* unbound wq insertion if file is a non-regular file */
	unsigned		unbound_nonreg_file : 1;
	/* opcode is not supported by this kernel */
	unsigned		not_supported : 1;
	/* set if opcode supports polled "wait" */
	unsigned		pollin : 1;
	unsigned		pollout : 1;
	/* op supports buffer selection */
	unsigned		buffer_select : 1;
	/* must always have async data allocated */
	unsigned		needs_async_data : 1;
	/* size of async data needed, if any */
	unsigned short		async_size;
	unsigned		work_flags;
};

static const struct io_op_def io_op_defs[] = {
	[IORING_OP_NOP] = {},
	[IORING_OP_READV] = {
		.needs_file		= 1,
		.unbound_nonreg_file	= 1,
		.pollin			= 1,
		.buffer_select		= 1,
		.needs_async_data	= 1,
		.async_size		= sizeof(struct io_async_rw),
		.work_flags		= IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG,
	},
	[IORING_OP_WRITEV] = {
		.needs_file		= 1,
		.hash_reg_file		= 1,
		.unbound_nonreg_file	= 1,
		.pollout		= 1,
		.needs_async_data	= 1,
		.async_size		= sizeof(struct io_async_rw),
		.work_flags		= IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG |
						IO_WQ_WORK_FSIZE,
	},
	[IORING_OP_FSYNC] = {
		.needs_file		= 1,
		.work_flags		= IO_WQ_WORK_BLKCG,
	},
	[IORING_OP_READ_FIXED] = {
		.needs_file		= 1,
		.unbound_nonreg_file	= 1,
		.pollin			= 1,
		.async_size		= sizeof(struct io_async_rw),
		.work_flags		= IO_WQ_WORK_BLKCG | IO_WQ_WORK_MM,
	},
	[IORING_OP_WRITE_FIXED] = {
		.needs_file		= 1,
		.hash_reg_file		= 1,
		.unbound_nonreg_file	= 1,
		.pollout		= 1,
		.async_size		= sizeof(struct io_async_rw),
		.work_flags		= IO_WQ_WORK_BLKCG | IO_WQ_WORK_FSIZE |
						IO_WQ_WORK_MM,
	},
	[IORING_OP_POLL_ADD] = {
		.needs_file		= 1,
		.unbound_nonreg_file	= 1,
	},
	[IORING_OP_POLL_REMOVE] = {},
	[IORING_OP_SYNC_FILE_RANGE] = {
		.needs_file		= 1,
		.work_flags		= IO_WQ_WORK_BLKCG,
	},
	[IORING_OP_SENDMSG] = {
		.needs_file		= 1,
		.unbound_nonreg_file	= 1,
		.pollout		= 1,
		.needs_async_data	= 1,
		.async_size		= sizeof(struct io_async_msghdr),
		.work_flags		= IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG |
						IO_WQ_WORK_FS,
	},
	[IORING_OP_RECVMSG] = {
		.needs_file		= 1,
		.unbound_nonreg_file	= 1,
		.pollin			= 1,
		.buffer_select		= 1,
		.needs_async_data	= 1,
		.async_size		= sizeof(struct io_async_msghdr),
		.work_flags		= IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG |
						IO_WQ_WORK_FS,
	},
	[IORING_OP_TIMEOUT] = {
		.needs_async_data	= 1,
		.async_size		= sizeof(struct io_timeout_data),
		.work_flags		= IO_WQ_WORK_MM,
	},
	[IORING_OP_TIMEOUT_REMOVE] = {},
	[IORING_OP_ACCEPT] = {
		.needs_file		= 1,
		.unbound_nonreg_file	= 1,
		.pollin			= 1,
		.work_flags		= IO_WQ_WORK_MM | IO_WQ_WORK_FILES,
	},
	[IORING_OP_ASYNC_CANCEL] = {},
	[IORING_OP_LINK_TIMEOUT] = {
		.needs_async_data	= 1,
		.async_size		= sizeof(struct io_timeout_data),
		.work_flags		= IO_WQ_WORK_MM,
	},
	[IORING_OP_CONNECT] = {
		.needs_file		= 1,
		.unbound_nonreg_file	= 1,
		.pollout		= 1,
		.needs_async_data	= 1,
		.async_size		= sizeof(struct io_async_connect),
		.work_flags		= IO_WQ_WORK_MM,
	},
	[IORING_OP_FALLOCATE] = {
		.needs_file		= 1,
		.work_flags		= IO_WQ_WORK_BLKCG | IO_WQ_WORK_FSIZE,
	},
	[IORING_OP_OPENAT] = {
		.work_flags		= IO_WQ_WORK_FILES | IO_WQ_WORK_BLKCG |
						IO_WQ_WORK_FS,
	},
	[IORING_OP_CLOSE] = {
		.needs_file		= 1,
		.needs_file_no_error	= 1,
		.work_flags		= IO_WQ_WORK_FILES | IO_WQ_WORK_BLKCG,
	},
	[IORING_OP_FILES_UPDATE] = {
		.work_flags		= IO_WQ_WORK_FILES | IO_WQ_WORK_MM,
	},
	[IORING_OP_STATX] = {
		.work_flags		= IO_WQ_WORK_FILES | IO_WQ_WORK_MM |
						IO_WQ_WORK_FS | IO_WQ_WORK_BLKCG,
	},
	[IORING_OP_READ] = {
		.needs_file		= 1,
		.unbound_nonreg_file	= 1,
		.pollin			= 1,
		.buffer_select		= 1,
		.async_size		= sizeof(struct io_async_rw),
		.work_flags		= IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG,
	},
	[IORING_OP_WRITE] = {
		.needs_file		= 1,
		.hash_reg_file		= 1,
		.unbound_nonreg_file	= 1,
		.pollout		= 1,
		.async_size		= sizeof(struct io_async_rw),
		.work_flags		= IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG |
						IO_WQ_WORK_FSIZE,
	},
	[IORING_OP_FADVISE] = {
		.needs_file		= 1,
		.work_flags		= IO_WQ_WORK_BLKCG,
	},
	[IORING_OP_MADVISE] = {
		.work_flags		= IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG,
	},
	[IORING_OP_SEND] = {
		.needs_file		= 1,
		.unbound_nonreg_file	= 1,
		.pollout		= 1,
		.work_flags		= IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG,
	},
	[IORING_OP_RECV] = {
		.needs_file		= 1,
		.unbound_nonreg_file	= 1,
		.pollin			= 1,
		.buffer_select		= 1,
		.work_flags		= IO_WQ_WORK_MM | IO_WQ_WORK_BLKCG,
	},
	[IORING_OP_OPENAT2] = {
		.work_flags		= IO_WQ_WORK_FILES | IO_WQ_WORK_FS |
						IO_WQ_WORK_BLKCG,
	},
	[IORING_OP_EPOLL_CTL] = {
		.unbound_nonreg_file	= 1,
		.work_flags		= IO_WQ_WORK_FILES,
	},
	[IORING_OP_SPLICE] = {
		.needs_file		= 1,
		.hash_reg_file		= 1,
		.unbound_nonreg_file	= 1,
		.work_flags		= IO_WQ_WORK_BLKCG,
	},
	[IORING_OP_PROVIDE_BUFFERS] = {},
	[IORING_OP_REMOVE_BUFFERS] = {},
	[IORING_OP_TEE] = {
		.needs_file		= 1,
		.hash_reg_file		= 1,
		.unbound_nonreg_file	= 1,
	},
};

enum io_mem_account {
	ACCT_LOCKED,
	ACCT_PINNED,
};

static void destroy_fixed_file_ref_node(struct fixed_file_ref_node *ref_node);
static struct fixed_file_ref_node *alloc_fixed_file_ref_node(
			struct io_ring_ctx *ctx);

static void __io_complete_rw(struct io_kiocb *req, long res, long res2,
			     struct io_comp_state *cs);
static void io_cqring_fill_event(struct io_kiocb *req, long res);
static void io_put_req(struct io_kiocb *req);
static void io_put_req_deferred(struct io_kiocb *req, int nr);
static void io_double_put_req(struct io_kiocb *req);
static struct io_kiocb *io_prep_linked_timeout(struct io_kiocb *req);
static void __io_queue_linked_timeout(struct io_kiocb *req);
static void io_queue_linked_timeout(struct io_kiocb *req);
static int __io_sqe_files_update(struct io_ring_ctx *ctx,
				 struct io_uring_files_update *ip,
				 unsigned nr_args);
static void __io_clean_op(struct io_kiocb *req);
static struct file *io_file_get(struct io_submit_state *state,
				struct io_kiocb *req, int fd, bool fixed);
static void __io_queue_sqe(struct io_kiocb *req, struct io_comp_state *cs);
static void io_file_put_work(struct work_struct *work);

static ssize_t io_import_iovec(int rw, struct io_kiocb *req,
			       struct iovec **iovec, struct iov_iter *iter,
			       bool needs_lock);
static int io_setup_async_rw(struct io_kiocb *req, const struct iovec *iovec,
			     const struct iovec *fast_iov,
			     struct iov_iter *iter, bool force);
static void io_req_drop_files(struct io_kiocb *req);
static void io_req_task_queue(struct io_kiocb *req);

static struct kmem_cache *req_cachep;

static const struct file_operations io_uring_fops;

struct sock *io_uring_get_socket(struct file *file)
{
#if defined(CONFIG_UNIX)
	if (file->f_op == &io_uring_fops) {
		struct io_ring_ctx *ctx = file->private_data;

		return ctx->ring_sock->sk;
	}
#endif
	return NULL;
}
EXPORT_SYMBOL(io_uring_get_socket);

static inline void io_clean_op(struct io_kiocb *req)
{
	if (req->flags & (REQ_F_NEED_CLEANUP | REQ_F_BUFFER_SELECTED))
		__io_clean_op(req);
}

static inline bool __io_match_files(struct io_kiocb *req,
				    struct files_struct *files)
{
	if (req->file && req->file->f_op == &io_uring_fops)
		return true;

	return ((req->flags & REQ_F_WORK_INITIALIZED) &&
	        (req->work.flags & IO_WQ_WORK_FILES)) &&
		req->work.identity->files == files;
}

static void io_refs_resurrect(struct percpu_ref *ref, struct completion *compl)
{
	bool got = percpu_ref_tryget(ref);

	/* already at zero, wait for ->release() */
	if (!got)
		wait_for_completion(compl);
	percpu_ref_resurrect(ref);
	if (got)
		percpu_ref_put(ref);
}

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

	if (task && head->task != task) {
		/* in terms of cancelation, always match if req task is dead */
		if (head->task->flags & PF_EXITING)
			return true;
		return false;
	}
	if (!files)
		return true;
	if (__io_match_files(head, files))
		return true;
	if (head->flags & REQ_F_LINK_HEAD) {
		list_for_each_entry(link, &head->link_list, link_list) {
			if (__io_match_files(link, files))
				return true;
		}
	}
	return false;
}


static void io_sq_thread_drop_mm(void)
{
	struct mm_struct *mm = current->mm;

	if (mm) {
		kthread_unuse_mm(mm);
		mmput(mm);
		current->mm = NULL;
	}
}

static int __io_sq_thread_acquire_mm(struct io_ring_ctx *ctx)
{
	struct mm_struct *mm;

	if (current->flags & PF_EXITING)
		return -EFAULT;
	if (current->mm)
		return 0;

	/* Should never happen */
	if (unlikely(!(ctx->flags & IORING_SETUP_SQPOLL)))
		return -EFAULT;

	task_lock(ctx->sqo_task);
	mm = ctx->sqo_task->mm;
	if (unlikely(!mm || !mmget_not_zero(mm)))
		mm = NULL;
	task_unlock(ctx->sqo_task);

	if (mm) {
		kthread_use_mm(mm);
		return 0;
	}

	return -EFAULT;
}

static int io_sq_thread_acquire_mm(struct io_ring_ctx *ctx,
				   struct io_kiocb *req)
{
	if (!(io_op_defs[req->opcode].work_flags & IO_WQ_WORK_MM))
		return 0;
	return __io_sq_thread_acquire_mm(ctx);
}

static void io_sq_thread_associate_blkcg(struct io_ring_ctx *ctx,
					 struct cgroup_subsys_state **cur_css)

{
#ifdef CONFIG_BLK_CGROUP
	/* puts the old one when swapping */
	if (*cur_css != ctx->sqo_blkcg_css) {
		kthread_associate_blkcg(ctx->sqo_blkcg_css);
		*cur_css = ctx->sqo_blkcg_css;
	}
#endif
}

static void io_sq_thread_unassociate_blkcg(void)
{
#ifdef CONFIG_BLK_CGROUP
	kthread_associate_blkcg(NULL);
#endif
}

static inline void req_set_fail_links(struct io_kiocb *req)
{
	if ((req->flags & (REQ_F_LINK | REQ_F_HARDLINK)) == REQ_F_LINK)
		req->flags |= REQ_F_FAIL_LINK;
}

/*
 * None of these are dereferenced, they are simply used to check if any of
 * them have changed. If we're under current and check they are still the
 * same, we're fine to grab references to them for actual out-of-line use.
 */
static void io_init_identity(struct io_identity *id)
{
	id->files = current->files;
	id->mm = current->mm;
#ifdef CONFIG_BLK_CGROUP
	rcu_read_lock();
	id->blkcg_css = blkcg_css();
	rcu_read_unlock();
#endif
	id->creds = current_cred();
	id->nsproxy = current->nsproxy;
	id->fs = current->fs;
	id->fsize = rlimit(RLIMIT_FSIZE);
#ifdef CONFIG_AUDIT
	id->loginuid = current->loginuid;
	id->sessionid = current->sessionid;
#endif
	refcount_set(&id->count, 1);
}

static inline void __io_req_init_async(struct io_kiocb *req)
{
	memset(&req->work, 0, sizeof(req->work));
	req->flags |= REQ_F_WORK_INITIALIZED;
}

/*
 * Note: must call io_req_init_async() for the first time you
 * touch any members of io_wq_work.
 */
static inline void io_req_init_async(struct io_kiocb *req)
{
	struct io_uring_task *tctx = current->io_uring;

	if (req->flags & REQ_F_WORK_INITIALIZED)
		return;

	__io_req_init_async(req);

	/* Grab a ref if this isn't our static identity */
	req->work.identity = tctx->identity;
	if (tctx->identity != &tctx->__identity)
		refcount_inc(&req->work.identity->count);
}

static inline bool io_async_submit(struct io_ring_ctx *ctx)
{
	return ctx->flags & IORING_SETUP_SQPOLL;
}

static void io_ring_ctx_ref_free(struct percpu_ref *ref)
{
	struct io_ring_ctx *ctx = container_of(ref, struct io_ring_ctx, refs);

	complete(&ctx->ref_comp);
}

static inline bool io_is_timeout_noseq(struct io_kiocb *req)
{
	return !req->timeout.off;
}

static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
{
	struct io_ring_ctx *ctx;
	int hash_bits;

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

	ctx->fallback_req = kmem_cache_alloc(req_cachep, GFP_KERNEL);
	if (!ctx->fallback_req)
		goto err;

	/*
	 * Use 5 bits less than the max cq entries, that should give us around
	 * 32 entries per hash list if totally full and uniformly spread.
	 */
	hash_bits = ilog2(p->cq_entries);
	hash_bits -= 5;
	if (hash_bits <= 0)
		hash_bits = 1;
	ctx->cancel_hash_bits = hash_bits;
	ctx->cancel_hash = kmalloc((1U << hash_bits) * sizeof(struct hlist_head),
					GFP_KERNEL);
	if (!ctx->cancel_hash)
		goto err;
	__hash_init(ctx->cancel_hash, 1U << hash_bits);

	if (percpu_ref_init(&ctx->refs, io_ring_ctx_ref_free,
			    PERCPU_REF_ALLOW_REINIT, GFP_KERNEL))
		goto err;

	ctx->flags = p->flags;
	init_waitqueue_head(&ctx->sqo_sq_wait);
	INIT_LIST_HEAD(&ctx->sqd_list);
	init_waitqueue_head(&ctx->cq_wait);
	INIT_LIST_HEAD(&ctx->cq_overflow_list);
	init_completion(&ctx->ref_comp);
	init_completion(&ctx->sq_thread_comp);
	xa_init_flags(&ctx->io_buffers, XA_FLAGS_ALLOC1);
	xa_init_flags(&ctx->personalities, XA_FLAGS_ALLOC1);
	mutex_init(&ctx->uring_lock);
	init_waitqueue_head(&ctx->wait);
	spin_lock_init(&ctx->completion_lock);
	INIT_LIST_HEAD(&ctx->iopoll_list);
	INIT_LIST_HEAD(&ctx->defer_list);
	INIT_LIST_HEAD(&ctx->timeout_list);
	spin_lock_init(&ctx->inflight_lock);
	INIT_LIST_HEAD(&ctx->inflight_list);
	INIT_DELAYED_WORK(&ctx->file_put_work, io_file_put_work);
	init_llist_head(&ctx->file_put_llist);
	return ctx;
err:
	if (ctx->fallback_req)
		kmem_cache_free(req_cachep, ctx->fallback_req);
	kfree(ctx->cancel_hash);
	kfree(ctx);
	return 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->cached_cq_tail
				+ READ_ONCE(ctx->cached_cq_overflow);
	}

	return false;
}

static void __io_commit_cqring(struct io_ring_ctx *ctx)
{
	struct io_rings *rings = ctx->rings;

	/* order cqe stores with ring update */
	smp_store_release(&rings->cq.tail, ctx->cached_cq_tail);
}

static void io_put_identity(struct io_uring_task *tctx, struct io_kiocb *req)
{
	if (req->work.identity == &tctx->__identity)
		return;
	if (refcount_dec_and_test(&req->work.identity->count))
		kfree(req->work.identity);
}

static void io_req_clean_work(struct io_kiocb *req)
{
	if (!(req->flags & REQ_F_WORK_INITIALIZED))
		return;

	req->flags &= ~REQ_F_WORK_INITIALIZED;

	if (req->work.flags & IO_WQ_WORK_MM) {
		mmdrop(req->work.identity->mm);
		req->work.flags &= ~IO_WQ_WORK_MM;
	}
#ifdef CONFIG_BLK_CGROUP
	if (req->work.flags & IO_WQ_WORK_BLKCG) {
		css_put(req->work.identity->blkcg_css);
		req->work.flags &= ~IO_WQ_WORK_BLKCG;
	}
#endif
	if (req->work.flags & IO_WQ_WORK_CREDS) {
		put_cred(req->work.identity->creds);
		req->work.flags &= ~IO_WQ_WORK_CREDS;
	}
	if (req->work.flags & IO_WQ_WORK_FS) {
		struct fs_struct *fs = req->work.identity->fs;

		spin_lock(&req->work.identity->fs->lock);
		if (--fs->users)
			fs = NULL;
		spin_unlock(&req->work.identity->fs->lock);
		if (fs)
			free_fs_struct(fs);
		req->work.flags &= ~IO_WQ_WORK_FS;
	}
	if (req->flags & REQ_F_INFLIGHT)
		io_req_drop_files(req);

	io_put_identity(req->task->io_uring, req);
}

/*
 * Create a private copy of io_identity, since some fields don't match
 * the current context.
 */
static bool io_identity_cow(struct io_kiocb *req)
{
	struct io_uring_task *tctx = current->io_uring;
	const struct cred *creds = NULL;
	struct io_identity *id;

	if (req->work.flags & IO_WQ_WORK_CREDS)
		creds = req->work.identity->creds;

	id = kmemdup(req->work.identity, sizeof(*id), GFP_KERNEL);
	if (unlikely(!id)) {
		req->work.flags |= IO_WQ_WORK_CANCEL;
		return false;
	}

	/*
	 * We can safely just re-init the creds we copied  Either the field
	 * matches the current one, or we haven't grabbed it yet. The only
	 * exception is ->creds, through registered personalities, so handle
	 * that one separately.
	 */
	io_init_identity(id);
	if (creds)
		id->creds = creds;

	/* add one for this request */
	refcount_inc(&id->count);

	/* drop tctx and req identity references, if needed */
	if (tctx->identity != &tctx->__identity &&
	    refcount_dec_and_test(&tctx->identity->count))
		kfree(tctx->identity);
	if (req->work.identity != &tctx->__identity &&
	    refcount_dec_and_test(&req->work.identity->count))
		kfree(req->work.identity);

	req->work.identity = id;
	tctx->identity = id;
	return true;
}

static bool io_grab_identity(struct io_kiocb *req)
{
	const struct io_op_def *def = &io_op_defs[req->opcode];
	struct io_identity *id = req->work.identity;
	struct io_ring_ctx *ctx = req->ctx;

	if (def->work_flags & IO_WQ_WORK_FSIZE) {
		if (id->fsize != rlimit(RLIMIT_FSIZE))
			return false;
		req->work.flags |= IO_WQ_WORK_FSIZE;
	}
#ifdef CONFIG_BLK_CGROUP
	if (!(req->work.flags & IO_WQ_WORK_BLKCG) &&
	    (def->work_flags & IO_WQ_WORK_BLKCG)) {
		rcu_read_lock();
		if (id->blkcg_css != blkcg_css()) {
			rcu_read_unlock();
			return false;
		}
		/*
		 * This should be rare, either the cgroup is dying or the task
		 * is moving cgroups. Just punt to root for the handful of ios.
		 */
		if (css_tryget_online(id->blkcg_css))
			req->work.flags |= IO_WQ_WORK_BLKCG;
		rcu_read_unlock();
	}
#endif
	if (!(req->work.flags & IO_WQ_WORK_CREDS)) {
		if (id->creds != current_cred())
			return false;
		get_cred(id->creds);
		req->work.flags |= IO_WQ_WORK_CREDS;
	}
#ifdef CONFIG_AUDIT
	if (!uid_eq(current->loginuid, id->loginuid) ||
	    current->sessionid != id->sessionid)
		return false;
#endif
	if (!(req->work.flags & IO_WQ_WORK_FS) &&
	    (def->work_flags & IO_WQ_WORK_FS)) {
		if (current->fs != id->fs)
			return false;
		spin_lock(&id->fs->lock);
		if (!id->fs->in_exec) {
			id->fs->users++;
			req->work.flags |= IO_WQ_WORK_FS;
		} else {
			req->work.flags |= IO_WQ_WORK_CANCEL;
		}
		spin_unlock(&current->fs->lock);
	}
	if (!(req->work.flags & IO_WQ_WORK_FILES) &&
	    (def->work_flags & IO_WQ_WORK_FILES) &&
	    !(req->flags & REQ_F_NO_FILE_TABLE)) {
		if (id->files != current->files ||
		    id->nsproxy != current->nsproxy)
			return false;
		atomic_inc(&id->files->count);
		get_nsproxy(id->nsproxy);

		if (!(req->flags & REQ_F_INFLIGHT)) {
			req->flags |= REQ_F_INFLIGHT;

			spin_lock_irq(&ctx->inflight_lock);
			list_add(&req->inflight_entry, &ctx->inflight_list);
			spin_unlock_irq(&ctx->inflight_lock);
		}
		req->work.flags |= IO_WQ_WORK_FILES;
	}
	if (!(req->work.flags & IO_WQ_WORK_MM) &&
	    (def->work_flags & IO_WQ_WORK_MM)) {
		if (id->mm != current->mm)
			return false;
		mmgrab(id->mm);
		req->work.flags |= IO_WQ_WORK_MM;
	}

	return true;
}

static void io_prep_async_work(struct io_kiocb *req)
{
	const struct io_op_def *def = &io_op_defs[req->opcode];
	struct io_ring_ctx *ctx = req->ctx;
	struct io_identity *id;

	io_req_init_async(req);
	id = req->work.identity;

	if (req->flags & REQ_F_FORCE_ASYNC)
		req->work.flags |= IO_WQ_WORK_CONCURRENT;

	if (req->flags & REQ_F_ISREG) {
		if (def->hash_reg_file || (ctx->flags & IORING_SETUP_IOPOLL))
			io_wq_hash_work(&req->work, file_inode(req->file));
	} else if (!req->file || !S_ISBLK(file_inode(req->file)->i_mode)) {
		if (def->unbound_nonreg_file)
			req->work.flags |= IO_WQ_WORK_UNBOUND;
	}

	/* if we fail grabbing identity, we must COW, regrab, and retry */
	if (io_grab_identity(req))
		return;

	if (!io_identity_cow(req))
		return;

	/* can't fail at this point */
	if (!io_grab_identity(req))
		WARN_ON(1);
}

static void io_prep_async_link(struct io_kiocb *req)
{
	struct io_kiocb *cur;

	io_prep_async_work(req);
	if (req->flags & REQ_F_LINK_HEAD)
		list_for_each_entry(cur, &req->link_list, link_list)
			io_prep_async_work(cur);
}

static struct io_kiocb *__io_queue_async_work(struct io_kiocb *req)
{
	struct io_ring_ctx *ctx = req->ctx;
	struct io_kiocb *link = io_prep_linked_timeout(req);

	trace_io_uring_queue_async_work(ctx, io_wq_is_hashed(&req->work), req,
					&req->work, req->flags);
	io_wq_enqueue(ctx->io_wq, &req->work);
	return link;
}

static void io_queue_async_work(struct io_kiocb *req)
{
	struct io_kiocb *link;

	/* init ->work of the whole link before punting */
	io_prep_async_link(req);
	link = __io_queue_async_work(req);

	if (link)
		io_queue_linked_timeout(link);
}

static void io_kill_timeout(struct io_kiocb *req, int status)
{
	struct io_timeout_data *io = req->async_data;
	int ret;

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

/*
 * 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++;
		}
	}
	spin_unlock_irq(&ctx->completion_lock);
	return canceled != 0;
}

static void __io_queue_deferred(struct io_ring_ctx *ctx)
{
	do {
		struct io_defer_entry *de = list_first_entry(&ctx->defer_list,
						struct io_defer_entry, list);

		if (req_need_defer(de->req, de->seq))
			break;
		list_del_init(&de->list);
		io_req_task_queue(de->req);
		kfree(de);
	} while (!list_empty(&ctx->defer_list));
}

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 void io_commit_cqring(struct io_ring_ctx *ctx)
{
	io_flush_timeouts(ctx);
	__io_commit_cqring(ctx);

	if (unlikely(!list_empty(&ctx->defer_list)))
		__io_queue_deferred(ctx);
}

static inline bool io_sqring_full(struct io_ring_ctx *ctx)
{
	struct io_rings *r = ctx->rings;

	return READ_ONCE(r->sq.tail) - ctx->cached_sq_head == r->sq_ring_entries;
}

static struct io_uring_cqe *io_get_cqring(struct io_ring_ctx *ctx)
{
	struct io_rings *rings = ctx->rings;
	unsigned tail;

	tail = ctx->cached_cq_tail;
	/*
	 * writes to the cq entry need to come after reading head; the
	 * control dependency is enough as we're using WRITE_ONCE to
	 * fill the cq entry
	 */
	if (tail - READ_ONCE(rings->cq.head) == rings->cq_ring_entries)
		return NULL;

	ctx->cached_cq_tail++;
	return &rings->cqes[tail & ctx->cq_mask];
}

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

static void io_cqring_ev_posted(struct io_ring_ctx *ctx)
{
	if (wq_has_sleeper(&ctx->cq_wait)) {
		wake_up_interruptible(&ctx->cq_wait);
		kill_fasync(&ctx->cq_fasync, SIGIO, POLL_IN);
	}
	if (waitqueue_active(&ctx->wait))
		wake_up(&ctx->wait);
	if (ctx->sq_data && waitqueue_active(&ctx->sq_data->wait))
		wake_up(&ctx->sq_data->wait);
	if (io_should_trigger_evfd(ctx))
		eventfd_signal(ctx->cq_ev_fd, 1);
}

static void io_cqring_mark_overflow(struct io_ring_ctx *ctx)
{
	if (list_empty(&ctx->cq_overflow_list)) {
		clear_bit(0, &ctx->sq_check_overflow);
		clear_bit(0, &ctx->cq_check_overflow);
		ctx->rings->sq_flags &= ~IORING_SQ_CQ_OVERFLOW;
	}
}

/* Returns true if there are no backlogged entries after the flush */
static bool __io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force,
				       struct task_struct *tsk,
				       struct files_struct *files)
{
	struct io_rings *rings = ctx->rings;
	struct io_kiocb *req, *tmp;
	struct io_uring_cqe *cqe;
	unsigned long flags;
	LIST_HEAD(list);

	if (!force) {
		if ((ctx->cached_cq_tail - READ_ONCE(rings->cq.head) ==
		    rings->cq_ring_entries))
			return false;
	}

	spin_lock_irqsave(&ctx->completion_lock, flags);

	cqe = NULL;
	list_for_each_entry_safe(req, tmp, &ctx->cq_overflow_list, compl.list) {
		if (!io_match_task(req, tsk, files))
			continue;

		cqe = io_get_cqring(ctx);
		if (!cqe && !force)
			break;

		list_move(&req->compl.list, &list);
		if (cqe) {
			WRITE_ONCE(cqe->user_data, req->user_data);
			WRITE_ONCE(cqe->res, req->result);
			WRITE_ONCE(cqe->flags, req->compl.cflags);
		} else {
			ctx->cached_cq_overflow++;
			WRITE_ONCE(ctx->rings->cq_overflow,
				   ctx->cached_cq_overflow);
		}
	}

	io_commit_cqring(ctx);
	io_cqring_mark_overflow(ctx);

	spin_unlock_irqrestore(&ctx->completion_lock, flags);
	io_cqring_ev_posted(ctx);

	while (!list_empty(&list)) {
		req = list_first_entry(&list, struct io_kiocb, compl.list);
		list_del(&req->compl.list);
		io_put_req(req);
	}

	return cqe != NULL;
}

static void io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force,
				     struct task_struct *tsk,
				     struct files_struct *files)
{
	if (test_bit(0, &ctx->cq_check_overflow)) {
		/* iopoll syncs against uring_lock, not completion_lock */
		if (ctx->flags & IORING_SETUP_IOPOLL)
			mutex_lock(&ctx->uring_lock);
		__io_cqring_overflow_flush(ctx, force, tsk, files);
		if (ctx->flags & IORING_SETUP_IOPOLL)
			mutex_unlock(&ctx->uring_lock);
	}
}

static void __io_cqring_fill_event(struct io_kiocb *req, long res,
				   unsigned int cflags)
{
	struct io_ring_ctx *ctx = req->ctx;
	struct io_uring_cqe *cqe;

	trace_io_uring_complete(ctx, req->user_data, res);

	/*
	 * If we can't get a cq entry, userspace overflowed the
	 * submission (by quite a lot). Increment the overflow count in
	 * the ring.
	 */
	cqe = io_get_cqring(ctx);
	if (likely(cqe)) {
		WRITE_ONCE(cqe->user_data, req->user_data);
		WRITE_ONCE(cqe->res, res);
		WRITE_ONCE(cqe->flags, cflags);
	} else if (ctx->cq_overflow_flushed ||
		   atomic_read(&req->task->io_uring->in_idle)) {
		/*
		 * If we're in ring overflow flush mode, or in task cancel mode,
		 * then we cannot store the request for later flushing, we need
		 * to drop it on the floor.
		 */
		ctx->cached_cq_overflow++;
		WRITE_ONCE(ctx->rings->cq_overflow, ctx->cached_cq_overflow);
	} else {
		if (list_empty(&ctx->cq_overflow_list)) {
			set_bit(0, &ctx->sq_check_overflow);
			set_bit(0, &ctx->cq_check_overflow);
			ctx->rings->sq_flags |= IORING_SQ_CQ_OVERFLOW;
		}
		io_clean_op(req);
		req->result = res;
		req->compl.cflags = cflags;
		refcount_inc(&req->refs);
		list_add_tail(&req->compl.list, &ctx->cq_overflow_list);
	}
}

static void io_cqring_fill_event(struct io_kiocb *req, long res)
{
	__io_cqring_fill_event(req, res, 0);
}

static void io_cqring_add_event(struct io_kiocb *req, long res, long cflags)
{
	struct io_ring_ctx *ctx = req->ctx;
	unsigned long flags;

	spin_lock_irqsave(&ctx->completion_lock, flags);
	__io_cqring_fill_event(req, res, cflags);
	io_commit_cqring(ctx);
	spin_unlock_irqrestore(&ctx->completion_lock, flags);

	io_cqring_ev_posted(ctx);
}

static void io_submit_flush_completions(struct io_comp_state *cs)
{
	struct io_ring_ctx *ctx = cs->ctx;

	spin_lock_irq(&ctx->completion_lock);
	while (!list_empty(&cs->list)) {
		struct io_kiocb *req;

		req = list_first_entry(&cs->list, struct io_kiocb, compl.list);
		list_del(&req->compl.list);
		__io_cqring_fill_event(req, req->result, req->compl.cflags);

		/*
		 * io_free_req() doesn't care about completion_lock unless one
		 * of these flags is set. REQ_F_WORK_INITIALIZED is in the list
		 * because of a potential deadlock with req->work.fs->lock
		 */
		if (req->flags & (REQ_F_FAIL_LINK|REQ_F_LINK_TIMEOUT
				 |REQ_F_WORK_INITIALIZED)) {
			spin_unlock_irq(&ctx->completion_lock);
			io_put_req(req);
			spin_lock_irq(&ctx->completion_lock);
		} else {
			io_put_req(req);
		}
	}
	io_commit_cqring(ctx);
	spin_unlock_irq(&ctx->completion_lock);

	io_cqring_ev_posted(ctx);
	cs->nr = 0;
}

static void __io_req_complete(struct io_kiocb *req, long res, unsigned cflags,
			      struct io_comp_state *cs)
{
	if (!cs) {
		io_cqring_add_event(req, res, cflags);
		io_put_req(req);
	} else {
		io_clean_op(req);
		req->result = res;
		req->compl.cflags = cflags;
		list_add_tail(&req->compl.list, &cs->list);
		if (++cs->nr >= 32)
			io_submit_flush_completions(cs);
	}
}

static void io_req_complete(struct io_kiocb *req, long res)
{
	__io_req_complete(req, res, 0, NULL);
}

static inline bool io_is_fallback_req(struct io_kiocb *req)
{
	return req == (struct io_kiocb *)
			((unsigned long) req->ctx->fallback_req & ~1UL);
}

static struct io_kiocb *io_get_fallback_req(struct io_ring_ctx *ctx)
{
	struct io_kiocb *req;

	req = ctx->fallback_req;
	if (!test_and_set_bit_lock(0, (unsigned long *) &ctx->fallback_req))
		return req;

	return NULL;
}

static struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx,
				     struct io_submit_state *state)
{
	if (!state->free_reqs) {
		gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
		size_t sz;
		int ret;

		sz = min_t(size_t, state->ios_left, ARRAY_SIZE(state->reqs));
		ret = kmem_cache_alloc_bulk(req_cachep, gfp, sz, state->reqs);

		/*
		 * Bulk alloc is all-or-nothing. If we fail to get a batch,
		 * retry single alloc to be on the safe side.
		 */
		if (unlikely(ret <= 0)) {
			state->reqs[0] = kmem_cache_alloc(req_cachep, gfp);
			if (!state->reqs[0])
				goto fallback;
			ret = 1;
		}
		state->free_reqs = ret;
	}

	state->free_reqs--;
	return state->reqs[state->free_reqs];
fallback:
	return io_get_fallback_req(ctx);
}

static inline void io_put_file(struct io_kiocb *req, struct file *file,
			  bool fixed)
{
	if (fixed)
		percpu_ref_put(req->fixed_file_refs);
	else
		fput(file);
}

static void io_dismantle_req(struct io_kiocb *req)
{
	io_clean_op(req);

	if (req->async_data)
		kfree(req->async_data);
	if (req->file)
		io_put_file(req, req->file, (req->flags & REQ_F_FIXED_FILE));

	io_req_clean_work(req);
}

static void __io_free_req(struct io_kiocb *req)
{
	struct io_uring_task *tctx = req->task->io_uring;
	struct io_ring_ctx *ctx = req->ctx;

	io_dismantle_req(req);

	percpu_counter_dec(&tctx->inflight);
	if (atomic_read(&tctx->in_idle))
		wake_up(&tctx->wait);
	put_task_struct(req->task);

	if (likely(!io_is_fallback_req(req)))
		kmem_cache_free(req_cachep, req);
	else
		clear_bit_unlock(0, (unsigned long *) &ctx->fallback_req);
	percpu_ref_put(&ctx->refs);
}

static void io_kill_linked_timeout(struct io_kiocb *req)
{
	struct io_ring_ctx *ctx = req->ctx;
	struct io_kiocb *link;
	bool cancelled = false;
	unsigned long flags;

	spin_lock_irqsave(&ctx->completion_lock, flags);
	link = list_first_entry_or_null(&req->link_list, struct io_kiocb,
					link_list);
	/*
	 * Can happen if a linked timeout fired and link had been like
	 * req -> link t-out -> link t-out [-> ...]
	 */
	if (link && (link->flags & REQ_F_LTIMEOUT_ACTIVE)) {
		struct io_timeout_data *io = link->async_data;
		int ret;

		list_del_init(&link->link_list);
		ret = hrtimer_try_to_cancel(&io->timer);
		if (ret != -1) {
			io_cqring_fill_event(link, -ECANCELED);
			io_commit_cqring(ctx);
			cancelled = true;
		}
	}
	req->flags &= ~REQ_F_LINK_TIMEOUT;
	spin_unlock_irqrestore(&ctx->completion_lock, flags);

	if (cancelled) {
		io_cqring_ev_posted(ctx);
		io_put_req(link);
	}
}

static struct io_kiocb *io_req_link_next(struct io_kiocb *req)
{
	struct io_kiocb *nxt;

	/*
	 * The list should never be empty when we are called here. But could
	 * potentially happen if the chain is messed up, check to be on the
	 * safe side.
	 */
	if (unlikely(list_empty(&req->link_list)))
		return NULL;

	nxt = list_first_entry(&req->link_list, struct io_kiocb, link_list);
	list_del_init(&req->link_list);
	if (!list_empty(&nxt->link_list))
		nxt->flags |= REQ_F_LINK_HEAD;
	return nxt;
}

/*
 * Called if REQ_F_LINK_HEAD is set, and we fail the head request
 */
static void io_fail_links(struct io_kiocb *req)
{
	struct io_ring_ctx *ctx = req->ctx;
	unsigned long flags;

	spin_lock_irqsave(&ctx->completion_lock, flags);
	while (!list_empty(&req->link_list)) {
		struct io_kiocb *link = list_first_entry(&req->link_list,
						struct io_kiocb, link_list);

		list_del_init(&link->link_list);
		trace_io_uring_fail_link(req, link);

		io_cqring_fill_event(link, -ECANCELED);

		/*
		 * It's ok to free under spinlock as they're not linked anymore,
		 * but avoid REQ_F_WORK_INITIALIZED because it may deadlock on
		 * work.fs->lock.
		 */
		if (link->flags & REQ_F_WORK_INITIALIZED)
			io_put_req_deferred(link, 2);
		else
			io_double_put_req(link);
	}

	io_commit_cqring(ctx);
	spin_unlock_irqrestore(&ctx->completion_lock, flags);

	io_cqring_ev_posted(ctx);
}

static struct io_kiocb *__io_req_find_next(struct io_kiocb *req)
{
	req->flags &= ~REQ_F_LINK_HEAD;
	if (req->flags & REQ_F_LINK_TIMEOUT)
		io_kill_linked_timeout(req);

	/*
	 * If LINK is set, we have dependent requests in this chain. If we
	 * didn't fail this request, queue the first one up, moving any other
	 * dependencies to the next request. In case of failure, fail the rest
	 * of the chain.
	 */
	if (likely(!(req->flags & REQ_F_FAIL_LINK)))
		return io_req_link_next(req);
	io_fail_links(req);
	return NULL;
}

static struct io_kiocb *io_req_find_next(struct io_kiocb *req)
{
	if (likely(!(req->flags & REQ_F_LINK_HEAD)))
		return NULL;
	return __io_req_find_next(req);
}

static int io_req_task_work_add(struct io_kiocb *req, bool twa_signal_ok)
{
	struct task_struct *tsk = req->task;
	struct io_ring_ctx *ctx = req->ctx;
	enum task_work_notify_mode notify;
	int ret;

	if (tsk->flags & PF_EXITING)
		return -ESRCH;

	/*
	 * SQPOLL kernel thread doesn't need notification, just a wakeup. For
	 * all other cases, use TWA_SIGNAL unconditionally to ensure we're
	 * processing task_work. There's no reliable way to tell if TWA_RESUME
	 * will do the job.
	 */
	notify = TWA_NONE;
	if (!(ctx->flags & IORING_SETUP_SQPOLL) && twa_signal_ok)
		notify = TWA_SIGNAL;

	ret = task_work_add(tsk, &req->task_work, notify);
	if (!ret)
		wake_up_process(tsk);

	return ret;
}

static void __io_req_task_cancel(struct io_kiocb *req, int error)
{
	struct io_ring_ctx *ctx = req->ctx;

	spin_lock_irq(&ctx->completion_lock);
	io_cqring_fill_event(req, error);
	io_commit_cqring(ctx);
	spin_unlock_irq(&ctx->completion_lock);

	io_cqring_ev_posted(ctx);
	req_set_fail_links(req);
	io_double_put_req(req);
}

static void io_req_task_cancel(struct callback_head *cb)
{
	struct io_kiocb *req = container_of(cb, struct io_kiocb, task_work);
	struct io_ring_ctx *ctx = req->ctx;

	mutex_lock(&ctx->uring_lock);
	__io_req_task_cancel(req, -ECANCELED);
	mutex_unlock(&ctx->uring_lock);
	percpu_ref_put(&ctx->refs);
}

static void __io_req_task_submit(struct io_kiocb *req)
{
	struct io_ring_ctx *ctx = req->ctx;

	mutex_lock(&ctx->uring_lock);
	if (!ctx->sqo_dead && !__io_sq_thread_acquire_mm(ctx))
		__io_queue_sqe(req, NULL);
	else
		__io_req_task_cancel(req, -EFAULT);
	mutex_unlock(&ctx->uring_lock);

	if (ctx->flags & IORING_SETUP_SQPOLL)
		io_sq_thread_drop_mm();
}

static void io_req_task_submit(struct callback_head *cb)
{
	struct io_kiocb *req = container_of(cb, struct io_kiocb, task_work);
	struct io_ring_ctx *ctx = req->ctx;

	__io_req_task_submit(req);
	percpu_ref_put(&ctx->refs);
}

static void io_req_task_queue(struct io_kiocb *req)
{
	int ret;

	init_task_work(&req->task_work, io_req_task_submit);
	percpu_ref_get(&req->ctx->refs);

	ret = io_req_task_work_add(req, true);
	if (unlikely(ret)) {
		struct task_struct *tsk;

		init_task_work(&req->task_work, io_req_task_cancel);
		tsk = io_wq_get_task(req->ctx->io_wq);
		task_work_add(tsk, &req->task_work, TWA_NONE);
		wake_up_process(tsk);
	}
}

static void io_queue_next(struct io_kiocb *req)
{
	struct io_kiocb *nxt = io_req_find_next(req);

	if (nxt)
		io_req_task_queue(nxt);
}

static void io_free_req(struct io_kiocb *req)
{
	io_queue_next(req);
	__io_free_req(req);
}

struct req_batch {
	void *reqs[IO_IOPOLL_BATCH];
	int to_free;

	struct task_struct	*task;
	int			task_refs;
};

static inline void io_init_req_batch(struct req_batch *rb)
{
	rb->to_free = 0;
	rb->task_refs = 0;
	rb->task = NULL;
}

static void __io_req_free_batch_flush(struct io_ring_ctx *ctx,
				      struct req_batch *rb)
{
	kmem_cache_free_bulk(req_cachep, rb->to_free, rb->reqs);
	percpu_ref_put_many(&ctx->refs, rb->to_free);
	rb->to_free = 0;
}

static void io_req_free_batch_finish(struct io_ring_ctx *ctx,
				     struct req_batch *rb)
{
	if (rb->to_free)
		__io_req_free_batch_flush(ctx, rb);
	if (rb->task) {
		struct io_uring_task *tctx = rb->task->io_uring;

		percpu_counter_sub(&tctx->inflight, rb->task_refs);
		if (atomic_read(&tctx->in_idle))
			wake_up(&tctx->wait);
		put_task_struct_many(rb->task, rb->task_refs);
		rb->task = NULL;
	}
}

static void io_req_free_batch(struct req_batch *rb, struct io_kiocb *req)
{
	if (unlikely(io_is_fallback_req(req))) {
		io_free_req(req);
		return;
	}
	if (req->flags & REQ_F_LINK_HEAD)
		io_queue_next(req);

	if (req->task != rb->task) {
		if (rb->task) {
			struct io_uring_task *tctx = rb->task->io_uring;

			percpu_counter_sub(&tctx->inflight, rb->task_refs);
			if (atomic_read(&tctx->in_idle))
				wake_up(&tctx->wait);
			put_task_struct_many(rb->task, rb->task_refs);
		}
		rb->task = req->task;
		rb->task_refs = 0;
	}
	rb->task_refs++;

	io_dismantle_req(req);
	rb->reqs[rb->to_free++] = req;
	if (unlikely(rb->to_free == ARRAY_SIZE(rb->reqs)))
		__io_req_free_batch_flush(req->ctx, rb);
}

/*
 * Drop reference to request, return next in chain (if there is one) if this
 * was the last reference to this request.
 */
static struct io_kiocb *io_put_req_find_next(struct io_kiocb *req)
{
	struct io_kiocb *nxt = NULL;

	if (refcount_dec_and_test(&req->refs)) {
		nxt = io_req_find_next(req);
		__io_free_req(req);
	}
	return nxt;
}

static void io_put_req(struct io_kiocb *req)
{
	if (refcount_dec_and_test(&req->refs))
		io_free_req(req);
}

static void io_put_req_deferred_cb(struct callback_head *cb)
{
	struct io_kiocb *req = container_of(cb, struct io_kiocb, task_work);

	io_free_req(req);
}

static void io_free_req_deferred(struct io_kiocb *req)
{
	int ret;

	init_task_work(&req->task_work, io_put_req_deferred_cb);
	ret = io_req_task_work_add(req, true);
	if (unlikely(ret)) {
		struct task_struct *tsk;

		tsk = io_wq_get_task(req->ctx->io_wq);
		task_work_add(tsk, &req->task_work, TWA_NONE);
		wake_up_process(tsk);
	}
}

static inline void io_put_req_deferred(struct io_kiocb *req, int refs)
{
	if (refcount_sub_and_test(refs, &req->refs))
		io_free_req_deferred(req);
}

static struct io_wq_work *io_steal_work(struct io_kiocb *req)
{
	struct io_kiocb *nxt;

	/*
	 * A ref is owned by io-wq in which context we're. So, if that's the
	 * last one, it's safe to steal next work. False negatives are Ok,
	 * it just will be re-punted async in io_put_work()
	 */
	if (refcount_read(&req->refs) != 1)
		return NULL;

	nxt = io_req_find_next(req);
	return nxt ? &nxt->work : NULL;
}

static void io_double_put_req(struct io_kiocb *req)
{
	/* drop both submit and complete references */
	if (refcount_sub_and_test(2, &req->refs))
		io_free_req(req);
}

static unsigned io_cqring_events(struct io_ring_ctx *ctx)
{
	struct io_rings *rings = ctx->rings;

	/* See comment at the top of this file */
	smp_rmb();
	return ctx->cached_cq_tail - READ_ONCE(rings->cq.head);
}

static inline unsigned int io_sqring_entries(struct io_ring_ctx *ctx)
{
	struct io_rings *rings = ctx->rings;

	/* make sure SQ entry isn't read before tail */
	return smp_load_acquire(&rings->sq.tail) - ctx->cached_sq_head;
}

static unsigned int io_put_kbuf(struct io_kiocb *req, struct io_buffer *kbuf)
{
	unsigned int cflags;

	cflags = kbuf->bid << IORING_CQE_BUFFER_SHIFT;
	cflags |= IORING_CQE_F_BUFFER;
	req->flags &= ~REQ_F_BUFFER_SELECTED;
	kfree(kbuf);
	return cflags;
}

static inline unsigned int io_put_rw_kbuf(struct io_kiocb *req)
{
	struct io_buffer *kbuf;

	kbuf = (struct io_buffer *) (unsigned long) req->rw.addr;
	return io_put_kbuf(req, kbuf);
}

static inline bool io_run_task_work(void)
{
	/*
	 * Not safe to run on exiting task, and the task_work handling will
	 * not add work to such a task.
	 */
	if (unlikely(current->flags & PF_EXITING))
		return false;
	if (current->task_works) {
		__set_current_state(TASK_RUNNING);
		task_work_run();
		return true;
	}

	return false;
}

static void io_iopoll_queue(struct list_head *again)
{
	struct io_kiocb *req;

	do {
		req = list_first_entry(again, struct io_kiocb, inflight_entry);
		list_del(&req->inflight_entry);
		__io_complete_rw(req, -EAGAIN, 0, NULL);
	} while (!list_empty(again));
}

/*
 * Find and free completed poll iocbs
 */
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;
	LIST_HEAD(again);

	/* 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);
		if (READ_ONCE(req->result) == -EAGAIN) {
			req->result = 0;
			req->iopoll_completed = 0;
			list_move_tail(&req->inflight_entry, &again);
			continue;
		}
		list_del(&req->inflight_entry);

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

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

		if (refcount_dec_and_test(&req->refs))
			io_req_free_batch(&rb, req);
	}

	io_commit_cqring(ctx);
	if (ctx->flags & IORING_SETUP_SQPOLL)
		io_cqring_ev_posted(ctx);
	io_req_free_batch_finish(ctx, &rb);

	if (!list_empty(&again))
		io_iopoll_queue(&again);
}

static int io_do_iopoll(struct io_ring_ctx *ctx, unsigned int *nr_events,
			long min)
{
	struct io_kiocb *req, *tmp;
	LIST_HEAD(done);
	bool spin;
	int ret;

	/*
	 * Only spin for completions if we don't have multiple devices hanging
	 * off our complete list, and we're under the requested amount.
	 */
	spin = !ctx->poll_multi_file && *nr_events < min;

	ret = 0;
	list_for_each_entry_safe(req, tmp, &ctx->iopoll_list, inflight_entry) {
		struct kiocb *kiocb = &req->rw.kiocb;

		/*
		 * Move completed and retryable entries to our local lists.
		 * If we find a request that requires polling, break out
		 * and complete those lists first, if we have entries there.
		 */
		if (READ_ONCE(req->iopoll_completed)) {
			list_move_tail(&req->inflight_entry, &done);
			continue;
		}
		if (!list_empty(&done))
			break;

		ret = kiocb->ki_filp->f_op->iopoll(kiocb, spin);
		if (ret < 0)
			break;

		/* iopoll may have completed current req */
		if (READ_ONCE(req->iopoll_completed))
			list_move_tail(&req->inflight_entry, &done);

		if (ret && spin)
			spin = false;
		ret = 0;
	}

	if (!list_empty(&done))
		io_iopoll_complete(ctx, nr_events, &done);

	return ret;
}

/*
 * Poll for a minimum of 'min' events. Note that if min == 0 we consider that a
 * non-spinning poll check - we'll still enter the driver poll loop, but only
 * as a non-spinning completion check.
 */
static int io_iopoll_getevents(struct io_ring_ctx *ctx, unsigned int *nr_events,
				long min)
{
	while (!list_empty(&ctx->iopoll_list) && !need_resched()) {
		int ret;

		ret = io_do_iopoll(ctx, nr_events, min);
		if (ret < 0)
			return ret;
		if (*nr_events >= min)
			return 0;
	}

	return 1;
}

/*
 * We can't just wait for polled events to come to us, we have to actively
 * find and complete them.
 */
static void io_iopoll_try_reap_events(struct io_ring_ctx *ctx)
{
	if (!(ctx->flags & IORING_SETUP_IOPOLL))
		return;

	mutex_lock(&ctx->uring_lock);
	while (!list_empty(&ctx->iopoll_list)) {
		unsigned int nr_events = 0;

		io_do_iopoll(ctx, &nr_events, 0);

		/* let it sleep and repeat later if can't complete a request */
		if (nr_events == 0)
			break;
		/*
		 * Ensure we allow local-to-the-cpu processing to take place,
		 * in this case we need to ensure that we reap all events.
		 * Also let task_work, etc. to progress by releasing the mutex
		 */
		if (need_resched()) {
			mutex_unlock(&ctx->uring_lock);
			cond_resched();
			mutex_lock(&ctx->uring_lock);
		}
	}
	mutex_unlock(&ctx->uring_lock);
}

static int io_iopoll_check(struct io_ring_ctx *ctx, long min)
{
	unsigned int nr_events = 0;
	int iters = 0, ret = 0;

	/*
	 * We disallow the app entering submit/complete with polling, but we
	 * still need to lock the ring to prevent racing with polled issue
	 * that got punted to a workqueue.
	 */
	mutex_lock(&ctx->uring_lock);
	do {
		/*
		 * Don't enter poll loop if we already have events pending.
		 * If we do, we can potentially be spinning for commands that
		 * already triggered a CQE (eg in error).
		 */
		if (test_bit(0, &ctx->cq_check_overflow))
			__io_cqring_overflow_flush(ctx, false, NULL, NULL);
		if (io_cqring_events(ctx))
			break;

		/*
		 * If a submit got punted to a workqueue, we can have the
		 * application entering polling for a command before it gets
		 * issued. That app will hold the uring_lock for the duration
		 * of the poll right here, so we need to take a breather every
		 * now and then to ensure that the issue has a chance to add
		 * the poll to the issued list. Otherwise we can spin here
		 * forever, while the workqueue is stuck trying to acquire the
		 * very same mutex.
		 */
		if (!(++iters & 7)) {
			mutex_unlock(&ctx->uring_lock);
			io_run_task_work();
			mutex_lock(&ctx->uring_lock);
		}

		ret = io_iopoll_getevents(ctx, &nr_events, min);
		if (ret <= 0)
			break;
		ret = 0;
	} while (min && !nr_events && !need_resched());

	mutex_unlock(&ctx->uring_lock);
	return ret;
}

static void kiocb_end_write(struct io_kiocb *req)
{
	/*
	 * Tell lockdep we inherited freeze protection from submission
	 * thread.
	 */
	if (req->flags & REQ_F_ISREG) {
		struct inode *inode = file_inode(req->file);

		__sb_writers_acquired(inode->i_sb, SB_FREEZE_WRITE);
	}
	file_end_write(req->file);
}

static void io_complete_rw_common(struct kiocb *kiocb, long res,
				  struct io_comp_state *cs)
{
	struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw.kiocb);
	int cflags = 0;

	if (kiocb->ki_flags & IOCB_WRITE)
		kiocb_end_write(req);

	if (res != req->result)
		req_set_fail_links(req);
	if (req->flags & REQ_F_BUFFER_SELECTED)
		cflags = io_put_rw_kbuf(req);
	__io_req_complete(req, res, cflags, cs);
}

#ifdef CONFIG_BLOCK
static bool io_resubmit_prep(struct io_kiocb *req, int error)
{
	struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
	ssize_t ret = -ECANCELED;
	struct iov_iter iter;
	int rw;

	if (error) {
		ret = error;
		goto end_req;
	}

	switch (req->opcode) {
	case IORING_OP_READV:
	case IORING_OP_READ_FIXED:
	case IORING_OP_READ:
		rw = READ;
		break;
	case IORING_OP_WRITEV:
	case IORING_OP_WRITE_FIXED:
	case IORING_OP_WRITE:
		rw = WRITE;
		break;
	default:
		printk_once(KERN_WARNING "io_uring: bad opcode in resubmit %d\n",
				req->opcode);
		goto end_req;
	}

	if (!req->async_data) {
		ret = io_import_iovec(rw, req, &iovec, &iter, false);
		if (ret < 0)
			goto end_req;
		ret = io_setup_async_rw(req, iovec, inline_vecs, &iter, false);
		if (!ret)
			return true;
		kfree(iovec);
	} else {
		return true;
	}
end_req:
	req_set_fail_links(req);
	return false;
}
#endif

static bool io_rw_reissue(struct io_kiocb *req, long res)
{
#ifdef CONFIG_BLOCK
	umode_t mode = file_inode(req->file)->i_mode;
	int ret;

	if (!S_ISBLK(mode) && !S_ISREG(mode))
		return false;
	if ((res != -EAGAIN && res != -EOPNOTSUPP) || io_wq_current_is_worker())
		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(&req->ctx->refs))
		return false;

	ret = io_sq_thread_acquire_mm(req->ctx, req);

	if (io_resubmit_prep(req, ret)) {
		refcount_inc(&req->refs);
		io_queue_async_work(req);
		return true;
	}

#endif
	return false;
}

static void __io_complete_rw(struct io_kiocb *req, long res, long res2,
			     struct io_comp_state *cs)
{
	if (!io_rw_reissue(req, res))
		io_complete_rw_common(&req->rw.kiocb, res, cs);
}

static void io_complete_rw(struct kiocb *kiocb, long res, long res2)
{
	struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw.kiocb);

	__io_complete_rw(req, res, res2, NULL);
}

static void io_complete_rw_iopoll(struct kiocb *kiocb, long res, long res2)
{
	struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw.kiocb);

	if (kiocb->ki_flags & IOCB_WRITE)
		kiocb_end_write(req);

	if (res != -EAGAIN && res != req->result)
		req_set_fail_links(req);

	WRITE_ONCE(req->result, res);
	/* order with io_poll_complete() checking ->result */
	smp_wmb();
	WRITE_ONCE(req->iopoll_completed, 1);
}

/*
 * After the iocb has been issued, it's safe to be found on the poll list.
 * Adding the kiocb to the list AFTER submission ensures that we don't
 * find it from a io_iopoll_getevents() thread before the issuer is done
 * accessing the kiocb cookie.
 */
static void io_iopoll_req_issued(struct io_kiocb *req)
{
	struct io_ring_ctx *ctx = req->ctx;

	/*
	 * Track whether we have multiple files in our lists. This will impact
	 * how we do polling eventually, not spinning if we're on potentially
	 * different devices.
	 */
	if (list_empty(&ctx->iopoll_list)) {
		ctx->poll_multi_file = false;
	} else if (!ctx->poll_multi_file) {
		struct io_kiocb *list_req;

		list_req = list_first_entry(&ctx->iopoll_list, struct io_kiocb,
						inflight_entry);
		if (list_req->file != req->file)
			ctx->poll_multi_file = true;
	}

	/*
	 * For fast devices, IO may have already completed. If it has, add
	 * it to the front so we find it first.
	 */
	if (READ_ONCE(req->iopoll_completed))
		list_add(&req->inflight_entry, &ctx->iopoll_list);
	else
		list_add_tail(&req->inflight_entry, &ctx->iopoll_list);

	if ((ctx->flags & IORING_SETUP_SQPOLL) &&
	    wq_has_sleeper(&ctx->sq_data->wait))
		wake_up(&ctx->sq_data->wait);
}

static void __io_state_file_put(struct io_submit_state *state)
{
	if (state->has_refs)
		fput_many(state->file, state->has_refs);
	state->file = NULL;
}

static inline void io_state_file_put(struct io_submit_state *state)
{
	if (state->file)
		__io_state_file_put(state);
}

/*
 * Get as many references to a file as we have IOs left in this submission,
 * assuming most submissions are for one file, or at least that each file
 * has more than one submission.
 */
static struct file *__io_file_get(struct io_submit_state *state, int fd)
{
	if (!state)
		return fget(fd);

	if (state->file) {
		if (state->fd == fd) {
			state->has_refs--;
			return state->file;
		}
		__io_state_file_put(state);
	}
	state->file = fget_many(fd, state->ios_left);
	if (!state->file)
		return NULL;

	state->fd = fd;
	state->has_refs = state->ios_left - 1;
	return state->file;
}

static bool io_bdev_nowait(struct block_device *bdev)
{
#ifdef CONFIG_BLOCK
	return !bdev || blk_queue_nowait(bdev_get_queue(bdev));
#else
	return true;
#endif
}

/*
 * If we tracked the file through the SCM inflight mechanism, we could support
 * any file. For now, just ensure that anything potentially problematic is done
 * inline.
 */
static bool io_file_supports_async(struct file *file, int rw)
{
	umode_t mode = file_inode(file)->i_mode;

	if (S_ISBLK(mode)) {
		if (io_bdev_nowait(file->f_inode->i_bdev))
			return true;
		return false;
	}
	if (S_ISSOCK(mode))
		return true;
	if (S_ISREG(mode)) {
		if (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 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;
	unsigned ioprio;
	int ret;

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

	kiocb->ki_pos = READ_ONCE(sqe->off);
	if (kiocb->ki_pos == -1 && !(req->file->f_mode & FMODE_STREAM)) {
		req->flags |= REQ_F_CUR_POS;
		kiocb->ki_pos = req->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;

	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();

	/* don't allow async punt if RWF_NOWAIT was requested */
	if (kiocb->ki_flags & IOCB_NOWAIT)
		req->flags |= REQ_F_NOWAIT;

	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;
	}

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

static inline void io_rw_done(struct kiocb *kiocb, ssize_t ret)
{
	switch (ret) {
	case -EIOCBQUEUED:
		break;
	case -ERESTARTSYS:
	case -ERESTARTNOINTR:
	case -ERESTARTNOHAND:
	case -ERESTART_RESTARTBLOCK:
		/*
		 * We can't just restart the syscall, since previously
		 * submitted sqes may already be in progress. Just fail this
		 * IO with EINTR.
		 */
		ret = -EINTR;
		fallthrough;
	default:
		kiocb->ki_complete(kiocb, ret, 0);
	}
}

static void kiocb_done(struct kiocb *kiocb, ssize_t ret,
		       struct io_comp_state *cs)
{
	struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw.kiocb);
	struct io_async_rw *io = req->async_data;

	/* add previously done IO, if any */
	if (io && io->bytes_done > 0) {
		if (ret < 0)
			ret = io->bytes_done;
		else
			ret += io->bytes_done;
	}

	if (req->flags & REQ_F_CUR_POS)
		req->file->f_pos = kiocb->ki_pos;
	if (ret >= 0 && kiocb->ki_complete == io_complete_rw)
		__io_complete_rw(req, ret, 0, cs);
	else
		io_rw_done(kiocb, ret);
}

static ssize_t io_import_fixed(struct io_kiocb *req, int rw,
			       struct iov_iter *iter)
{
	struct io_ring_ctx *ctx = req->ctx;
	size_t len = req->rw.len;
	struct io_mapped_ubuf *imu;
	u16 index, buf_index = req->buf_index;
	size_t offset;
	u64 buf_addr;

	if (unlikely(buf_index >= ctx->nr_user_bufs))
		return -EFAULT;
	index = array_index_nospec(buf_index, ctx->nr_user_bufs);
	imu = &ctx->user_bufs[index];
	buf_addr = req->rw.addr;

	/* overflow */
	if (buf_addr + len < buf_addr)
		return -EFAULT;
	/* not inside the mapped region */
	if (buf_addr < imu->ubuf || buf_addr + len > imu->ubuf + imu->len)
		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 len;
}

static void io_ring_submit_unlock(struct io_ring_ctx *ctx, bool needs_lock)
{
	if (needs_lock)
		mutex_unlock(&ctx->uring_lock);
}

static void io_ring_submit_lock(struct io_ring_ctx *ctx, bool needs_lock)
{
	/*
	 * "Normal" inline submissions always hold the uring_lock, since we
	 * grab it from the system call. Same is true for the SQPOLL offload.
	 * The only exception is when we've detached the request and issue it
	 * from an async worker thread, grab the lock for that case.
	 */
	if (needs_lock)
		mutex_lock(&ctx->uring_lock);
}

static struct io_buffer *io_buffer_select(struct io_kiocb *req, size_t *len,
					  int bgid, struct io_buffer *kbuf,
					  bool needs_lock)
{
	struct io_buffer *head;

	if (req->flags & REQ_F_BUFFER_SELECTED)
		return kbuf;

	io_ring_submit_lock(req->ctx, needs_lock);

	lockdep_assert_held(&req->ctx->uring_lock);

	head = xa_load(&req->ctx->io_buffers, bgid);
	if (head) {
		if (!list_empty(&head->list)) {
			kbuf = list_last_entry(&head->list, struct io_buffer,
							list);
			list_del(&kbuf->list);
		} else {
			kbuf = head;
			xa_erase(&req->ctx->io_buffers, bgid);
		}
		if (*len > kbuf->len)
			*len = kbuf->len;
	} else {
		kbuf = ERR_PTR(-ENOBUFS);
	}

	io_ring_submit_unlock(req->ctx, needs_lock);

	return kbuf;
}

static void __user *io_rw_buffer_select(struct io_kiocb *req, size_t *len,
					bool needs_lock)
{
	struct io_buffer *kbuf;
	u16 bgid;

	kbuf = (struct io_buffer *) (unsigned long) req->rw.addr;
	bgid = req->buf_index;
	kbuf = io_buffer_select(req, len, bgid, kbuf, needs_lock);
	if (IS_ERR(kbuf))
		return kbuf;
	req->rw.addr = (u64) (unsigned long) kbuf;
	req->flags |= REQ_F_BUFFER_SELECTED;
	return u64_to_user_ptr(kbuf->addr);
}

#ifdef CONFIG_COMPAT
static ssize_t io_compat_import(struct io_kiocb *req, struct iovec *iov,
				bool needs_lock)
{
	struct compat_iovec __user *uiov;
	compat_ssize_t clen;
	void __user *buf;
	ssize_t len;

	uiov = u64_to_user_ptr(req->rw.addr);
	if (!access_ok(uiov, sizeof(*uiov)))
		return -EFAULT;
	if (__get_user(clen, &uiov->iov_len))
		return -EFAULT;
	if (clen < 0)
		return -EINVAL;

	len = clen;
	buf = io_rw_buffer_select(req, &len, needs_lock);
	if (IS_ERR(buf))
		return PTR_ERR(buf);
	iov[0].iov_base = buf;
	iov[0].iov_len = (compat_size_t) len;
	return 0;
}
#endif

static ssize_t __io_iov_buffer_select(struct io_kiocb *req, struct iovec *iov,
				      bool needs_lock)
{
	struct iovec __user *uiov = u64_to_user_ptr(req->rw.addr);
	void __user *buf;
	ssize_t len;

	if (copy_from_user(iov, uiov, sizeof(*uiov)))
		return -EFAULT;

	len = iov[0].iov_len;
	if (len < 0)
		return -EINVAL;
	buf = io_rw_buffer_select(req, &len, needs_lock);
	if (IS_ERR(buf))
		return PTR_ERR(buf);
	iov[0].iov_base = buf;
	iov[0].iov_len = len;
	return 0;
}

static ssize_t io_iov_buffer_select(struct io_kiocb *req, struct iovec *iov,
				    bool needs_lock)
{
	if (req->flags & REQ_F_BUFFER_SELECTED) {
		struct io_buffer *kbuf;

		kbuf = (struct io_buffer *) (unsigned long) req->rw.addr;
		iov[0].iov_base = u64_to_user_ptr(kbuf->addr);
		iov[0].iov_len = kbuf->len;
		return 0;
	}
	if (req->rw.len != 1)
		return -EINVAL;

#ifdef CONFIG_COMPAT
	if (req->ctx->compat)
		return io_compat_import(req, iov, needs_lock);
#endif

	return __io_iov_buffer_select(req, iov, needs_lock);
}

static ssize_t __io_import_iovec(int rw, struct io_kiocb *req,
				 struct iovec **iovec, struct iov_iter *iter,
				 bool needs_lock)
{
	void __user *buf = u64_to_user_ptr(req->rw.addr);
	size_t sqe_len = req->rw.len;
	ssize_t ret;
	u8 opcode;

	opcode = req->opcode;
	if (opcode == IORING_OP_READ_FIXED || opcode == IORING_OP_WRITE_FIXED) {
		*iovec = NULL;
		return io_import_fixed(req, rw, iter);
	}

	/* buffer index only valid with fixed read/write, or buffer select  */
	if (req->buf_index && !(req->flags & REQ_F_BUFFER_SELECT))
		return -EINVAL;

	if (opcode == IORING_OP_READ || opcode == IORING_OP_WRITE) {
		if (req->flags & REQ_F_BUFFER_SELECT) {
			buf = io_rw_buffer_select(req, &sqe_len, needs_lock);
			if (IS_ERR(buf))
				return PTR_ERR(buf);
			req->rw.len = sqe_len;
		}

		ret = import_single_range(rw, buf, sqe_len, *iovec, iter);
		*iovec = NULL;
		return ret;
	}

	if (req->flags & REQ_F_BUFFER_SELECT) {
		ret = io_iov_buffer_select(req, *iovec, needs_lock);
		if (!ret) {
			ret = (*iovec)->iov_len;
			iov_iter_init(iter, rw, *iovec, 1, ret);
		}
		*iovec = NULL;
		return ret;
	}

	return __import_iovec(rw, buf, sqe_len,