io_uring: move read/write related opcodes to its own file

Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 1099 insertions, 0 deletions

diff --git a/io_uring/rw.c b/io_uring/rw.c
new file mode 100644
index 000000000000..f0b60199ee22
--- /dev/null
+++ b/io_uring/rw.c
@@ -0,0 +1,1099 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/blk-mq.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/fsnotify.h>
+#include <linux/poll.h>
+#include <linux/nospec.h>
+#include <linux/compat.h>
+#include <linux/io_uring.h>
+
+#include <uapi/linux/io_uring.h>
+
+#include "io_uring_types.h"
+#include "io_uring.h"
+#include "opdef.h"
+#include "kbuf.h"
+#include "rsrc.h"
+#include "rw.h"
+
+struct io_rw {
+	/* NOTE: kiocb has the file as the first member, so don't do it here */
+	struct kiocb			kiocb;
+	u64				addr;
+	u32				len;
+	rwf_t				flags;
+};
+
+static inline bool io_file_supports_nowait(struct io_kiocb *req)
+{
+	return req->flags & REQ_F_SUPPORT_NOWAIT;
+}
+
+int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_rw *rw = io_kiocb_to_cmd(req);
+	unsigned ioprio;
+	int ret;
+
+	rw->kiocb.ki_pos = READ_ONCE(sqe->off);
+	/* used for fixed read/write too - just read unconditionally */
+	req->buf_index = READ_ONCE(sqe->buf_index);
+
+	if (req->opcode == IORING_OP_READ_FIXED ||
+	    req->opcode == IORING_OP_WRITE_FIXED) {
+		struct io_ring_ctx *ctx = req->ctx;
+		u16 index;
+
+		if (unlikely(req->buf_index >= ctx->nr_user_bufs))
+			return -EFAULT;
+		index = array_index_nospec(req->buf_index, ctx->nr_user_bufs);
+		req->imu = ctx->user_bufs[index];
+		io_req_set_rsrc_node(req, ctx, 0);
+	}
+
+	ioprio = READ_ONCE(sqe->ioprio);
+	if (ioprio) {
+		ret = ioprio_check_cap(ioprio);
+		if (ret)
+			return ret;
+
+		rw->kiocb.ki_ioprio = ioprio;
+	} else {
+		rw->kiocb.ki_ioprio = get_current_ioprio();
+	}
+
+	rw->addr = READ_ONCE(sqe->addr);
+	rw->len = READ_ONCE(sqe->len);
+	rw->flags = READ_ONCE(sqe->rw_flags);
+	return 0;
+}
+
+void io_readv_writev_cleanup(struct io_kiocb *req)
+{
+	struct io_async_rw *io = req->async_data;
+
+	kfree(io->free_iovec);
+}
+
+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);
+	}
+}
+
+static inline loff_t *io_kiocb_update_pos(struct io_kiocb *req)
+{
+	struct io_rw *rw = io_kiocb_to_cmd(req);
+
+	if (rw->kiocb.ki_pos != -1)
+		return &rw->kiocb.ki_pos;
+
+	if (!(req->file->f_mode & FMODE_STREAM)) {
+		req->flags |= REQ_F_CUR_POS;
+		rw->kiocb.ki_pos = req->file->f_pos;
+		return &rw->kiocb.ki_pos;
+	}
+
+	rw->kiocb.ki_pos = 0;
+	return NULL;
+}
+
+static void io_req_task_queue_reissue(struct io_kiocb *req)
+{
+	req->io_task_work.func = io_queue_iowq;
+	io_req_task_work_add(req);
+}
+
+#ifdef CONFIG_BLOCK
+static bool io_resubmit_prep(struct io_kiocb *req)
+{
+	struct io_async_rw *io = req->async_data;
+
+	if (!req_has_async_data(req))
+		return !io_req_prep_async(req);
+	iov_iter_restore(&io->s.iter, &io->s.iter_state);
+	return true;
+}
+
+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;
+	/*
+	 * Play it safe and assume not safe to re-import and reissue if we're
+	 * not in the original thread group (or in task context).
+	 */
+	if (!same_thread_group(req->task, current) || !in_task())
+		return false;
+	return true;
+}
+#else
+static bool io_resubmit_prep(struct io_kiocb *req)
+{
+	return false;
+}
+static bool io_rw_should_reissue(struct io_kiocb *req)
+{
+	return false;
+}
+#endif
+
+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 super_block *sb = file_inode(req->file)->i_sb;
+
+		__sb_writers_acquired(sb, SB_FREEZE_WRITE);
+		sb_end_write(sb);
+	}
+}
+
+static bool __io_complete_rw_common(struct io_kiocb *req, long res)
+{
+	struct io_rw *rw = io_kiocb_to_cmd(req);
+
+	if (rw->kiocb.ki_flags & IOCB_WRITE) {
+		kiocb_end_write(req);
+		fsnotify_modify(req->file);
+	} else {
+		fsnotify_access(req->file);
+	}
+	if (unlikely(res != req->cqe.res)) {
+		if ((res == -EAGAIN || res == -EOPNOTSUPP) &&
+		    io_rw_should_reissue(req)) {
+			req->flags |= REQ_F_REISSUE | REQ_F_PARTIAL_IO;
+			return true;
+		}
+		req_set_fail(req);
+		req->cqe.res = res;
+	}
+	return false;
+}
+
+static void __io_complete_rw(struct io_kiocb *req, long res,
+			     unsigned int issue_flags)
+{
+	if (__io_complete_rw_common(req, res))
+		return;
+	io_req_set_res(req, req->cqe.res, io_put_kbuf(req, issue_flags));
+	__io_req_complete(req, issue_flags);
+}
+
+static void io_complete_rw(struct kiocb *kiocb, long res)
+{
+	struct io_rw *rw = container_of(kiocb, struct io_rw, kiocb);
+	struct io_kiocb *req = cmd_to_io_kiocb(rw);
+
+	if (__io_complete_rw_common(req, res))
+		return;
+	io_req_set_res(req, res, 0);
+	req->io_task_work.func = io_req_task_complete;
+	io_req_task_prio_work_add(req);
+}
+
+static void io_complete_rw_iopoll(struct kiocb *kiocb, long res)
+{
+	struct io_rw *rw = container_of(kiocb, struct io_rw, kiocb);
+	struct io_kiocb *req = cmd_to_io_kiocb(rw);
+
+	if (kiocb->ki_flags & IOCB_WRITE)
+		kiocb_end_write(req);
+	if (unlikely(res != req->cqe.res)) {
+		if (res == -EAGAIN && io_rw_should_reissue(req)) {
+			req->flags |= REQ_F_REISSUE | REQ_F_PARTIAL_IO;
+			return;
+		}
+		req->cqe.res = res;
+	}
+
+	/* order with io_iopoll_complete() checking ->iopoll_completed */
+	smp_store_release(&req->iopoll_completed, 1);
+}
+
+static void kiocb_done(struct io_kiocb *req, ssize_t ret,
+		       unsigned int issue_flags)
+{
+	struct io_async_rw *io = req->async_data;
+	struct io_rw *rw = io_kiocb_to_cmd(req);
+
+	/* add previously done IO, if any */
+	if (req_has_async_data(req) && 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 = rw->kiocb.ki_pos;
+	if (ret >= 0 && (rw->kiocb.ki_complete == io_complete_rw))
+		__io_complete_rw(req, ret, issue_flags);
+	else
+		io_rw_done(&rw->kiocb, ret);
+
+	if (req->flags & REQ_F_REISSUE) {
+		req->flags &= ~REQ_F_REISSUE;
+		if (io_resubmit_prep(req))
+			io_req_task_queue_reissue(req);
+		else
+			io_req_task_queue_fail(req, ret);
+	}
+}
+
+static int __io_import_fixed(struct io_kiocb *req, int ddir,
+			     struct iov_iter *iter, struct io_mapped_ubuf *imu)
+{
+	struct io_rw *rw = io_kiocb_to_cmd(req);
+	size_t len = rw->len;
+	u64 buf_end, buf_addr = 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, ddir, 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;
+}
+
+static int io_import_fixed(struct io_kiocb *req, int rw, struct iov_iter *iter,
+			   unsigned int issue_flags)
+{
+	if (WARN_ON_ONCE(!req->imu))
+		return -EFAULT;
+	return __io_import_fixed(req, rw, iter, req->imu);
+}
+
+#ifdef CONFIG_COMPAT
+static ssize_t io_compat_import(struct io_kiocb *req, struct iovec *iov,
+				unsigned int issue_flags)
+{
+	struct io_rw *rw = io_kiocb_to_cmd(req);
+	struct compat_iovec __user *uiov;
+	compat_ssize_t clen;
+	void __user *buf;
+	size_t len;
+
+	uiov = u64_to_user_ptr(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_buffer_select(req, &len, issue_flags);
+	if (!buf)
+		return -ENOBUFS;
+	rw->addr = (unsigned long) buf;
+	iov[0].iov_base = buf;
+	rw->len = 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,
+				      unsigned int issue_flags)
+{
+	struct io_rw *rw = io_kiocb_to_cmd(req);
+	struct iovec __user *uiov = u64_to_user_ptr(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_buffer_select(req, &len, issue_flags);
+	if (!buf)
+		return -ENOBUFS;
+	rw->addr = (unsigned long) buf;
+	iov[0].iov_base = buf;
+	rw->len = iov[0].iov_len = len;
+	return 0;
+}
+
+static ssize_t io_iov_buffer_select(struct io_kiocb *req, struct iovec *iov,
+				    unsigned int issue_flags)
+{
+	struct io_rw *rw = io_kiocb_to_cmd(req);
+
+	if (req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)) {
+		iov[0].iov_base = u64_to_user_ptr(rw->addr);
+		iov[0].iov_len = rw->len;
+		return 0;
+	}
+	if (rw->len != 1)
+		return -EINVAL;
+
+#ifdef CONFIG_COMPAT
+	if (req->ctx->compat)
+		return io_compat_import(req, iov, issue_flags);
+#endif
+
+	return __io_iov_buffer_select(req, iov, issue_flags);
+}
+
+static struct iovec *__io_import_iovec(int ddir, struct io_kiocb *req,
+				       struct io_rw_state *s,
+				       unsigned int issue_flags)
+{
+	struct io_rw *rw = io_kiocb_to_cmd(req);
+	struct iov_iter *iter = &s->iter;
+	u8 opcode = req->opcode;
+	struct iovec *iovec;
+	void __user *buf;
+	size_t sqe_len;
+	ssize_t ret;
+
+	if (opcode == IORING_OP_READ_FIXED || opcode == IORING_OP_WRITE_FIXED) {
+		ret = io_import_fixed(req, ddir, iter, issue_flags);
+		if (ret)
+			return ERR_PTR(ret);
+		return NULL;
+	}
+
+	buf = u64_to_user_ptr(rw->addr);
+	sqe_len = rw->len;
+
+	if (opcode == IORING_OP_READ || opcode == IORING_OP_WRITE) {
+		if (io_do_buffer_select(req)) {
+			buf = io_buffer_select(req, &sqe_len, issue_flags);
+			if (!buf)
+				return ERR_PTR(-ENOBUFS);
+			rw->addr = (unsigned long) buf;
+			rw->len = sqe_len;
+		}
+
+		ret = import_single_range(ddir, buf, sqe_len, s->fast_iov, iter);
+		if (ret)
+			return ERR_PTR(ret);
+		return NULL;
+	}
+
+	iovec = s->fast_iov;
+	if (req->flags & REQ_F_BUFFER_SELECT) {
+		ret = io_iov_buffer_select(req, iovec, issue_flags);
+		if (ret)
+			return ERR_PTR(ret);
+		iov_iter_init(iter, ddir, iovec, 1, iovec->iov_len);
+		return NULL;
+	}
+
+	ret = __import_iovec(ddir, buf, sqe_len, UIO_FASTIOV, &iovec, iter,
+			      req->ctx->compat);
+	if (unlikely(ret < 0))
+		return ERR_PTR(ret);
+	return iovec;
+}
+
+static inline int io_import_iovec(int rw, struct io_kiocb *req,
+				  struct iovec **iovec, struct io_rw_state *s,
+				  unsigned int issue_flags)
+{
+	*iovec = __io_import_iovec(rw, req, s, issue_flags);
+	if (unlikely(IS_ERR(*iovec)))
+		return PTR_ERR(*iovec);
+
+	iov_iter_save_state(&s->iter, &s->iter_state);
+	return 0;
+}
+
+static inline loff_t *io_kiocb_ppos(struct kiocb *kiocb)
+{
+	return (kiocb->ki_filp->f_mode & FMODE_STREAM) ? NULL : &kiocb->ki_pos;
+}
+
+/*
+ * For files that don't have ->read_iter() and ->write_iter(), handle them
+ * by looping over ->read() or ->write() manually.
+ */
+static ssize_t loop_rw_iter(int ddir, struct io_rw *rw, struct iov_iter *iter)
+{
+	struct kiocb *kiocb = &rw->kiocb;
+	struct file *file = kiocb->ki_filp;
+	ssize_t ret = 0;
+	loff_t *ppos;
+
+	/*
+	 * Don't support polled IO through this interface, and we can't
+	 * support non-blocking either. For the latter, this just causes
+	 * the kiocb to be handled from an async context.
+	 */
+	if (kiocb->ki_flags & IOCB_HIPRI)
+		return -EOPNOTSUPP;
+	if ((kiocb->ki_flags & IOCB_NOWAIT) &&
+	    !(kiocb->ki_filp->f_flags & O_NONBLOCK))
+		return -EAGAIN;
+
+	ppos = io_kiocb_ppos(kiocb);
+
+	while (iov_iter_count(iter)) {
+		struct iovec iovec;
+		ssize_t nr;
+
+		if (!iov_iter_is_bvec(iter)) {
+			iovec = iov_iter_iovec(iter);
+		} else {
+			iovec.iov_base = u64_to_user_ptr(rw->addr);
+			iovec.iov_len = rw->len;
+		}
+
+		if (ddir == READ) {
+			nr = file->f_op->read(file, iovec.iov_base,
+					      iovec.iov_len, ppos);
+		} else {
+			nr = file->f_op->write(file, iovec.iov_base,
+					       iovec.iov_len, ppos);
+		}
+
+		if (nr < 0) {
+			if (!ret)
+				ret = nr;
+			break;
+		}
+		ret += nr;
+		if (!iov_iter_is_bvec(iter)) {
+			iov_iter_advance(iter, nr);
+		} else {
+			rw->addr += nr;
+			rw->len -= nr;
+			if (!rw->len)
+				break;
+		}
+		if (nr != iovec.iov_len)
+			break;
+	}
+
+	return ret;
+}
+
+static void io_req_map_rw(struct io_kiocb *req, const struct iovec *iovec,
+			  const struct iovec *fast_iov, struct iov_iter *iter)
+{
+	struct io_async_rw *io = req->async_data;
+
+	memcpy(&io->s.iter, iter, sizeof(*iter));
+	io->free_iovec = iovec;
+	io->bytes_done = 0;
+	/* can only be fixed buffers, no need to do anything */
+	if (iov_iter_is_bvec(iter))
+		return;
+	if (!iovec) {
+		unsigned iov_off = 0;
+
+		io->s.iter.iov = io->s.fast_iov;
+		if (iter->iov != fast_iov) {
+			iov_off = iter->iov - fast_iov;
+			io->s.iter.iov += iov_off;
+		}
+		if (io->s.fast_iov != fast_iov)
+			memcpy(io->s.fast_iov + iov_off, fast_iov + iov_off,
+			       sizeof(struct iovec) * iter->nr_segs);
+	} else {
+		req->flags |= REQ_F_NEED_CLEANUP;
+	}
+}
+
+static int io_setup_async_rw(struct io_kiocb *req, const struct iovec *iovec,
+			     struct io_rw_state *s, bool force)
+{
+	if (!force && !io_op_defs[req->opcode].prep_async)
+		return 0;
+	if (!req_has_async_data(req)) {
+		struct io_async_rw *iorw;
+
+		if (io_alloc_async_data(req)) {
+			kfree(iovec);
+			return -ENOMEM;
+		}
+
+		io_req_map_rw(req, iovec, s->fast_iov, &s->iter);
+		iorw = req->async_data;
+		/* we've copied and mapped the iter, ensure state is saved */
+		iov_iter_save_state(&iorw->s.iter, &iorw->s.iter_state);
+	}
+	return 0;
+}
+
+static inline int io_rw_prep_async(struct io_kiocb *req, int rw)
+{
+	struct io_async_rw *iorw = req->async_data;
+	struct iovec *iov;
+	int ret;
+
+	/* submission path, ->uring_lock should already be taken */
+	ret = io_import_iovec(rw, req, &iov, &iorw->s, 0);
+	if (unlikely(ret < 0))
+		return ret;
+
+	iorw->bytes_done = 0;
+	iorw->free_iovec = iov;
+	if (iov)
+		req->flags |= REQ_F_NEED_CLEANUP;
+	return 0;
+}
+
+int io_readv_prep_async(struct io_kiocb *req)
+{
+	return io_rw_prep_async(req, READ);
+}
+
+int io_writev_prep_async(struct io_kiocb *req)
+{
+	return io_rw_prep_async(req, WRITE);
+}
+
+/*
+ * This is our waitqueue callback handler, registered through __folio_lock_async()
+ * when we initially tried to do the IO with the iocb armed our waitqueue.
+ * This gets called when the page is unlocked, and we generally expect that to
+ * happen when the page IO is completed and the page is now uptodate. This will
+ * queue a task_work based retry of the operation, attempting to copy the data
+ * again. If the latter fails because the page was NOT uptodate, then we will
+ * do a thread based blocking retry of the operation. That's the unexpected
+ * slow path.
+ */
+static int io_async_buf_func(struct wait_queue_entry *wait, unsigned mode,
+			     int sync, void *arg)
+{
+	struct wait_page_queue *wpq;
+	struct io_kiocb *req = wait->private;
+	struct io_rw *rw = io_kiocb_to_cmd(req);
+	struct wait_page_key *key = arg;
+
+	wpq = container_of(wait, struct wait_page_queue, wait);
+
+	if (!wake_page_match(wpq, key))
+		return 0;
+
+	rw->kiocb.ki_flags &= ~IOCB_WAITQ;
+	list_del_init(&wait->entry);
+	io_req_task_queue(req);
+	return 1;
+}
+
+/*
+ * This controls whether a given IO request should be armed for async page
+ * based retry. If we return false here, the request is handed to the async
+ * worker threads for retry. If we're doing buffered reads on a regular file,
+ * we prepare a private wait_page_queue entry and retry the operation. This
+ * will either succeed because the page is now uptodate and unlocked, or it
+ * will register a callback when the page is unlocked at IO completion. Through
+ * that callback, io_uring uses task_work to setup a retry of the operation.
+ * That retry will attempt the buffered read again. The retry will generally
+ * succeed, or in rare cases where it fails, we then fall back to using the
+ * async worker threads for a blocking retry.
+ */
+static bool io_rw_should_retry(struct io_kiocb *req)
+{
+	struct io_async_rw *io = req->async_data;
+	struct wait_page_queue *wait = &io->wpq;
+	struct io_rw *rw = io_kiocb_to_cmd(req);
+	struct kiocb *kiocb = &rw->kiocb;
+
+	/* never retry for NOWAIT, we just complete with -EAGAIN */
+	if (req->flags & REQ_F_NOWAIT)
+		return false;
+
+	/* Only for buffered IO */
+	if (kiocb->ki_flags & (IOCB_DIRECT | IOCB_HIPRI))
+		return false;
+
+	/*
+	 * just use poll if we can, and don't attempt if the fs doesn't
+	 * support callback based unlocks
+	 */
+	if (file_can_poll(req->file) || !(req->file->f_mode & FMODE_BUF_RASYNC))
+		return false;
+
+	wait->wait.func = io_async_buf_func;
+	wait->wait.private = req;
+	wait->wait.flags = 0;
+	INIT_LIST_HEAD(&wait->wait.entry);
+	kiocb->ki_flags |= IOCB_WAITQ;
+	kiocb->ki_flags &= ~IOCB_NOWAIT;
+	kiocb->ki_waitq = wait;
+	return true;
+}
+
+static inline int io_iter_do_read(struct io_rw *rw, struct iov_iter *iter)
+{
+	struct file *file = rw->kiocb.ki_filp;
+
+	if (likely(file->f_op->read_iter))
+		return call_read_iter(file, &rw->kiocb, iter);
+	else if (file->f_op->read)
+		return loop_rw_iter(READ, rw, iter);
+	else
+		return -EINVAL;
+}
+
+static bool need_read_all(struct io_kiocb *req)
+{
+	return req->flags & REQ_F_ISREG ||
+		S_ISBLK(file_inode(req->file)->i_mode);
+}
+
+static inline bool io_req_ffs_set(struct io_kiocb *req)
+{
+	return req->flags & REQ_F_FIXED_FILE;
+}
+
+static int io_rw_init_file(struct io_kiocb *req, fmode_t mode)
+{
+	struct io_rw *rw = io_kiocb_to_cmd(req);
+	struct kiocb *kiocb = &rw->kiocb;
+	struct io_ring_ctx *ctx = req->ctx;
+	struct file *file = req->file;
+	int ret;
+
+	if (unlikely(!file || !(file->f_mode & mode)))
+		return -EBADF;
+
+	if (!io_req_ffs_set(req))
+		req->flags |= io_file_get_flags(file) << REQ_F_SUPPORT_NOWAIT_BIT;
+
+	kiocb->ki_flags = iocb_flags(file);
+	ret = kiocb_set_rw_flags(kiocb, rw->flags);
+	if (unlikely(ret))
+		return ret;
+
+	/*
+	 * If the file is marked O_NONBLOCK, still allow retry for it if it
+	 * supports async. Otherwise it's impossible to use O_NONBLOCK files
+	 * reliably. If not, or it IOCB_NOWAIT is set, don't retry.
+	 */
+	if ((kiocb->ki_flags & IOCB_NOWAIT) ||
+	    ((file->f_flags & O_NONBLOCK) && !io_file_supports_nowait(req)))
+		req->flags |= REQ_F_NOWAIT;
+
+	if (ctx->flags & IORING_SETUP_IOPOLL) {
+		if (!(kiocb->ki_flags & IOCB_DIRECT) || !file->f_op->iopoll)
+			return -EOPNOTSUPP;
+
+		kiocb->private = NULL;
+		kiocb->ki_flags |= IOCB_HIPRI | IOCB_ALLOC_CACHE;
+		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;
+	}
+
+	return 0;
+}
+
+int io_read(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_rw *rw = io_kiocb_to_cmd(req);
+	struct io_rw_state __s, *s = &__s;
+	struct iovec *iovec;
+	struct kiocb *kiocb = &rw->kiocb;
+	bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
+	struct io_async_rw *io;
+	ssize_t ret, ret2;
+	loff_t *ppos;
+
+	if (!req_has_async_data(req)) {
+		ret = io_import_iovec(READ, req, &iovec, s, issue_flags);
+		if (unlikely(ret < 0))
+			return ret;
+	} else {
+		io = req->async_data;
+		s = &io->s;
+
+		/*
+		 * Safe and required to re-import if we're using provided
+		 * buffers, as we dropped the selected one before retry.
+		 */
+		if (io_do_buffer_select(req)) {
+			ret = io_import_iovec(READ, req, &iovec, s, issue_flags);
+			if (unlikely(ret < 0))
+				return ret;
+		}
+
+		/*
+		 * We come here from an earlier attempt, restore our state to
+		 * match in case it doesn't. It's cheap enough that we don't
+		 * need to make this conditional.
+		 */
+		iov_iter_restore(&s->iter, &s->iter_state);
+		iovec = NULL;
+	}
+	ret = io_rw_init_file(req, FMODE_READ);
+	if (unlikely(ret)) {
+		kfree(iovec);
+		return ret;
+	}
+	req->cqe.res = iov_iter_count(&s->iter);
+
+	if (force_nonblock) {
+		/* If the file doesn't support async, just async punt */
+		if (unlikely(!io_file_supports_nowait(req))) {
+			ret = io_setup_async_rw(req, iovec, s, true);
+			return ret ?: -EAGAIN;
+		}
+		kiocb->ki_flags |= IOCB_NOWAIT;
+	} else {
+		/* Ensure we clear previously set non-block flag */
+		kiocb->ki_flags &= ~IOCB_NOWAIT;
+	}
+
+	ppos = io_kiocb_update_pos(req);
+
+	ret = rw_verify_area(READ, req->file, ppos, req->cqe.res);
+	if (unlikely(ret)) {
+		kfree(iovec);
+		return ret;
+	}
+
+	ret = io_iter_do_read(rw, &s->iter);
+
+	if (ret == -EAGAIN || (req->flags & REQ_F_REISSUE)) {
+		req->flags &= ~REQ_F_REISSUE;
+		/* if we can poll, just do that */
+		if (req->opcode == IORING_OP_READ && file_can_poll(req->file))
+			return -EAGAIN;
+		/* IOPOLL retry should happen for io-wq threads */
+		if (!force_nonblock && !(req->ctx->flags & IORING_SETUP_IOPOLL))
+			goto done;
+		/* no retry on NONBLOCK nor RWF_NOWAIT */
+		if (req->flags & REQ_F_NOWAIT)
+			goto done;
+		ret = 0;
+	} else if (ret == -EIOCBQUEUED) {
+		goto out_free;
+	} else if (ret == req->cqe.res || ret <= 0 || !force_nonblock ||
+		   (req->flags & REQ_F_NOWAIT) || !need_read_all(req)) {
+		/* read all, failed, already did sync or don't want to retry */
+		goto done;
+	}
+
+	/*
+	 * Don't depend on the iter state matching what was consumed, or being
+	 * untouched in case of error. Restore it and we'll advance it
+	 * manually if we need to.
+	 */
+	iov_iter_restore(&s->iter, &s->iter_state);
+
+	ret2 = io_setup_async_rw(req, iovec, s, true);
+	if (ret2)
+		return ret2;
+
+	iovec = NULL;
+	io = req->async_data;
+	s = &io->s;
+	/*
+	 * Now use our persistent iterator and state, if we aren't already.
+	 * We've restored and mapped the iter to match.
+	 */
+
+	do {
+		/*
+		 * We end up here because of a partial read, either from
+		 * above or inside this loop. Advance the iter by the bytes
+		 * that were consumed.
+		 */
+		iov_iter_advance(&s->iter, ret);
+		if (!iov_iter_count(&s->iter))
+			break;
+		io->bytes_done += ret;
+		iov_iter_save_state(&s->iter, &s->iter_state);
+
+		/* if we can retry, do so with the callbacks armed */
+		if (!io_rw_should_retry(req)) {
+			kiocb->ki_flags &= ~IOCB_WAITQ;
+			return -EAGAIN;
+		}
+
+		/*
+		 * Now retry read with the IOCB_WAITQ parts set in the iocb. If
+		 * we get -EIOCBQUEUED, then we'll get a notification when the
+		 * desired page gets unlocked. We can also get a partial read
+		 * here, and if we do, then just retry at the new offset.
+		 */
+		ret = io_iter_do_read(rw, &s->iter);
+		if (ret == -EIOCBQUEUED)
+			return IOU_ISSUE_SKIP_COMPLETE;
+		/* we got some bytes, but not all. retry. */
+		kiocb->ki_flags &= ~IOCB_WAITQ;
+		iov_iter_restore(&s->iter, &s->iter_state);
+	} while (ret > 0);
+done:
+	kiocb_done(req, ret, issue_flags);
+out_free:
+	/* it's faster to check here then delegate to kfree */
+	if (iovec)
+		kfree(iovec);
+	return IOU_ISSUE_SKIP_COMPLETE;
+}
+
+int io_write(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_rw *rw = io_kiocb_to_cmd(req);
+	struct io_rw_state __s, *s = &__s;
+	struct iovec *iovec;
+	struct kiocb *kiocb = &rw->kiocb;
+	bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
+	ssize_t ret, ret2;
+	loff_t *ppos;
+
+	if (!req_has_async_data(req)) {
+		ret = io_import_iovec(WRITE, req, &iovec, s, issue_flags);
+		if (unlikely(ret < 0))
+			return ret;
+	} else {
+		struct io_async_rw *io = req->async_data;
+
+		s = &io->s;
+		iov_iter_restore(&s->iter, &s->iter_state);
+		iovec = NULL;
+	}
+	ret = io_rw_init_file(req, FMODE_WRITE);
+	if (unlikely(ret)) {
+		kfree(iovec);
+		return ret;
+	}
+	req->cqe.res = iov_iter_count(&s->iter);
+
+	if (force_nonblock) {
+		/* If the file doesn't support async, just async punt */
+		if (unlikely(!io_file_supports_nowait(req)))
+			goto copy_iov;
+
+		/* file path doesn't support NOWAIT for non-direct_IO */
+		if (force_nonblock && !(kiocb->ki_flags & IOCB_DIRECT) &&
+		    (req->flags & REQ_F_ISREG))
+			goto copy_iov;
+
+		kiocb->ki_flags |= IOCB_NOWAIT;
+	} else {
+		/* Ensure we clear previously set non-block flag */
+		kiocb->ki_flags &= ~IOCB_NOWAIT;
+	}
+
+	ppos = io_kiocb_update_pos(req);
+
+	ret = rw_verify_area(WRITE, req->file, ppos, req->cqe.res);
+	if (unlikely(ret))
+		goto out_free;
+
+	/*
+	 * Open-code file_start_write here to grab freeze protection,
+	 * which will be released by another thread in
+	 * io_complete_rw().  Fool lockdep by telling it the lock got
+	 * released so that it doesn't complain about the held lock when
+	 * we return to userspace.
+	 */
+	if (req->flags & REQ_F_ISREG) {
+		sb_start_write(file_inode(req->file)->i_sb);
+		__sb_writers_release(file_inode(req->file)->i_sb,
+					SB_FREEZE_WRITE);
+	}
+	kiocb->ki_flags |= IOCB_WRITE;
+
+	if (likely(req->file->f_op->write_iter))
+		ret2 = call_write_iter(req->file, kiocb, &s->iter);
+	else if (req->file->f_op->write)
+		ret2 = loop_rw_iter(WRITE, rw, &s->iter);
+	else
+		ret2 = -EINVAL;
+
+	if (req->flags & REQ_F_REISSUE) {
+		req->flags &= ~REQ_F_REISSUE;
+		ret2 = -EAGAIN;
+	}
+
+	/*
+	 * Raw bdev writes will return -EOPNOTSUPP for IOCB_NOWAIT. Just
+	 * retry them without IOCB_NOWAIT.
+	 */
+	if (ret2 == -EOPNOTSUPP && (kiocb->ki_flags & IOCB_NOWAIT))
+		ret2 = -EAGAIN;
+	/* no retry on NONBLOCK nor RWF_NOWAIT */
+	if (ret2 == -EAGAIN && (req->flags & REQ_F_NOWAIT))
+		goto done;
+	if (!force_nonblock || ret2 != -EAGAIN) {
+		/* IOPOLL retry should happen for io-wq threads */
+		if (ret2 == -EAGAIN && (req->ctx->flags & IORING_SETUP_IOPOLL))
+			goto copy_iov;
+done:
+		kiocb_done(req, ret2, issue_flags);
+		ret = IOU_ISSUE_SKIP_COMPLETE;
+	} else {
+copy_iov:
+		iov_iter_restore(&s->iter, &s->iter_state);
+		ret = io_setup_async_rw(req, iovec, s, false);
+		return ret ?: -EAGAIN;
+	}
+out_free:
+	/* it's reportedly faster than delegating the null check to kfree() */
+	if (iovec)
+		kfree(iovec);
+	return ret;
+}
+
+static void io_cqring_ev_posted_iopoll(struct io_ring_ctx *ctx)
+{
+	if (unlikely(ctx->off_timeout_used || ctx->drain_active ||
+		     ctx->has_evfd))
+		__io_commit_cqring_flush(ctx);
+
+	if (ctx->flags & IORING_SETUP_SQPOLL)
+		io_cqring_wake(ctx);
+}
+
+int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin)
+{
+	struct io_wq_work_node *pos, *start, *prev;
+	unsigned int poll_flags = BLK_POLL_NOSLEEP;
+	DEFINE_IO_COMP_BATCH(iob);
+	int nr_events = 0;
+
+	/*
+	 * Only spin for completions if we don't have multiple devices hanging
+	 * off our complete list.
+	 */
+	if (ctx->poll_multi_queue || force_nonspin)
+		poll_flags |= BLK_POLL_ONESHOT;
+
+	wq_list_for_each(pos, start, &ctx->iopoll_list) {
+		struct io_kiocb *req = container_of(pos, struct io_kiocb, comp_list);
+		struct io_rw *rw = io_kiocb_to_cmd(req);
+		int ret;
+
+		/*
+		 * 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))
+			break;
+
+		ret = rw->kiocb.ki_filp->f_op->iopoll(&rw->kiocb, &iob, poll_flags);
+		if (unlikely(ret < 0))
+			return ret;
+		else if (ret)
+			poll_flags |= BLK_POLL_ONESHOT;
+
+		/* iopoll may have completed current req */
+		if (!rq_list_empty(iob.req_list) ||
+		    READ_ONCE(req->iopoll_completed))
+			break;
+	}
+
+	if (!rq_list_empty(iob.req_list))
+		iob.complete(&iob);
+	else if (!pos)
+		return 0;
+
+	prev = start;
+	wq_list_for_each_resume(pos, prev) {
+		struct io_kiocb *req = container_of(pos, struct io_kiocb, comp_list);
+
+		/* order with io_complete_rw_iopoll(), e.g. ->result updates */
+		if (!smp_load_acquire(&req->iopoll_completed))
+			break;
+		nr_events++;
+		if (unlikely(req->flags & REQ_F_CQE_SKIP))
+			continue;
+
+		req->cqe.flags = io_put_kbuf(req, 0);
+		__io_fill_cqe_req(req->ctx, req);
+	}
+
+	if (unlikely(!nr_events))
+		return 0;
+
+	io_commit_cqring(ctx);
+	io_cqring_ev_posted_iopoll(ctx);
+	pos = start ? start->next : ctx->iopoll_list.first;
+	wq_list_cut(&ctx->iopoll_list, prev, start);
+	io_free_batch_list(ctx, pos);
+	return nr_events;
+}