io_uring: Add support for async buffered writes

This enables the async buffered writes for the filesystems that support
async buffered writes in io-uring. Buffered writes are enabled for
blocks that are already in the page cache or can be acquired with noio.

Signed-off-by: Stefan Roesch <shr@fb.com>
Link: https://lore.kernel.org/r/20220616212221.2024518-12-shr@fb.com
[axboe: adapt to 5.20 branch]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/rw.c b/io_uring/rw.c
index c50a0d66d67a6697788989f659c090642b989616..4d4ca6389876b193edc3eef503d94bbeb5e28bf2 100644 (file)
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -641,7 +641,7 @@ static inline int io_iter_do_read(struct io_rw *rw, struct iov_iter *iter)
                return -EINVAL;
 }
 
-static bool need_read_all(struct io_kiocb *req)
+static bool need_complete_io(struct io_kiocb *req)
 {
        return req->flags & REQ_F_ISREG ||
                S_ISBLK(file_inode(req->file)->i_mode);
@@ -775,7 +775,7 @@ int io_read(struct io_kiocb *req, unsigned int issue_flags)
                        kfree(iovec);
                return IOU_ISSUE_SKIP_COMPLETE;
        } else if (ret == req->cqe.res || ret <= 0 || !force_nonblock ||
-                  (req->flags & REQ_F_NOWAIT) || !need_read_all(req)) {
+                  (req->flags & REQ_F_NOWAIT) || !need_complete_io(req)) {
                /* read all, failed, already did sync or don't want to retry */
                goto done;
        }
@@ -870,9 +870,10 @@ int io_write(struct io_kiocb *req, unsigned int issue_flags)
                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))
+               /* File path supports NOWAIT for non-direct_IO only for block devices. */
+               if (!(kiocb->ki_flags & IOCB_DIRECT) &&
+                       !(kiocb->ki_filp->f_mode & FMODE_BUF_WASYNC) &&
+                       (req->flags & REQ_F_ISREG))
                        goto copy_iov;
 
                kiocb->ki_flags |= IOCB_NOWAIT;
@@ -928,6 +929,24 @@ int io_write(struct io_kiocb *req, unsigned int issue_flags)
                /* IOPOLL retry should happen for io-wq threads */
                if (ret2 == -EAGAIN && (req->ctx->flags & IORING_SETUP_IOPOLL))
                        goto copy_iov;
+
+               if (ret2 != req->cqe.res && ret2 >= 0 && need_complete_io(req)) {
+                       struct io_async_rw *rw;
+
+                       /* This is a partial write. The file pos has already been
+                        * updated, setup the async struct to complete the request
+                        * in the worker. Also update bytes_done to account for
+                        * the bytes already written.
+                        */
+                       iov_iter_save_state(&s->iter, &s->iter_state);
+                       ret = io_setup_async_rw(req, iovec, s, true);
+
+                       rw = req->async_data;
+                       if (rw)
+                               rw->bytes_done += ret2;
+
+                       return ret ? ret : -EAGAIN;
+               }
 done:
                ret = kiocb_done(req, ret2, issue_flags);
        } else {