[RESEND PATCH v9 11/14] io_uring: Add support for async buffered writes

Stefan Roesch
2022-06-23T19:09:32Z

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>
---
fs/io_uring.c | 29 ++++++++++++++++++++++++-----
1 file changed, 24 insertions(+), 5 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 3aab4182fd89..22a0bb8c5fe5 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4311,7 +4311,7 @@ static inline int io_iter_do_read(struct io_kiocb *req, 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);
@@ -4440,7 +4440,7 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
} 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)) {
+ (req->flags & REQ_F_NOWAIT) || !need_complete_io(req)) {
/* read all, failed, already did sync or don't want to retry */
goto done;
}
@@ -4536,9 +4536,10 @@ static 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;
@@ -4592,6 +4593,24 @@ static 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:
kiocb_done(req, ret2, issue_flags);
} else {
--
2.30.2