[PATCH 03/15] io_uring: catch -EIO from buffered issue request failure

Jens Axboe
2020-06-18T14:46:19Z

-EIO bubbles up like -EAGAIN if we fail to allocate a request at the
lower level. Play it safe and treat it like -EAGAIN in terms of sync
retry, to avoid passing back an errant -EIO.

Catch some of these early for block based file, as non-mq devices
generally do not support NOWAIT. That saves us some overhead by
not first trying, then retrying from async context. We can go straight
to async punt instead.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
fs/io_uring.c | 28 +++++++++++++++++++++++-----
1 file changed, 23 insertions(+), 5 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index ca78dd7c79da..2e257c5a1866 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2088,6 +2088,15 @@ static struct file *__io_file_get(struct io_submit_state *state, int fd)
return state->file;
}

+static bool io_bdev_nowait(struct block_device *bdev)
+{
+#ifdef CONFIG_BLOCK
+ return !bdev || queue_is_mq(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
@@ -2097,10 +2106,19 @@ static bool io_file_supports_async(struct file *file, int rw)
{
umode_t mode = file_inode(file)->i_mode;

- if (S_ISBLK(mode) || S_ISCHR(mode) || S_ISSOCK(mode))
- return true;
- if (S_ISREG(mode) && file->f_op != &io_uring_fops)
+ if (S_ISBLK(mode)) {
+ if (io_bdev_nowait(file->f_inode->i_bdev))
+ return true;
+ return false;
+ }
+ if (S_ISCHR(mode) || 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)
@@ -2650,7 +2668,7 @@ static int io_read(struct io_kiocb *req, bool force_nonblock)
iov_count = iov_iter_count(&iter);
ret = rw_verify_area(READ, req->file, &kiocb->ki_pos, iov_count);
if (!ret) {
- ssize_t ret2;
+ ssize_t ret2 = 0;

if (req->file->f_op->read_iter)
ret2 = call_read_iter(req->file, kiocb, &iter);
@@ -2658,7 +2676,7 @@ static int io_read(struct io_kiocb *req, bool force_nonblock)
ret2 = loop_rw_iter(READ, req->file, kiocb, &iter);

/* Catch -EAGAIN return for forced non-blocking submission */
- if (!force_nonblock || ret2 != -EAGAIN) {
+ if (!force_nonblock || (ret2 != -EAGAIN && ret2 != -EIO)) {
kiocb_done(kiocb, ret2);
} else {
copy_iov:
--
2.27.0