diff options
authorJens Axboe <>2020-01-07 13:08:56 -0700
committerJens Axboe <>2020-01-07 13:08:56 -0700
commiteacc6dfaea963ef61540abb31ad7829be5eff284 (patch)
parentfd1c4bc6e9b34a5e4fe7a3130a49380ef9d7037c (diff)
io_uring: remove punt of short reads to async contextio_uring-5.5-2020-01-10
We currently punt any short read on a regular file to async context, but this fails if the short read is due to running into EOF. This is especially problematic since we only do the single prep for commands now, as we don't reset kiocb->ki_pos. This can result in a 4k read on a 1k file returning zero, as we detect the short read and then retry from async context. At the time of retry, the position is now 1k, and we end up reading nothing, and hence return 0. Instead of trying to patch around the fact that short reads can be legitimate and won't succeed in case of retry, remove the logic to punt a short read to async context. Simply return it. Signed-off-by: Jens Axboe <>
1 files changed, 0 insertions, 12 deletions
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 562e3a1a1bf9..38b54051facd 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1863,18 +1863,6 @@ static int io_read(struct io_kiocb *req, struct io_kiocb **nxt,
ret2 = loop_rw_iter(READ, req->file, kiocb, &iter);
- /*
- * In case of a short read, punt to async. This can happen
- * if we have data partially cached. Alternatively we can
- * return the short read, in which case the application will
- * need to issue another SQE and wait for it. That SQE will
- * need async punt anyway, so it's more efficient to do it
- * here.
- */
- if (force_nonblock && !(req->flags & REQ_F_NOWAIT) &&
- (req->flags & REQ_F_ISREG) &&
- ret2 > 0 && ret2 < io_size)
- ret2 = -EAGAIN;
/* Catch -EAGAIN return for forced non-blocking submission */
if (!force_nonblock || ret2 != -EAGAIN) {
kiocb_done(kiocb, ret2, nxt, req->in_async);