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block/io_uring: clarify that short reads can happen

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Jens Axboe has confirmed that short reads are rare but can happen:
https://lore.kernel.org/io-uring/YsU%2FCGkl9ZXUI+Tj@stefanha-x1.localdomain/T/#m729963dc577d709b709c191922e98ec79d7eef54

The luring_resubmit_short_read() comment claimed they were only due to a
specific io_uring bug that was fixed in Linux commit 9d93a3f5a0c
("io_uring: punt short reads to async context"), which is wrong.
Dominique Martinet found that a btrfs bug also causes short reads. There
may be more kernel code paths that result in short reads.

Let's consider short reads fair game.

Cc: Dominique Martinet <dominique.martinet@atmark-techno.com>
Based-on: <20220630010137.2518851-1-dominique.martinet@atmark-techno.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20220706080341.1206476-1-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2022-07-06 09:03:41 +01:00
parent c06fc7ce14
commit be6a166fde
1 changed files with 2 additions and 6 deletions
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8
block/io_uring.c
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@ -73,12 +73,8 @@ static void luring_resubmit(LuringState *s, LuringAIOCB *luringcb)
/**
* luring_resubmit_short_read:
*
* Before Linux commit 9d93a3f5a0c ("io_uring: punt short reads to async
* context") a buffered I/O request with the start of the file range in the
* page cache could result in a short read. Applications need to resubmit the
* remaining read request.
*
* This is a slow path but recent kernels never take it.
* Short reads are rare but may occur. The remaining read request needs to be
* resubmitted.
*/
static void luring_resubmit_short_read(LuringState *s, LuringAIOCB *luringcb,
int nread)