From be6a166fde652589761cf70471bcde623e9bd72a Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Wed, 6 Jul 2022 09:03:41 +0100 Subject: [PATCH] block/io_uring: clarify that short reads can happen 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 Based-on: <20220630010137.2518851-1-dominique.martinet@atmark-techno.com> Signed-off-by: Stefan Hajnoczi Reviewed-by: Stefano Garzarella Message-id: 20220706080341.1206476-1-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi --- block/io_uring.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/block/io_uring.c b/block/io_uring.c index b238661740..f8a19fd97f 100644 --- a/block/io_uring.c +++ b/block/io_uring.c @@ -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)