From 54caccb3657e3960d8f5d57ab8e867028325d131 Mon Sep 17 00:00:00 2001 From: Fabian Ebner Date: Thu, 29 Jul 2021 11:10:29 +0200 Subject: [PATCH] block/io_uring: resubmit when result is -EAGAIN Linux SCSI can throw spurious -EAGAIN in some corner cases in its completion path, which will end up being the result in the completed io_uring request. Resubmitting such requests should allow block jobs to complete, even if such spurious errors are encountered. Co-authored-by: Stefan Hajnoczi Reviewed-by: Stefano Garzarella Signed-off-by: Fabian Ebner Message-id: 20210729091029.65369-1-f.ebner@proxmox.com Signed-off-by: Stefan Hajnoczi --- block/io_uring.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/block/io_uring.c b/block/io_uring.c index 00a3ee9fb852..dfa475cc8746 100644 --- a/block/io_uring.c +++ b/block/io_uring.c @@ -165,7 +165,21 @@ static void luring_process_completions(LuringState *s) total_bytes = ret + luringcb->total_read; if (ret < 0) { - if (ret == -EINTR) { + /* + * Only writev/readv/fsync requests on regular files or host block + * devices are submitted. Therefore -EAGAIN is not expected but it's + * known to happen sometimes with Linux SCSI. Submit again and hope + * the request completes successfully. + * + * For more information, see: + * https://lore.kernel.org/io-uring/20210727165811.284510-3-axboe@kernel.dk/T/#u + * + * If the code is changed to submit other types of requests in the + * future, then this workaround may need to be extended to deal with + * genuine -EAGAIN results that should not be resubmitted + * immediately. + */ + if (ret == -EINTR || ret == -EAGAIN) { luring_resubmit(s, luringcb); continue; }