Patch "block: fix partial zone append completion handling in req_bio_endio()" has been added to the 6.1-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    block: fix partial zone append completion handling in req_bio_endio()

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     block-fix-partial-zone-append-completion-handling-in.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 47fb8021b12dd28882142c16a943950572d5a2ec
Author: Damien Le Moal <dlemoal@xxxxxxxxxx>
Date:   Wed Jan 10 18:29:42 2024 +0900

    block: fix partial zone append completion handling in req_bio_endio()
    
    [ Upstream commit 748dc0b65ec2b4b7b3dbd7befcc4a54fdcac7988 ]
    
    Partial completions of zone append request is not allowed but if a zone
    append completion indicates a number of completed bytes different from
    the original BIO size, only the BIO status is set to error. This leads
    to bio_advance() not setting the BIO size to 0 and thus to not call
    bio_endio() at the end of req_bio_endio().
    
    Make sure a partially completed zone append is failed and completed
    immediately by forcing the completed number of bytes (nbytes) to be
    equal to the BIO size, thus ensuring that bio_endio() is called.
    
    Fixes: 297db731847e ("block: fix req_bio_endio append error handling")
    Cc: stable@xxxxxxxxxxxxxxx
    Signed-off-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
    Reviewed-by: Christoph Hellwig <hch@xxxxxx>
    Reviewed-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
    Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
    Link: https://lore.kernel.org/r/20240110092942.442334-1-dlemoal@xxxxxxxxxx
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index c07e5eebcbd8..7ed6b9469f97 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -747,11 +747,16 @@ static void req_bio_endio(struct request *rq, struct bio *bio,
 		/*
 		 * Partial zone append completions cannot be supported as the
 		 * BIO fragments may end up not being written sequentially.
+		 * For such case, force the completed nbytes to be equal to
+		 * the BIO size so that bio_advance() sets the BIO remaining
+		 * size to 0 and we end up calling bio_endio() before returning.
 		 */
-		if (bio->bi_iter.bi_size != nbytes)
+		if (bio->bi_iter.bi_size != nbytes) {
 			bio->bi_status = BLK_STS_IOERR;
-		else
+			nbytes = bio->bi_iter.bi_size;
+		} else {
 			bio->bi_iter.bi_sector = rq->__sector;
+		}
 	}
 
 	bio_advance(bio, nbytes);