From 62ce0782bbacd32ec10292b9bdd127330e9b6968 Mon Sep 17 00:00:00 2001 From: Li Nan Date: Thu, 19 Sep 2024 14:30:48 +0800 Subject: [PATCH] md: ensure child flush IO does not affect origin bio->bi_status When a flush is issued to an RAID array, a child flush IO is created and issued for each member disk in the RAID array. Since commit b75197e86e6d ("md: Remove flush handling"), each child flush IO has been chained with the original bio. As a result, the failure of any child IO could modify the bi_status of the original bio, potentially impacting the upper-layer filesystem. Fix the issue by preventing child flush IO from altering the original bio->bi_status as before. However, this design introduces a known issue: in the event of a power failure, if a flush IO on a member disk fails, the upper layers may not be informed. This issue is not easy to fix and will not be addressed for the time being in this issue. Fixes: b75197e86e6d ("md: Remove flush handling") Signed-off-by: Li Nan Reviewed-by: Yu Kuai Link: https://lore.kernel.org/r/20240919063048.2887579-1-linan666@huaweicloud.com Signed-off-by: Song Liu --- drivers/md/md.c | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index 179ee4afe937..67108c397c5a 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -546,6 +546,26 @@ static int mddev_set_closing_and_sync_blockdev(struct mddev *mddev, int opener_n return 0; } +/* + * The only difference from bio_chain_endio() is that the current + * bi_status of bio does not affect the bi_status of parent. + */ +static void md_end_flush(struct bio *bio) +{ + struct bio *parent = bio->bi_private; + + /* + * If any flush io error before the power failure, + * disk data may be lost. + */ + if (bio->bi_status) + pr_err("md: %pg flush io error %d\n", bio->bi_bdev, + blk_status_to_errno(bio->bi_status)); + + bio_put(bio); + bio_endio(parent); +} + bool md_flush_request(struct mddev *mddev, struct bio *bio) { struct md_rdev *rdev; @@ -565,7 +585,9 @@ bool md_flush_request(struct mddev *mddev, struct bio *bio) new = bio_alloc_bioset(rdev->bdev, 0, REQ_OP_WRITE | REQ_PREFLUSH, GFP_NOIO, &mddev->bio_set); - bio_chain(new, bio); + new->bi_private = bio; + new->bi_end_io = md_end_flush; + bio_inc_remaining(bio); submit_bio(new); }