Between the moment when generic_make_request() is first called on a bio, and when bio_endio() finally gets past bio_remaining_done(), a bio might have chained children, and might get ->bi_status set asynchronously.
So during this time it is not safe to set it to zero. It *is* safe to set it to any other error status as for most purposes, one error is as good as another. This patch is untested and RFC only. It identifies a number of possible problem areas in dm and often suggests fixes. Please don't apply without careful review. Reviewed-by: Nobody yet. Signed-off-by: NeilBrown <ne...@suse.com> --- drivers/md/dm-bio-prison-v1.c | 3 ++- drivers/md/dm-bufio.c | 6 ++++-- drivers/md/dm-crypt.c | 3 ++- drivers/md/dm-mpath.c | 3 +++ drivers/md/dm-thin.c | 3 ++- drivers/md/dm-verity-target.c | 3 ++- drivers/md/dm-zoned-target.c | 3 ++- 7 files changed, 17 insertions(+), 7 deletions(-) diff --git a/drivers/md/dm-bio-prison-v1.c b/drivers/md/dm-bio-prison-v1.c index 874841f0fc83..68cb4fe98e9f 100644 --- a/drivers/md/dm-bio-prison-v1.c +++ b/drivers/md/dm-bio-prison-v1.c @@ -238,7 +238,8 @@ void dm_cell_error(struct dm_bio_prison *prison, dm_cell_release(prison, cell, &bios); while ((bio = bio_list_pop(&bios))) { - bio->bi_status = error; + if (error) + bio->bi_status = error; bio_endio(bio); } } diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c index 414c9af54ded..80131e098650 100644 --- a/drivers/md/dm-bufio.c +++ b/drivers/md/dm-bufio.c @@ -565,7 +565,8 @@ static void dmio_complete(unsigned long error, void *context) { struct dm_buffer *b = context; - b->bio.bi_status = error ? BLK_STS_IOERR : 0; + if (error) + b->bio.bi_status = BLK_STS_IOERR; b->bio.bi_end_io(&b->bio); } @@ -614,7 +615,8 @@ static void inline_endio(struct bio *bio) */ bio_reset(bio); - bio->bi_status = status; + if (status) + bio->bi_status = status; end_fn(bio); } diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c index 8168f737590e..3e7db4a1093e 100644 --- a/drivers/md/dm-crypt.c +++ b/drivers/md/dm-crypt.c @@ -1488,7 +1488,8 @@ static void crypt_dec_pending(struct dm_crypt_io *io) else kfree(io->integrity_metadata); - base_bio->bi_status = error; + if (error) + base_bio->bi_status = error; bio_endio(base_bio); } diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c index 7d3e572072f5..6f793d7d29f0 100644 --- a/drivers/md/dm-mpath.c +++ b/drivers/md/dm-mpath.c @@ -651,6 +651,9 @@ static int __multipath_map_bio(struct multipath *m, struct bio *bio, mpio->pgpath = pgpath; + /* FIXME If the bio was chained, this could + * over-write an error... is that possible? + */ bio->bi_status = 0; bio_set_dev(bio, pgpath->path.dev->bdev); bio->bi_opf |= REQ_FAILFAST_TRANSPORT; diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index 629c555890c1..16d4c386cc56 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -563,7 +563,8 @@ static void error_bio_list(struct bio_list *bios, blk_status_t error) struct bio *bio; while ((bio = bio_list_pop(bios))) { - bio->bi_status = error; + if (error) + bio->bi_status = error; bio_endio(bio); } } diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c index aedb8222836b..86a1d501d915 100644 --- a/drivers/md/dm-verity-target.c +++ b/drivers/md/dm-verity-target.c @@ -503,7 +503,8 @@ static void verity_finish_io(struct dm_verity_io *io, blk_status_t status) struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size); bio->bi_end_io = io->orig_bi_end_io; - bio->bi_status = status; + if (status) + bio->bi_status = status; verity_fec_finish_io(io); diff --git a/drivers/md/dm-zoned-target.c b/drivers/md/dm-zoned-target.c index caff02caf083..cfdacaf79492 100644 --- a/drivers/md/dm-zoned-target.c +++ b/drivers/md/dm-zoned-target.c @@ -637,7 +637,8 @@ static int dmz_end_io(struct dm_target *ti, struct bio *bio, blk_status_t *error return DM_ENDIO_INCOMPLETE; /* Done */ - bio->bi_status = bioctx->status; + if (bioctx->status) + bio->bi_status = bioctx->status; if (bioctx->zone) { struct dm_zone *zone = bioctx->zone; -- 2.14.0.rc0.dirty
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