From: Martin K. Petersen Date: Wed, 22 Jul 2015 11:57:12 +0000 (-0400) Subject: block: Do a full clone when splitting discard bios X-Git-Tag: v4.2~144^2 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=f3f5da624e0a891c34d8cd513c57f1d9b0c7dadc;p=platform%2Fkernel%2Flinux-amlogic.git block: Do a full clone when splitting discard bios This fixes a data corruption bug when using discard on top of MD linear, raid0 and raid10 personalities. Commit 20d0189b1012 "block: Introduce new bio_split()" permits sharing the bio_vec between the two resulting bios. That is fine for read/write requests where the bio_vec is immutable. For discards, however, we need to be able to attach a payload and update the bio_vec so the page can get mapped to a scatterlist entry. Therefore the bio_vec can not be shared when splitting discards and we must do a full clone. Signed-off-by: Martin K. Petersen Reported-by: Seunguk Shin Tested-by: Seunguk Shin Cc: Seunguk Shin Cc: Jens Axboe Cc: Kent Overstreet Cc: # v3.14+ Reviewed-by: Christoph Hellwig Signed-off-by: Jens Axboe --- diff --git a/block/bio.c b/block/bio.c index b671a0f..d6e5ba3 100644 --- a/block/bio.c +++ b/block/bio.c @@ -1831,8 +1831,9 @@ EXPORT_SYMBOL(bio_endio); * Allocates and returns a new bio which represents @sectors from the start of * @bio, and updates @bio to represent the remaining sectors. * - * The newly allocated bio will point to @bio's bi_io_vec; it is the caller's - * responsibility to ensure that @bio is not freed before the split. + * Unless this is a discard request the newly allocated bio will point + * to @bio's bi_io_vec; it is the caller's responsibility to ensure that + * @bio is not freed before the split. */ struct bio *bio_split(struct bio *bio, int sectors, gfp_t gfp, struct bio_set *bs) @@ -1842,7 +1843,15 @@ struct bio *bio_split(struct bio *bio, int sectors, BUG_ON(sectors <= 0); BUG_ON(sectors >= bio_sectors(bio)); - split = bio_clone_fast(bio, gfp, bs); + /* + * Discards need a mutable bio_vec to accommodate the payload + * required by the DSM TRIM and UNMAP commands. + */ + if (bio->bi_rw & REQ_DISCARD) + split = bio_clone_bioset(bio, gfp, bs); + else + split = bio_clone_fast(bio, gfp, bs); + if (!split) return NULL;