From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: "Martin K. Petersen" , Seunguk Shin , Jens Axboe , Kent Overstreet , Kamal Mostafa Subject: [PATCH 3.19.y-ckt 045/130] block: Do a full clone when splitting discard bios Date: Thu, 27 Aug 2015 15:10:36 -0700 Message-Id: <1440713521-5906-46-git-send-email-kamal@canonical.com> In-Reply-To: <1440713521-5906-1-git-send-email-kamal@canonical.com> References: <1440713521-5906-1-git-send-email-kamal@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.19.8-ckt6 -stable review patch. If anyone has any objections, please let me know. ------------------ From: "Martin K. Petersen" commit f3f5da624e0a891c34d8cd513c57f1d9b0c7dadc upstream. 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 Reviewed-by: Christoph Hellwig Signed-off-by: Jens Axboe Signed-off-by: Kamal Mostafa --- block/bio.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/block/bio.c b/block/bio.c index 471d738..dae3483 100644 --- a/block/bio.c +++ b/block/bio.c @@ -1858,8 +1858,9 @@ EXPORT_SYMBOL(bio_endio_nodec); * 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) @@ -1869,7 +1870,15 @@ 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; -- 1.9.1