From: Ming Lei ming.lei@redhat.com
commit c8156fc77d0796ba2618936dbb3084e769e916c1 upstream.
Unit of 'chunk_size' is byte, instead of sector, so fix it by setting the queue_limits' max_discard_sectors to rs->md.chunk_sectors. Also, rename chunk_size to chunk_size_bytes.
Without this fix, too big max_discard_sectors is applied on the request queue of dm-raid, finally raid code has to split the bio again.
This re-split done by raid causes the following nested clone_endio:
1) one big bio 'A' is submitted to dm queue, and served as the original bio
2) one new bio 'B' is cloned from the original bio 'A', and .map() is run on this bio of 'B', and B's original bio points to 'A'
3) raid code sees that 'B' is too big, and split 'B' and re-submit the remainded part of 'B' to dm-raid queue via generic_make_request().
4) now dm will handle 'B' as new original bio, then allocate a new clone bio of 'C' and run .map() on 'C'. Meantime C's original bio points to 'B'.
5) suppose now 'C' is completed by raid directly, then the following clone_endio() is called recursively:
clone_endio(C) ->clone_endio(B) #B is original bio of 'C' ->bio_endio(A)
'A' can be big enough to make hundreds of nested clone_endio(), then stack can be corrupted easily.
Fixes: 61697a6abd24a ("dm: eliminate 'split_discard_bios' flag from DM target interface") Cc: stable@vger.kernel.org Signed-off-by: Ming Lei ming.lei@redhat.com Signed-off-by: Mike Snitzer snitzer@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/md/dm-raid.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)
--- a/drivers/md/dm-raid.c +++ b/drivers/md/dm-raid.c @@ -3738,18 +3738,18 @@ static int raid_iterate_devices(struct d static void raid_io_hints(struct dm_target *ti, struct queue_limits *limits) { struct raid_set *rs = ti->private; - unsigned int chunk_size = to_bytes(rs->md.chunk_sectors); + unsigned int chunk_size_bytes = to_bytes(rs->md.chunk_sectors);
- blk_limits_io_min(limits, chunk_size); - blk_limits_io_opt(limits, chunk_size * mddev_data_stripes(rs)); + blk_limits_io_min(limits, chunk_size_bytes); + blk_limits_io_opt(limits, chunk_size_bytes * mddev_data_stripes(rs));
/* * RAID1 and RAID10 personalities require bio splitting, * RAID0/4/5/6 don't and process large discard bios properly. */ if (rs_is_raid1(rs) || rs_is_raid10(rs)) { - limits->discard_granularity = chunk_size; - limits->max_discard_sectors = chunk_size; + limits->discard_granularity = chunk_size_bytes; + limits->max_discard_sectors = rs->md.chunk_sectors; } }