diff options
authorJoe Thornber <ejt@redhat.com>2015-05-29 14:52:51 +0100
committerMike Snitzer <snitzer@redhat.com>2015-05-29 13:41:16 -0400
commit1c220c69ce0dcc0f234a9f263ad9c0864f971852 (patch)
parent15b94a690470038aa08247eedbebbe7e2218d5ee (diff)
dm: fix casting bug in dm_merge_bvec()
dm_merge_bvec() was originally added in f6fccb ("dm: introduce merge_bvec_fn"). In that commit a value in sectors is converted to bytes using << 9, and then assigned to an int. This code made assumptions about the value of BIO_MAX_SECTORS. A later commit 148e51 ("dm: improve documentation and code clarity in dm_merge_bvec") was meant to have no functional change but it removed the use of BIO_MAX_SECTORS in favor of using queue_max_sectors(). At this point the cast from sector_t to int resulted in a zero value. The fallout being dm_merge_bvec() would only allow a single page to be added to a bio. This interim fix is minimal for the benefit of stable@ because the more comprehensive cleanup of passing a sector_t to all DM targets' merge function will impact quite a few DM targets. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Cc: stable@vger.kernel.org # 3.19+
1 files changed, 12 insertions, 5 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index e24069aaeb18..2caf492890d6 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1723,8 +1723,7 @@ static int dm_merge_bvec(struct request_queue *q,
struct mapped_device *md = q->queuedata;
struct dm_table *map = dm_get_live_table_fast(md);
struct dm_target *ti;
- sector_t max_sectors;
- int max_size = 0;
+ sector_t max_sectors, max_size = 0;
if (unlikely(!map))
goto out;
@@ -1739,8 +1738,16 @@ static int dm_merge_bvec(struct request_queue *q,
max_sectors = min(max_io_len(bvm->bi_sector, ti),
(sector_t) queue_max_sectors(q));
max_size = (max_sectors << SECTOR_SHIFT) - bvm->bi_size;
- if (unlikely(max_size < 0)) /* this shouldn't _ever_ happen */
- max_size = 0;
+ /*
+ * FIXME: this stop-gap fix _must_ be cleaned up (by passing a sector_t
+ * to the targets' merge function since it holds sectors not bytes).
+ * Just doing this as an interim fix for stable@ because the more
+ * comprehensive cleanup of switching to sector_t will impact every
+ * DM target that implements a ->merge hook.
+ */
+ if (max_size > INT_MAX)
+ max_size = INT_MAX;
* merge_bvec_fn() returns number of bytes
@@ -1748,7 +1755,7 @@ static int dm_merge_bvec(struct request_queue *q,
* max is precomputed maximal io size
if (max_size && ti->type->merge)
- max_size = ti->type->merge(ti, bvm, biovec, max_size);
+ max_size = ti->type->merge(ti, bvm, biovec, (int) max_size);
* If the target doesn't support merge method and some of the devices
* provided their merge_bvec method (we know this by looking for the