Commit 1c220c69 authored by Joe Thornber's avatar Joe Thornber Committed by Mike Snitzer

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: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 3.19+
parent 15b94a69
...@@ -1723,8 +1723,7 @@ static int dm_merge_bvec(struct request_queue *q, ...@@ -1723,8 +1723,7 @@ static int dm_merge_bvec(struct request_queue *q,
struct mapped_device *md = q->queuedata; struct mapped_device *md = q->queuedata;
struct dm_table *map = dm_get_live_table_fast(md); struct dm_table *map = dm_get_live_table_fast(md);
struct dm_target *ti; struct dm_target *ti;
sector_t max_sectors; sector_t max_sectors, max_size = 0;
int max_size = 0;
if (unlikely(!map)) if (unlikely(!map))
goto out; goto out;
...@@ -1739,8 +1738,16 @@ static int dm_merge_bvec(struct request_queue *q, ...@@ -1739,8 +1738,16 @@ static int dm_merge_bvec(struct request_queue *q,
max_sectors = min(max_io_len(bvm->bi_sector, ti), max_sectors = min(max_io_len(bvm->bi_sector, ti),
(sector_t) queue_max_sectors(q)); (sector_t) queue_max_sectors(q));
max_size = (max_sectors << SECTOR_SHIFT) - bvm->bi_size; 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 * merge_bvec_fn() returns number of bytes
...@@ -1748,7 +1755,7 @@ static int dm_merge_bvec(struct request_queue *q, ...@@ -1748,7 +1755,7 @@ static int dm_merge_bvec(struct request_queue *q,
* max is precomputed maximal io size * max is precomputed maximal io size
*/ */
if (max_size && ti->type->merge) 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 * 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 * provided their merge_bvec method (we know this by looking for the
......
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