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dm: fix dm_merge_bvec regression on 32 bit systems 

A DM regression on 32 bit systems was reported against v4.2-rc3 here:
https://lkml.org/lkml/2015/7/29/401

Fix this by reverting both commit 1c220c69 ("dm: fix casting bug in
dm_merge_bvec()") and 148e51ba ("dm: improve documentation and code
clarity in dm_merge_bvec").  This combined revert is done to eliminate
the possibility of a partial revert in stable@ kernels.

In hindsight the correct fix, at the time 1c220c69 was applied to fix
the regression that 148e51ba introduced, should've been to simply revert
148e51ba.

Reported-by: Josh Boyer <jwboyer@fedoraproject.org>
Tested-by: Adam Williamson <awilliam@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 3.19+
This commit is contained in:
Mike Snitzer 2015-08-03 09:54:58 -04:00
parent 795e633a2d
commit bd4aaf8f9b
1 changed files with 10 additions and 17 deletions
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27
drivers/md/dm.c
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@ -1729,7 +1729,8 @@ 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, max_size = 0;
sector_t max_sectors;
int max_size = 0;
if (unlikely(!map))
goto out;
@ -1742,18 +1743,10 @@ static int dm_merge_bvec(struct request_queue *q,
* Find maximum amount of I/O that won't need splitting
*/
max_sectors = min(max_io_len(bvm->bi_sector, ti),
(sector_t) queue_max_sectors(q));
(sector_t) BIO_MAX_SECTORS);
max_size = (max_sectors << SECTOR_SHIFT) - bvm->bi_size;
/*
* 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;
if (max_size < 0)
max_size = 0;
/*
* merge_bvec_fn() returns number of bytes
@ -1761,13 +1754,13 @@ 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, (int) max_size);
max_size = ti->type->merge(ti, bvm, biovec, 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
* max_hw_sectors that dm_set_device_limits may set), then we can't
* allow bios with multiple vector entries. So always set max_size
* to 0, and the code below allows just one page.
* provided their merge_bvec method (we know this by looking at
* queue_max_hw_sectors), then we can't allow bios with multiple vector
* entries. So always set max_size to 0, and the code below allows
* just one page.
*/
else if (queue_max_hw_sectors(q) <= PAGE_SIZE >> 9)
max_size = 0;