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authorMike Snitzer <snitzer@redhat.com>2015-08-03 09:54:58 -0400
committerMike Snitzer <snitzer@redhat.com>2015-08-03 22:49:59 -0400
commitbd4aaf8f9b85d6b2df3231fd62b219ebb75d3568 (patch)
tree00b52bacf20f8c239e0edbbac3b8047f98c0bb0e
parent795e633a2dc6cbbeac68bc7f6006082150d38bb7 (diff)
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+
-rw-r--r--drivers/md/dm.c27
1 files changed, 10 insertions, 17 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index ab37ae114e94..0d7ab20c58df 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1729,7 +1729,8 @@ static int dm_merge_bvec(struct request_queue *q,
1729 struct mapped_device *md = q->queuedata; 1729 struct mapped_device *md = q->queuedata;
1730 struct dm_table *map = dm_get_live_table_fast(md); 1730 struct dm_table *map = dm_get_live_table_fast(md);
1731 struct dm_target *ti; 1731 struct dm_target *ti;
1732 sector_t max_sectors, max_size = 0; 1732 sector_t max_sectors;
1733 int max_size = 0;
1733 1734
1734 if (unlikely(!map)) 1735 if (unlikely(!map))
1735 goto out; 1736 goto out;
@@ -1742,18 +1743,10 @@ static int dm_merge_bvec(struct request_queue *q,
1742 * Find maximum amount of I/O that won't need splitting 1743 * Find maximum amount of I/O that won't need splitting
1743 */ 1744 */
1744 max_sectors = min(max_io_len(bvm->bi_sector, ti), 1745 max_sectors = min(max_io_len(bvm->bi_sector, ti),
1745 (sector_t) queue_max_sectors(q)); 1746 (sector_t) BIO_MAX_SECTORS);
1746 max_size = (max_sectors << SECTOR_SHIFT) - bvm->bi_size; 1747 max_size = (max_sectors << SECTOR_SHIFT) - bvm->bi_size;
1747 1748 if (max_size < 0)
1748 /* 1749 max_size = 0;
1749 * FIXME: this stop-gap fix _must_ be cleaned up (by passing a sector_t
1750 * to the targets' merge function since it holds sectors not bytes).
1751 * Just doing this as an interim fix for stable@ because the more
1752 * comprehensive cleanup of switching to sector_t will impact every
1753 * DM target that implements a ->merge hook.
1754 */
1755 if (max_size > INT_MAX)
1756 max_size = INT_MAX;
1757 1750
1758 /* 1751 /*
1759 * merge_bvec_fn() returns number of bytes 1752 * merge_bvec_fn() returns number of bytes
@@ -1761,13 +1754,13 @@ static int dm_merge_bvec(struct request_queue *q,
1761 * max is precomputed maximal io size 1754 * max is precomputed maximal io size
1762 */ 1755 */
1763 if (max_size && ti->type->merge) 1756 if (max_size && ti->type->merge)
1764 max_size = ti->type->merge(ti, bvm, biovec, (int) max_size); 1757 max_size = ti->type->merge(ti, bvm, biovec, max_size);
1765 /* 1758 /*
1766 * If the target doesn't support merge method and some of the devices 1759 * If the target doesn't support merge method and some of the devices
1767 * provided their merge_bvec method (we know this by looking for the 1760 * provided their merge_bvec method (we know this by looking at
1768 * max_hw_sectors that dm_set_device_limits may set), then we can't 1761 * queue_max_hw_sectors), then we can't allow bios with multiple vector
1769 * allow bios with multiple vector entries. So always set max_size 1762 * entries. So always set max_size to 0, and the code below allows
1770 * to 0, and the code below allows just one page. 1763 * just one page.
1771 */ 1764 */
1772 else if (queue_max_hw_sectors(q) <= PAGE_SIZE >> 9) 1765 else if (queue_max_hw_sectors(q) <= PAGE_SIZE >> 9)
1773 max_size = 0; 1766 max_size = 0;