From c9de2830476185f839e6cf3f9a0e5d258a534d5d Mon Sep 17 00:00:00 2001
From: Mike Snitzer <snitzer@redhat.com>
Date: Mon, 3 Aug 2015 09:54:58 -0400
Subject: [PATCH] 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>
Acked-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 3.19+
---
drivers/md/dm.c | 27 ++++++++++-----------------
1 file 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,
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;
--
2.4.3