linux-kernel - [PATCH 4.4 32/91] dm cache: fix corruption seen when using cache

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Date:   Fri, 10 Mar 2017 10:08:31 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Joe Thornber <ejt@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>
Subject: [PATCH 4.4 32/91] dm cache: fix corruption seen when using cache > 2TB

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Joe Thornber <ejt@...hat.com>

commit ca763d0a53b264a650342cee206512bc92ac7050 upstream.

A rounding bug due to compiler generated temporary being 32bit was found
in remap_to_cache().  A localized cast in remap_to_cache() fixes the
corruption but this preferred fix (changing from uint32_t to sector_t)
eliminates potential for future rounding errors elsewhere.

Signed-off-by: Joe Thornber <ejt@...hat.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/md/dm-cache-target.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -251,7 +251,7 @@ struct cache {
 	/*
 	 * Fields for converting from sectors to blocks.
 	 */
-	uint32_t sectors_per_block;
+	sector_t sectors_per_block;
 	int sectors_per_block_shift;
 
 	spinlock_t lock;
@@ -3547,11 +3547,11 @@ static void cache_status(struct dm_targe
 
 		residency = policy_residency(cache->policy);
 
-		DMEMIT("%u %llu/%llu %u %llu/%llu %u %u %u %u %u %u %lu ",
+		DMEMIT("%u %llu/%llu %llu %llu/%llu %u %u %u %u %u %u %lu ",
 		       (unsigned)DM_CACHE_METADATA_BLOCK_SIZE,
 		       (unsigned long long)(nr_blocks_metadata - nr_free_blocks_metadata),
 		       (unsigned long long)nr_blocks_metadata,
-		       cache->sectors_per_block,
+		       (unsigned long long)cache->sectors_per_block,
 		       (unsigned long long) from_cblock(residency),
 		       (unsigned long long) from_cblock(cache->cache_size),
 		       (unsigned) atomic_read(&cache->stats.read_hit),