@@ -163,7 +163,7 @@ struct cache {
/*
* origin_blocks entries, discarded if set.
*/
- uint32_t discard_block_size; /* a power of 2 times sectors per block */
+ uint32_t discard_block_size;
dm_dblock_t discard_nr_blocks;
unsigned long *discard_bitset;
@@ -1905,35 +1905,6 @@ static int create_cache_policy(struct cache *cache, struct cache_args *ca,
return 0;
}
-/*
- * We want the discard block size to be a power of two, at least the size
- * of the cache block size, and have no more than 2^14 discard blocks
- * across the origin.
- */
-#define MAX_DISCARD_BLOCKS (1 << 14)
-
-static bool too_many_discard_blocks(sector_t discard_block_size,
- sector_t origin_size)
-{
- (void) sector_div(origin_size, discard_block_size);
-
- return origin_size > MAX_DISCARD_BLOCKS;
-}
-
-static sector_t calculate_discard_block_size(sector_t cache_block_size,
- sector_t origin_size)
-{
- sector_t discard_block_size;
-
- discard_block_size = roundup_pow_of_two(cache_block_size);
-
- if (origin_size)
- while (too_many_discard_blocks(discard_block_size, origin_size))
- discard_block_size *= 2;
-
- return discard_block_size;
-}
-
#define DEFAULT_MIGRATION_THRESHOLD 2048
static int cache_create(struct cache_args *ca, struct cache **result)
@@ -2038,9 +2009,7 @@ static int cache_create(struct cache_args *ca, struct cache **result)
}
clear_bitset(cache->dirty_bitset, from_cblock(cache->cache_size));
- cache->discard_block_size =
- calculate_discard_block_size(cache->sectors_per_block,
- cache->origin_sectors);
+ cache->discard_block_size = cache->sectors_per_block;
cache->discard_nr_blocks = oblock_to_dblock(cache, cache->origin_blocks);
cache->discard_bitset = alloc_bitset(from_dblock(cache->discard_nr_blocks));
if (!cache->discard_bitset) {
@@ -2627,7 +2596,7 @@ static void set_discard_limits(struct cache *cache, struct queue_limits *limits)
/*
* FIXME: these limits may be incompatible with the cache device
*/
- limits->max_discard_sectors = cache->discard_block_size * 1024;
+ limits->max_discard_sectors = cache->discard_block_size;
limits->discard_granularity = cache->discard_block_size << SECTOR_SHIFT;
}
This is a note to let you know that I have just added a patch titled dm cache: prevent corruption caused by discard_block_size > cache_block_size to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.11.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From 1d862ed9142e4e4d4b2aa3fd773f17082c891ec0 Mon Sep 17 00:00:00 2001 From: Mike Snitzer <snitzer@redhat.com> Date: Thu, 20 Mar 2014 10:11:15 -0400 Subject: dm cache: prevent corruption caused by discard_block_size > cache_block_size commit d132cc6d9e92424bb9d4fd35f5bd0e55d583f4be upstream. If the discard block size is larger than the cache block size we will not properly quiesce IO to a region that is about to be discarded. This results in a race between a cache migration where no copy is needed, and a write to an adjacent cache block that's within the same large discard block. Workaround this by limiting the discard_block_size to cache_block_size. Also limit the max_discard_sectors to cache_block_size. A more comprehensive fix that introduces range locking support in the bio_prison and proper quiescing of a discard range that spans multiple cache blocks is already in development. Reported-by: Morgan Mears <Morgan.Mears@netapp.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Acked-by: Joe Thornber <ejt@redhat.com> Acked-by: Heinz Mauelshagen <heinzm@redhat.com> [ luis: backported to 3.11: adjusted context ] Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- drivers/md/dm-cache-target.c | 37 +++---------------------------------- 1 file changed, 3 insertions(+), 34 deletions(-) -- 1.9.1