@@ -157,7 +157,7 @@ struct cache {
/*
* cache_size entries, dirty if set
*/
- dm_cblock_t nr_dirty;
+ atomic_t nr_dirty;
unsigned long *dirty_bitset;
/*
@@ -406,7 +406,7 @@ static bool is_dirty(struct cache *cache, dm_cblock_t b)
static void set_dirty(struct cache *cache, dm_oblock_t oblock, dm_cblock_t cblock)
{
if (!test_and_set_bit(from_cblock(cblock), cache->dirty_bitset)) {
- cache->nr_dirty = to_cblock(from_cblock(cache->nr_dirty) + 1);
+ atomic_inc(&cache->nr_dirty);
policy_set_dirty(cache->policy, oblock);
}
}
@@ -415,8 +415,7 @@ static void clear_dirty(struct cache *cache, dm_oblock_t oblock, dm_cblock_t cbl
{
if (test_and_clear_bit(from_cblock(cblock), cache->dirty_bitset)) {
policy_clear_dirty(cache->policy, oblock);
- cache->nr_dirty = to_cblock(from_cblock(cache->nr_dirty) - 1);
- if (!from_cblock(cache->nr_dirty))
+ if (atomic_dec_return(&cache->nr_dirty) == 0)
dm_table_event(cache->ti->table);
}
}
@@ -2003,7 +2002,7 @@ static int cache_create(struct cache_args *ca, struct cache **result)
atomic_set(&cache->quiescing_ack, 0);
r = -ENOMEM;
- cache->nr_dirty = 0;
+ atomic_set(&cache->nr_dirty, 0);
cache->dirty_bitset = alloc_bitset(from_cblock(cache->cache_size));
if (!cache->dirty_bitset) {
*error = "could not allocate dirty bitset";
@@ -2475,7 +2474,7 @@ static void cache_status(struct dm_target *ti, status_type_t type,
residency = policy_residency(cache->policy);
- DMEMIT("%llu/%llu %u %u %u %u %u %u %llu %u ",
+ DMEMIT("%llu/%llu %u %u %u %u %u %u %llu %lu ",
(unsigned long long)(nr_blocks_metadata - nr_free_blocks_metadata),
(unsigned long long)nr_blocks_metadata,
(unsigned) atomic_read(&cache->stats.read_hit),
@@ -2485,7 +2484,7 @@ static void cache_status(struct dm_target *ti, status_type_t type,
(unsigned) atomic_read(&cache->stats.demotion),
(unsigned) atomic_read(&cache->stats.promotion),
(unsigned long long) from_cblock(residency),
- cache->nr_dirty);
+ (unsigned long) atomic_read(&cache->nr_dirty));
if (cache->features.write_through)
DMEMIT("1 writethrough ");
This is a note to let you know that I have just added a patch titled dm cache: fix race affecting dirty block count 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 e7061fafa053557a37ed202a32f7272e147296b2 Mon Sep 17 00:00:00 2001 From: Anssi Hannula <anssi.hannula@iki.fi> Date: Fri, 1 Aug 2014 11:55:47 -0400 Subject: dm cache: fix race affecting dirty block count commit 44fa816bb778edbab6b6ddaaf24908dd6295937e upstream. nr_dirty is updated without locking, causing it to drift so that it is non-zero (either a small positive integer, or a very large one when an underflow occurs) even when there are no actual dirty blocks. This was due to a race between the workqueue and map function accessing nr_dirty in parallel without proper protection. People were seeing under runs due to a race on increment/decrement of nr_dirty, see: https://lkml.org/lkml/2014/6/3/648 Fix this by using an atomic_t for nr_dirty. Reported-by: roma1390@gmail.com Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi> Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> [ luis: backported to 3.11: adjusted context ] Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- drivers/md/dm-cache-target.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) -- 1.9.1