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dm space map: disallow decrementing a reference count below zero

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The old behaviour, returning -EINVAL if a ref_count of 0 would be
decremented, was removed in commit f722063 ("dm space map: optimise
sm_ll_dec and sm_ll_inc").  To fix this regression we return an error
code from the mutator function pointer passed to sm_ll_mutate() and have
dec_ref_count() return -EINVAL if the old ref_count is 0.

Add a DMERR to reflect the potential seriousness of this error.

Also, add missing dm_tm_unlock() to sm_ll_mutate()'s error path.

With this fix the following dmts regression test now passes:
 dmtest run --suite cache -n /metadata_use_kernel/

The next patch fixes the higher-level dm-array code that exposed this
regression.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 3.12+
This commit is contained in:
Joe Thornber 2013-12-13 12:31:08 +00:00 committed by Mike Snitzer
parent 76f5bee5c3
commit 5b564d80f8
1 changed files with 23 additions and 9 deletions
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32
drivers/md/persistent-data/dm-space-map-common.c
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@ -381,7 +381,7 @@ int sm_ll_find_free_block(struct ll_disk *ll, dm_block_t begin,
}
static int sm_ll_mutate(struct ll_disk *ll, dm_block_t b,
uint32_t (*mutator)(void *context, uint32_t old),
int (*mutator)(void *context, uint32_t old, uint32_t *new),
void *context, enum allocation_event *ev)
{
int r;
@ -410,11 +410,17 @@ static int sm_ll_mutate(struct ll_disk *ll, dm_block_t b,
if (old > 2) {
r = sm_ll_lookup_big_ref_count(ll, b, &old);
if (r < 0)
if (r < 0) {
dm_tm_unlock(ll->tm, nb);
return r;
}
}
ref_count = mutator(context, old);
r = mutator(context, old, &ref_count);
if (r) {
dm_tm_unlock(ll->tm, nb);
return r;
}
if (ref_count <= 2) {
sm_set_bitmap(bm_le, bit, ref_count);
@ -465,9 +471,10 @@ static int sm_ll_mutate(struct ll_disk *ll, dm_block_t b,
return ll->save_ie(ll, index, &ie_disk);
}
static uint32_t set_ref_count(void *context, uint32_t old)
static int set_ref_count(void *context, uint32_t old, uint32_t *new)
{
return *((uint32_t *) context);
*new = *((uint32_t *) context);
return 0;
}
int sm_ll_insert(struct ll_disk *ll, dm_block_t b,
@ -476,9 +483,10 @@ int sm_ll_insert(struct ll_disk *ll, dm_block_t b,
return sm_ll_mutate(ll, b, set_ref_count, &ref_count, ev);
}
static uint32_t inc_ref_count(void *context, uint32_t old)
static int inc_ref_count(void *context, uint32_t old, uint32_t *new)
{
return old + 1;
*new = old + 1;
return 0;
}
int sm_ll_inc(struct ll_disk *ll, dm_block_t b, enum allocation_event *ev)
@ -486,9 +494,15 @@ int sm_ll_inc(struct ll_disk *ll, dm_block_t b, enum allocation_event *ev)
return sm_ll_mutate(ll, b, inc_ref_count, NULL, ev);
}
static uint32_t dec_ref_count(void *context, uint32_t old)
static int dec_ref_count(void *context, uint32_t old, uint32_t *new)
{
return old - 1;
if (!old) {
DMERR_LIMIT("unable to decrement a reference count below 0");
return -EINVAL;
}
*new = old - 1;
return 0;
}
int sm_ll_dec(struct ll_disk *ll, dm_block_t b, enum allocation_event *ev)