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Commit 5b564d80 authored by Joe Thornber's avatar Joe Thornber Committed by Mike Snitzer
Browse files

dm space map: disallow decrementing a reference count below zero 



The old behaviour, returning -EINVAL if a ref_count of 0 would be
decremented, was removed in commit f722063e ("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: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 3.12+
parent 76f5bee5

drivers/md/persistent-data/dm-space-map-common.c

+23 −9
Original line number Diff line number Diff line
@@ -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)