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Commit 94563bad authored by Mike Snitzer's avatar Mike Snitzer
Browse files

dm thin: always return -ENOSPC if no_free_space is set 



If pool has 'no_free_space' set it means a previous allocation already
determined the pool has no free space (and failed that allocation with
-ENOSPC).  By always returning -ENOSPC if 'no_free_space' is set, we do
not allow the pool to oscillate between allocating blocks and then not.

But a side-effect of this determinism is that if a user wants to be able
to allocate new blocks they'll need to reload the pool's table (to clear
the 'no_free_space' flag).  This reload will happen automatically if the
pool's data volume is resized.  But if the user takes action to free a
lot of space by deleting snapshot volumes, etc the pool will no longer
allow data allocations to continue without an intervening table reload.

Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Acked-by: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent f11c1c56

drivers/md/dm-thin.c

+31 −25
Original line number Diff line number Diff line
@@ -918,6 +918,13 @@ static int alloc_data_block(struct thin_c *tc, dm_block_t *result) 
	unsigned long flags;

	struct pool *pool = tc->pool;



	/*

	 * Once no_free_space is set we must not allow allocation to succeed.

	 * Otherwise it is difficult to explain, debug, test and support.

	 */

	if (pool->no_free_space)

		return -ENOSPC;



	r = dm_pool_get_free_block_count(pool->pmd, &free_blocks);

	if (r)

		return r;
@@ -932,9 +939,6 @@ static int alloc_data_block(struct thin_c *tc, dm_block_t *result) 
	}



	if (!free_blocks) {

		if (pool->no_free_space)

			return -ENOSPC;

		else {

		/*

		 * Try to commit to see if that will free up some

		 * more space.
@@ -947,7 +951,10 @@ static int alloc_data_block(struct thin_c *tc, dm_block_t *result) 


		/*

		 * If we still have no space we set a flag to avoid

			 * doing all this checking and return -ENOSPC.

		 * doing all this checking and return -ENOSPC.  This

		 * flag serves as a latch that disallows allocations from

		 * this pool until the admin takes action (e.g. resize or

		 * table reload).

		 */

		if (!free_blocks) {

			DMWARN("%s: no free space available.",
@@ -958,7 +965,6 @@ static int alloc_data_block(struct thin_c *tc, dm_block_t *result) 
			return -ENOSPC;

		}

	}

	}



	r = dm_pool_alloc_data_block(pool->pmd, result);

	if (r)
@@ -2695,7 +2701,7 @@ static struct target_type pool_target = { 
	.name = "thin-pool",

	.features = DM_TARGET_SINGLETON | DM_TARGET_ALWAYS_WRITEABLE |

		    DM_TARGET_IMMUTABLE,

	.version = {1, 8, 0},

	.version = {1, 9, 0},

	.module = THIS_MODULE,

	.ctr = pool_ctr,

	.dtr = pool_dtr,
@@ -2982,7 +2988,7 @@ static int thin_iterate_devices(struct dm_target *ti, 


static struct target_type thin_target = {

	.name = "thin",

	.version = {1, 8, 0},

	.version = {1, 9, 0},

	.module	= THIS_MODULE,

	.ctr = thin_ctr,

	.dtr = thin_dtr,