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: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 3aff1c2..ed06342 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -918,6 +918,13 @@
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;
@@ -932,31 +939,30 @@
}
if (!free_blocks) {
- if (pool->no_free_space)
+ /*
+ * Try to commit to see if that will free up some
+ * more space.
+ */
+ (void) commit_or_fallback(pool);
+
+ r = dm_pool_get_free_block_count(pool->pmd, &free_blocks);
+ if (r)
+ return r;
+
+ /*
+ * If we still have no space we set a flag to avoid
+ * 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.",
+ dm_device_name(pool->pool_md));
+ spin_lock_irqsave(&pool->lock, flags);
+ pool->no_free_space = 1;
+ spin_unlock_irqrestore(&pool->lock, flags);
return -ENOSPC;
- else {
- /*
- * Try to commit to see if that will free up some
- * more space.
- */
- (void) commit_or_fallback(pool);
-
- r = dm_pool_get_free_block_count(pool->pmd, &free_blocks);
- if (r)
- return r;
-
- /*
- * If we still have no space we set a flag to avoid
- * doing all this checking and return -ENOSPC.
- */
- if (!free_blocks) {
- DMWARN("%s: no free space available.",
- dm_device_name(pool->pool_md));
- spin_lock_irqsave(&pool->lock, flags);
- pool->no_free_space = 1;
- spin_unlock_irqrestore(&pool->lock, flags);
- return -ENOSPC;
- }
}
}
@@ -2695,7 +2701,7 @@
.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 struct target_type thin_target = {
.name = "thin",
- .version = {1, 8, 0},
+ .version = {1, 9, 0},
.module = THIS_MODULE,
.ctr = thin_ctr,
.dtr = thin_dtr,