summaryrefslogtreecommitdiffstats
path: root/drivers/md
diff options
context:
space:
mode:
authorMike Snitzer <snitzer@redhat.com>2013-08-22 09:56:18 -0400
committerMike Snitzer <snitzer@redhat.com>2013-09-05 20:46:06 -0400
commit94563badaf41f9291ff0bad94a443a4319b9e312 (patch)
tree6c9bf7f6aba642dd4a08035fe93ec683c3fdf5bf /drivers/md
parentf11c1c5693fac339d412b0b59b54693ddcb776ff (diff)
downloadlinux-94563badaf41f9291ff0bad94a443a4319b9e312.tar.gz
linux-94563badaf41f9291ff0bad94a443a4319b9e312.tar.bz2
linux-94563badaf41f9291ff0bad94a443a4319b9e312.zip
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>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm-thin.c56
1 files changed, 31 insertions, 25 deletions
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 3aff1c27e5b4..ed063427d676 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -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;
@@ -932,31 +939,30 @@ 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.
- */
- (void) commit_or_fallback(pool);
+ /*
+ * 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;
+ 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;
- }
+ /*
+ * 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;
}
}
@@ -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,