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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>
This commit is contained in:
Mike Snitzer 2013-08-22 09:56:18 -04:00
parent f11c1c5693
commit 94563badaf
1 changed files with 32 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

58
drivers/md/dm-thin.c
View File

@ -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)
/*
* 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 @@ 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,