dm thin: fix missing out-of-data-space to write mode transition if blocks are released

Discard bios and thin device deletion have the potential to release data
blocks.  If the thin-pool is in out-of-data-space mode, and blocks were
released, transition the thin-pool back to full write mode.

The correct time to do this is just after the thin-pool metadata commit.
It cannot be done before the commit because the space maps will not
allow immediate reuse of the data blocks in case there's a rollback
following power failure.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org

1 files changed, 20 insertions, 2 deletions

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 14b51a4fdf6b..922aa553e9e0 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -1127,6 +1127,24 @@ static void schedule_external_copy(struct thin_c *tc, dm_block_t virt_block,
                 schedule_zero(tc, virt_block, data_dest, cell, bio);
 }
 
+static void set_pool_mode(struct pool *pool, enum pool_mode new_mode);
+
+static void check_for_space(struct pool *pool)
+{
+        int r;
+        dm_block_t nr_free;
+
+        if (get_pool_mode(pool) != PM_OUT_OF_DATA_SPACE)
+                return;
+
+        r = dm_pool_get_free_block_count(pool->pmd, &nr_free);
+        if (r)
+                return;
+
+        if (nr_free)
+                set_pool_mode(pool, PM_WRITE);
+}
+
 /*
  * A non-zero return indicates read_only or fail_io mode.
  * Many callers don't care about the return value.
@@ -1141,6 +1159,8 @@ static int commit(struct pool *pool)
         r = dm_pool_commit_metadata(pool->pmd);
         if (r)
                 metadata_operation_failed(pool, "dm_pool_commit_metadata", r);
+        else
+                check_for_space(pool);
 
         return r;
 }
@@ -1159,8 +1179,6 @@ static void check_low_water_mark(struct pool *pool, dm_block_t free_blocks)
         }
 }
 
-static void set_pool_mode(struct pool *pool, enum pool_mode new_mode);
-
 static int alloc_data_block(struct thin_c *tc, dm_block_t *result)
 {
         int r;