dm thin metadata: introduce dm_pool_metadata_set_read_only

Introduce dm_pool_metadata_set_read_only to put the underlying block
manager into read-only mode.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c
index 4f5b11c..d30bc09 100644 (file)
--- a/drivers/md/dm-thin-metadata.c
+++ b/drivers/md/dm-thin-metadata.c
@@ -184,6 +184,7 @@ struct dm_pool_metadata {
        uint64_t trans_id;
        unsigned long flags;
        sector_t data_block_size;
+       bool read_only:1;
 };
 
 struct dm_thin_device {
@@ -807,6 +808,7 @@ struct dm_pool_metadata *dm_pool_metadata_open(struct block_device *bdev,
        init_rwsem(&pmd->root_lock);
        pmd->time = 0;
        INIT_LIST_HEAD(&pmd->thin_devices);
+       pmd->read_only = false;
        pmd->bdev = bdev;
        pmd->data_block_size = data_block_size;
 
@@ -849,10 +851,12 @@ int dm_pool_metadata_close(struct dm_pool_metadata *pmd)
                return -EBUSY;
        }
 
-       r = __commit_transaction(pmd);
-       if (r < 0)
-               DMWARN("%s: __commit_transaction() failed, error = %d",
-                      __func__, r);
+       if (!pmd->read_only) {
+               r = __commit_transaction(pmd);
+               if (r < 0)
+                       DMWARN("%s: __commit_transaction() failed, error = %d",
+                              __func__, r);
+       }
 
        __destroy_persistent_data_objects(pmd);
        kfree(pmd);
@@ -1587,3 +1591,11 @@ int dm_pool_resize_data_dev(struct dm_pool_metadata *pmd, dm_block_t new_count)
 
        return r;
 }
+
+void dm_pool_metadata_read_only(struct dm_pool_metadata *pmd)
+{
+       down_write(&pmd->root_lock);
+       pmd->read_only = true;
+       dm_bm_set_read_only(pmd->bm);
+       up_write(&pmd->root_lock);
+}

diff --git a/drivers/md/dm-thin-metadata.h b/drivers/md/dm-thin-metadata.h
index 1632fec..2bbe622 100644 (file)
--- a/drivers/md/dm-thin-metadata.h
+++ b/drivers/md/dm-thin-metadata.h
@@ -174,6 +174,12 @@ int dm_pool_get_data_dev_size(struct dm_pool_metadata *pmd, dm_block_t *result);
  */
 int dm_pool_resize_data_dev(struct dm_pool_metadata *pmd, dm_block_t new_size);
 
+/*
+ * Flicks the underlying block manager into read only mode, so you know
+ * that nothing is changing.
+ */
+void dm_pool_metadata_read_only(struct dm_pool_metadata *pmd);
+
 /*----------------------------------------------------------------*/
 
 #endif