dm thin metadata: Add support for a pre-commit callback

commit ecda7c0280e6b3398459dc589b9a41c1adb45529 upstream.

Add support for one pre-commit callback which is run right before the
metadata are committed.

This allows the thin provisioning target to run a callback before the
metadata are committed and is required by the next commit.

Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com>
Acked-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
[bwh: Backported to 3.16:
 - Open-code pmd_write_{lock_in_core,unlock}()
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c
index e6f64c472d5e47ae9edf12a5f088ceaae8a0793a..da54c8172df0b4ec5f3d1289af907415bd67b025 100644 (file)
--- a/drivers/md/dm-thin-metadata.c
+++ b/drivers/md/dm-thin-metadata.c
@@ -197,6 +197,15 @@ struct dm_pool_metadata {
         */
        bool fail_io:1;
 
+       /*
+        * Pre-commit callback.
+        *
+        * This allows the thin provisioning target to run a callback before
+        * the metadata are committed.
+        */
+       dm_pool_pre_commit_fn pre_commit_fn;
+       void *pre_commit_context;
+
        /*
         * Reading the space map roots can fail, so we read it into these
         * buffers before the superblock is locked and updated.
@@ -784,6 +793,14 @@ static int __commit_transaction(struct dm_pool_metadata *pmd)
         */
        BUILD_BUG_ON(sizeof(struct thin_disk_superblock) > 512);
 
+       if (pmd->pre_commit_fn) {
+               r = pmd->pre_commit_fn(pmd->pre_commit_context);
+               if (r < 0) {
+                       DMERR("pre-commit callback failed");
+                       return r;
+               }
+       }
+
        r = __write_changed_details(pmd);
        if (r < 0)
                return r;
@@ -844,6 +861,8 @@ struct dm_pool_metadata *dm_pool_metadata_open(struct block_device *bdev,
        pmd->fail_io = false;
        pmd->bdev = bdev;
        pmd->data_block_size = data_block_size;
+       pmd->pre_commit_fn = NULL;
+       pmd->pre_commit_context = NULL;
 
        r = __create_persistent_data_objects(pmd, format_device);
        if (r) {
@@ -1789,6 +1808,16 @@ int dm_pool_register_metadata_threshold(struct dm_pool_metadata *pmd,
        return r;
 }
 
+void dm_pool_register_pre_commit_callback(struct dm_pool_metadata *pmd,
+                                         dm_pool_pre_commit_fn fn,
+                                         void *context)
+{
+       down_write(&pmd->root_lock);
+       pmd->pre_commit_fn = fn;
+       pmd->pre_commit_context = context;
+       up_write(&pmd->root_lock);
+}
+
 int dm_pool_metadata_set_needs_check(struct dm_pool_metadata *pmd)
 {
        int r;

diff --git a/drivers/md/dm-thin-metadata.h b/drivers/md/dm-thin-metadata.h
index e3c857db195a7453d192f5f55cfb766a046a789a..9859dd9fb921ef413a21fd110e35531d25ef4643 100644 (file)
--- a/drivers/md/dm-thin-metadata.h
+++ b/drivers/md/dm-thin-metadata.h
@@ -213,6 +213,13 @@ int dm_pool_register_metadata_threshold(struct dm_pool_metadata *pmd,
 int dm_pool_metadata_set_needs_check(struct dm_pool_metadata *pmd);
 bool dm_pool_metadata_needs_check(struct dm_pool_metadata *pmd);
 
+/* Pre-commit callback */
+typedef int (*dm_pool_pre_commit_fn)(void *context);
+
+void dm_pool_register_pre_commit_callback(struct dm_pool_metadata *pmd,
+                                         dm_pool_pre_commit_fn fn,
+                                         void *context);
+
 /*----------------------------------------------------------------*/
 
 #endif