[PATCH 3.16 065/245] dm thin metadata: Add support for a pre-commit callback

Ben Hutchings
2020-04-23T23:21:29Z

From: Nikos Tsironis <ntsironis@arrikto.com>

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>
---
drivers/md/dm-thin-metadata.c | 29 +++++++++++++++++++++++++++++
drivers/md/dm-thin-metadata.h | 7 +++++++
2 files changed, 36 insertions(+)

--- a/drivers/md/dm-thin-metadata.c
+++ b/drivers/md/dm-thin-metadata.c
@@ -198,6 +198,15 @@ 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 d
*/
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_metadat
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(
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;
--- a/drivers/md/dm-thin-metadata.h
+++ b/drivers/md/dm-thin-metadata.h
@@ -213,6 +213,13 @@ int dm_pool_register_metadata_threshold(
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