btrfs: introduce pending action: commit

In some contexts, like in sysfs handlers, we don't want to trigger a
transaction commit. It's a heavy operation, we don't know what external
locks may be taken. Instead, make it possible to finish the operation
through sync syscall or SYNC_FS ioctl.

Signed-off-by: David Sterba <dsterba@suse.cz>

2 files changed, 6 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 1c9157e4ab0c..817fc19b8159 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2132,6 +2132,7 @@ struct btrfs_ioctl_defrag_range_args {
 
 #define BTRFS_PENDING_SET_INODE_MAP_CACHE       (0)
 #define BTRFS_PENDING_CLEAR_INODE_MAP_CACHE     (1)
+#define BTRFS_PENDING_COMMIT                    (2)
 
 #define btrfs_test_pending(info, opt)   \
         test_bit(BTRFS_PENDING_##opt, &(info)->pending_changes)
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 703238ed7337..9d8e2b8d12b4 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -2036,6 +2036,11 @@ void btrfs_apply_pending_changes(struct btrfs_fs_info *fs_info)
                 btrfs_clear_opt(fs_info->mount_opt, INODE_MAP_CACHE);
         prev &= ~bit;
 
+        bit = 1 << BTRFS_PENDING_COMMIT;
+        if (prev & bit)
+                btrfs_debug(fs_info, "pending commit done");
+        prev &= ~bit;
+
         if (prev)
                 btrfs_warn(fs_info,
                         "unknown pending changes left 0x%lx, ignoring", prev);