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>

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 1c9157e..817fc19 100644 (file)
--- 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 703238e..9d8e2b8 100644 (file)
--- 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);