btrfs: Add sysfs support for metadata_uuid feature

Since the metadata_uuid is a new incompat feature it requires the
respective sysfs hooks. This patch adds the 'metdata_uuid' feature to
be shown if it supported by the kernel. Additionally it adds
/sys/fs/btrfs/UUID/metadata_uuid attribute which allows one to read
the current metadata_uuid.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 3717c864ba2316ccc9e9ef319c7a0008afa59039..5a5930e3d32b1346b15258cf0e7ed5b4158406fc 100644 (file)
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -191,6 +191,7 @@ BTRFS_FEAT_ATTR_INCOMPAT(extended_iref, EXTENDED_IREF);
 BTRFS_FEAT_ATTR_INCOMPAT(raid56, RAID56);
 BTRFS_FEAT_ATTR_INCOMPAT(skinny_metadata, SKINNY_METADATA);
 BTRFS_FEAT_ATTR_INCOMPAT(no_holes, NO_HOLES);
+BTRFS_FEAT_ATTR_INCOMPAT(metadata_uuid, METADATA_UUID);
 BTRFS_FEAT_ATTR_COMPAT_RO(free_space_tree, FREE_SPACE_TREE);
 
 static struct attribute *btrfs_supported_feature_attrs[] = {
@@ -204,6 +205,7 @@ static struct attribute *btrfs_supported_feature_attrs[] = {
        BTRFS_FEAT_ATTR_PTR(raid56),
        BTRFS_FEAT_ATTR_PTR(skinny_metadata),
        BTRFS_FEAT_ATTR_PTR(no_holes),
+       BTRFS_FEAT_ATTR_PTR(metadata_uuid),
        BTRFS_FEAT_ATTR_PTR(free_space_tree),
        NULL
 };
@@ -505,12 +507,24 @@ static ssize_t quota_override_store(struct kobject *kobj,
 
 BTRFS_ATTR_RW(, quota_override, quota_override_show, quota_override_store);
 
+static ssize_t btrfs_metadata_uuid_show(struct kobject *kobj,
+                               struct kobj_attribute *a, char *buf)
+{
+       struct btrfs_fs_info *fs_info = to_fs_info(kobj);
+
+       return snprintf(buf, PAGE_SIZE, "%pU\n",
+                       fs_info->fs_devices->metadata_uuid);
+}
+
+BTRFS_ATTR(, metadata_uuid, btrfs_metadata_uuid_show);
+
 static const struct attribute *btrfs_attrs[] = {
        BTRFS_ATTR_PTR(, label),
        BTRFS_ATTR_PTR(, nodesize),
        BTRFS_ATTR_PTR(, sectorsize),
        BTRFS_ATTR_PTR(, clone_alignment),
        BTRFS_ATTR_PTR(, quota_override),
+       BTRFS_ATTR_PTR(, metadata_uuid),
        NULL,
 };