Btrfs: add snapshot/subvolume destroy ioctl

This patch adds snapshot/subvolume destroy ioctl.  A subvolume that isn't being
used and doesn't contains links to other subvolumes can be destroyed.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 35 insertions, 6 deletions

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 3be16ccc7eea..48a504260635 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -3203,6 +3203,7 @@ static int check_extent_flags(u64 flags)
         return 0;
 }
 
+
 static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
 {
         struct rb_root blocks = RB_ROOT;
@@ -3220,6 +3221,9 @@ static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
         if (!path)
                 return -ENOMEM;
 
+        rc->extents_found = 0;
+        rc->extents_skipped = 0;
+
         rc->search_start = rc->block_group->key.objectid;
         clear_extent_bits(&rc->processed_blocks, 0, (u64)-1, EXTENT_DIRTY,
                           GFP_NOFS);
@@ -3475,14 +3479,15 @@ int btrfs_relocate_block_group(struct btrfs_root *extent_root, u64 group_start)
         btrfs_wait_ordered_extents(fs_info->tree_root, 0);
 
         while (1) {
-                mutex_lock(&fs_info->cleaner_mutex);
-                btrfs_clean_old_snapshots(fs_info->tree_root);
-                mutex_unlock(&fs_info->cleaner_mutex);
-
                 rc->extents_found = 0;
                 rc->extents_skipped = 0;
 
+                mutex_lock(&fs_info->cleaner_mutex);
+
+                btrfs_clean_old_snapshots(fs_info->tree_root);
                 ret = relocate_block_group(rc);
+
+                mutex_unlock(&fs_info->cleaner_mutex);
                 if (ret < 0) {
                         err = ret;
                         break;
@@ -3530,6 +3535,26 @@ out:
         return err;
 }
 
+static noinline_for_stack int mark_garbage_root(struct btrfs_root *root)
+{
+        struct btrfs_trans_handle *trans;
+        int ret;
+
+        trans = btrfs_start_transaction(root->fs_info->tree_root, 1);
+
+        memset(&root->root_item.drop_progress, 0,
+                sizeof(root->root_item.drop_progress));
+        root->root_item.drop_level = 0;
+        btrfs_set_root_refs(&root->root_item, 0);
+        ret = btrfs_update_root(trans, root->fs_info->tree_root,
+                                &root->root_key, &root->root_item);
+        BUG_ON(ret);
+
+        ret = btrfs_end_transaction(trans, root->fs_info->tree_root);
+        BUG_ON(ret);
+        return 0;
+}
+
 /*
  * recover relocation interrupted by system crash.
  *
@@ -3589,8 +3614,12 @@ int btrfs_recover_relocation(struct btrfs_root *root)
                         fs_root = read_fs_root(root->fs_info,
                                                reloc_root->root_key.offset);
                         if (IS_ERR(fs_root)) {
-                                err = PTR_ERR(fs_root);
-                                goto out;
+                                ret = PTR_ERR(fs_root);
+                                if (ret != -ENOENT) {
+                                        err = ret;
+                                        goto out;
+                                }
+                                mark_garbage_root(reloc_root);
                         }
                 }