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, 62 insertions, 19 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index a4f531047c4..a0d41e713f3 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1378,8 +1378,10 @@ static int setup_bdi(struct btrfs_fs_info *info, struct backing_dev_info *bdi)
 
         err = bdi_register(bdi, NULL, "btrfs-%d",
                                 atomic_inc_return(&btrfs_bdi_num));
-        if (err)
+        if (err) {
+                bdi_destroy(bdi);
                 return err;
+        }
 
         bdi->ra_pages   = default_backing_dev_info.ra_pages;
         bdi->unplug_io_fn       = btrfs_unplug_io_fn;
@@ -1469,9 +1471,12 @@ static int cleaner_kthread(void *arg)
                         break;
 
                 vfs_check_frozen(root->fs_info->sb, SB_FREEZE_WRITE);
-                mutex_lock(&root->fs_info->cleaner_mutex);
-                btrfs_clean_old_snapshots(root);
-                mutex_unlock(&root->fs_info->cleaner_mutex);
+
+                if (!(root->fs_info->sb->s_flags & MS_RDONLY) &&
+                    mutex_trylock(&root->fs_info->cleaner_mutex)) {
+                        btrfs_clean_old_snapshots(root);
+                        mutex_unlock(&root->fs_info->cleaner_mutex);
+                }
 
                 if (freezing(current)) {
                         refrigerator();
@@ -1576,7 +1581,26 @@ struct btrfs_root *open_ctree(struct super_block *sb,
                 err = -ENOMEM;
                 goto fail;
         }
-        INIT_RADIX_TREE(&fs_info->fs_roots_radix, GFP_NOFS);
+
+        ret = init_srcu_struct(&fs_info->subvol_srcu);
+        if (ret) {
+                err = ret;
+                goto fail;
+        }
+
+        ret = setup_bdi(fs_info, &fs_info->bdi);
+        if (ret) {
+                err = ret;
+                goto fail_srcu;
+        }
+
+        fs_info->btree_inode = new_inode(sb);
+        if (!fs_info->btree_inode) {
+                err = -ENOMEM;
+                goto fail_bdi;
+        }
+
+        INIT_RADIX_TREE(&fs_info->fs_roots_radix, GFP_ATOMIC);
         INIT_LIST_HEAD(&fs_info->trans_list);
         INIT_LIST_HEAD(&fs_info->dead_roots);
         INIT_LIST_HEAD(&fs_info->hashers);
@@ -1586,6 +1610,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         spin_lock_init(&fs_info->delalloc_lock);
         spin_lock_init(&fs_info->new_trans_lock);
         spin_lock_init(&fs_info->ref_cache_lock);
+        spin_lock_init(&fs_info->fs_roots_radix_lock);
 
         init_completion(&fs_info->kobj_unregister);
         fs_info->tree_root = tree_root;
@@ -1604,11 +1629,6 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         fs_info->sb = sb;
         fs_info->max_extent = (u64)-1;
         fs_info->max_inline = 8192 * 1024;
-        if (setup_bdi(fs_info, &fs_info->bdi))
-                goto fail_bdi;
-        fs_info->btree_inode = new_inode(sb);
-        fs_info->btree_inode->i_ino = 1;
-        fs_info->btree_inode->i_nlink = 1;
         fs_info->metadata_ratio = 8;
 
         fs_info->thread_pool_size = min_t(unsigned long,
@@ -1620,6 +1640,8 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         sb->s_blocksize = 4096;
         sb->s_blocksize_bits = blksize_bits(4096);
 
+        fs_info->btree_inode->i_ino = BTRFS_BTREE_INODE_OBJECTID;
+        fs_info->btree_inode->i_nlink = 1;
         /*
          * we set the i_size on the btree inode to the max possible int.
          * the real end of the address space is determined by all of
@@ -1638,6 +1660,11 @@ struct btrfs_root *open_ctree(struct super_block *sb,
 
         BTRFS_I(fs_info->btree_inode)->io_tree.ops = &btree_extent_io_ops;
 
+        BTRFS_I(fs_info->btree_inode)->root = tree_root;
+        memset(&BTRFS_I(fs_info->btree_inode)->location, 0,
+               sizeof(struct btrfs_key));
+        BTRFS_I(fs_info->btree_inode)->dummy_inode = 1;
+
         spin_lock_init(&fs_info->block_group_cache_lock);
         fs_info->block_group_cache_tree.rb_node = NULL;
 
@@ -1648,21 +1675,16 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         fs_info->pinned_extents = &fs_info->freed_extents[0];
         fs_info->do_barriers = 1;
 
-        BTRFS_I(fs_info->btree_inode)->root = tree_root;
-        memset(&BTRFS_I(fs_info->btree_inode)->location, 0,
-               sizeof(struct btrfs_key));
-        insert_inode_hash(fs_info->btree_inode);
 
         mutex_init(&fs_info->trans_mutex);
         mutex_init(&fs_info->ordered_operations_mutex);
         mutex_init(&fs_info->tree_log_mutex);
-        mutex_init(&fs_info->drop_mutex);
         mutex_init(&fs_info->chunk_mutex);
         mutex_init(&fs_info->transaction_kthread_mutex);
         mutex_init(&fs_info->cleaner_mutex);
         mutex_init(&fs_info->volume_mutex);
-        mutex_init(&fs_info->tree_reloc_mutex);
         init_rwsem(&fs_info->extent_commit_sem);
+        init_rwsem(&fs_info->subvol_sem);
 
         btrfs_init_free_cluster(&fs_info->meta_alloc_cluster);
         btrfs_init_free_cluster(&fs_info->data_alloc_cluster);
@@ -1941,6 +1963,9 @@ printk("thread pool is %d\n", fs_info->thread_pool_size);
                 }
         }
 
+        ret = btrfs_find_orphan_roots(tree_root);
+        BUG_ON(ret);
+
         if (!(sb->s_flags & MS_RDONLY)) {
                 ret = btrfs_recover_relocation(tree_root);
                 BUG_ON(ret);
@@ -2000,6 +2025,8 @@ fail_iput:
         btrfs_mapping_tree_free(&fs_info->mapping_tree);
 fail_bdi:
         bdi_destroy(&fs_info->bdi);
+fail_srcu:
+        cleanup_srcu_struct(&fs_info->subvol_srcu);
 fail:
         kfree(extent_root);
         kfree(tree_root);
@@ -2263,6 +2290,10 @@ int btrfs_free_fs_root(struct btrfs_fs_info *fs_info, struct btrfs_root *root)
         radix_tree_delete(&fs_info->fs_roots_radix,
                           (unsigned long)root->root_key.objectid);
         spin_unlock(&fs_info->fs_roots_radix_lock);
+
+        if (btrfs_root_refs(&root->root_item) == 0)
+                synchronize_srcu(&fs_info->subvol_srcu);
+
         free_fs_root(root);
         return 0;
 }
@@ -2286,6 +2317,20 @@ static int del_fs_roots(struct btrfs_fs_info *fs_info)
         struct btrfs_root *gang[8];
         int i;
 
+        while (!list_empty(&fs_info->dead_roots)) {
+                gang[0] = list_entry(fs_info->dead_roots.next,
+                                     struct btrfs_root, root_list);
+                list_del(&gang[0]->root_list);
+
+                if (gang[0]->in_radix) {
+                        btrfs_free_fs_root(fs_info, gang[0]);
+                } else {
+                        free_extent_buffer(gang[0]->node);
+                        free_extent_buffer(gang[0]->commit_root);
+                        kfree(gang[0]);
+                }
+        }
+
         while (1) {
                 ret = radix_tree_gang_lookup(&fs_info->fs_roots_radix,
                                              (void **)gang, 0,
@@ -2315,9 +2360,6 @@ int btrfs_cleanup_fs_roots(struct btrfs_fs_info *fs_info)
                 root_objectid = gang[ret - 1]->root_key.objectid + 1;
                 for (i = 0; i < ret; i++) {
                         root_objectid = gang[i]->root_key.objectid;
-                        ret = btrfs_find_dead_roots(fs_info->tree_root,
-                                                    root_objectid);
-                        BUG_ON(ret);
                         btrfs_orphan_cleanup(gang[i]);
                 }
                 root_objectid++;
@@ -2405,6 +2447,7 @@ int close_ctree(struct btrfs_root *root)
         btrfs_mapping_tree_free(&fs_info->mapping_tree);
 
         bdi_destroy(&fs_info->bdi);
+        cleanup_srcu_struct(&fs_info->subvol_srcu);
 
         kfree(fs_info->extent_root);
         kfree(fs_info->tree_root);