Hi all, enclosed you can find a patch which permits to remove a volume via the rmdir(2) syscall by an ordinary user. The rules for a subvolume removal are the same ones of a directory: - the user must have the write permission on the parent directory - the subvolume must be empty
The mains differences between calling rmdir(2) on a subvolume and calling the
BTRFS_IOC_SNAP_DESTROY ioctl are:
- rmdir(2) requires the subvolume to be empty (the user has to empty the
subvolume before removing it, like the rm -rf command does)
- rmdir(2) is a synchronous operation (instead BTRFS_IOC_SNAP_DESTROY works
in background)
The previous statements have the following (nice) consequences:
- the CAP_ADMIN capability is not required anymore to remove a subvolume.
BTRFS_IOC_SNAP_DESTROY requires CAP_ADMIN because the subvolume removal is
performed in background so it would not be possible to return an error if
the user has not the privilege of removing a file.
- when the rmdir(2) syscall returns the space is really freed, and there is
no necessity to create another API to wait the ends of the
BTRFS_IOC_SNAP_DESTROY ioctl.
The only advantage of the BTRFS_IOC_SNAP_DESTROY ioctl is its greater speed
in removing a not empty subvolume.
I simplify the code respect my previous post, removing a un-needed call to the
function may_destroy_subvol().
You can pull the code from the branch named "rmdir-subvolume" of the following
repository:
http://cassiopea.homelinux.net/git/btrfs-unstable.git
As usual, comments are welcome
Regards
G.Baroncelli
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index f08427c..0df2fb0 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2944,6 +2944,84 @@ int btrfs_unlink_subvol(struct btrfs_trans_handle *trans,
return 0;
}
+static noinline int btrfs_snap_destroy(struct inode *dir,
+ struct dentry *dentry)
+{
+
+ struct inode *inode;
+ struct btrfs_root *root = BTRFS_I(dir)->root;
+ struct btrfs_root *dest = NULL;
+ struct btrfs_trans_handle *trans;
+ int ret;
+ int err = 0;
+
+ if (IS_ERR(dentry)) {
+ err = PTR_ERR(dentry);
+ goto out;
+ }
+
+ if (!dentry->d_inode) {
+ err = -ENOENT;
+ goto out;
+ }
+
+ inode = dentry->d_inode;
+ if (inode->i_ino != BTRFS_FIRST_FREE_OBJECTID) {
+ err = -EINVAL;
+ goto out;
+ }
+
+ dest = BTRFS_I(inode)->root;
+
+ down_write(&root->fs_info->subvol_sem);
+
+ /* remove this check because the directory is empty.
+ * err = may_destroy_subvol(dest);
+ * if (err)
+ * goto out_up_write;
+ */
+
+ trans = btrfs_start_transaction(root, 0);
+ if (IS_ERR(trans)) {
+ err = PTR_ERR(trans);
+ goto out_up_write;
+ }
+ trans->block_rsv = &root->fs_info->global_block_rsv;
+
+ ret = btrfs_unlink_subvol(trans, root, dir,
+ dest->root_key.objectid,
+ dentry->d_name.name,
+ dentry->d_name.len);
+ BUG_ON(ret);
+
+ btrfs_record_root_in_trans(trans, dest);
+
+ memset(&dest->root_item.drop_progress, 0,
+ sizeof(dest->root_item.drop_progress));
+ dest->root_item.drop_level = 0;
+ btrfs_set_root_refs(&dest->root_item, 0);
+
+ if (!xchg(&dest->orphan_item_inserted, 1)) {
+ ret = btrfs_insert_orphan_item(trans,
+ root->fs_info->tree_root,
+ dest->root_key.objectid);
+ BUG_ON(ret);
+ }
+
+ ret = btrfs_commit_transaction(trans, root);
+ BUG_ON(ret);
+ inode->i_flags |= S_DEAD;
+out_up_write:
+ up_write(&root->fs_info->subvol_sem);
+ if (!err) {
+ shrink_dcache_sb(root->fs_info->sb);
+ btrfs_invalidate_inodes(dest);
+ /*d_delete(dentry);*/
+ }
+out:
+ return err;
+}
+
static int btrfs_rmdir(struct inode *dir, struct dentry *dentry)
{
struct inode *inode = dentry->d_inode;
@@ -2952,10 +3030,12 @@ static int btrfs_rmdir(struct inode *dir, struct dentry
*dentry)
struct btrfs_trans_handle *trans;
unsigned long nr = 0;
- if (inode->i_size > BTRFS_EMPTY_DIR_SIZE ||
- inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)
+ if (inode->i_size > BTRFS_EMPTY_DIR_SIZE)
return -ENOTEMPTY;
+ if (inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)
+ return btrfs_snap_destroy(dir, dentry);
+
trans = __unlink_start_trans(dir, dentry);
if (IS_ERR(trans))
return PTR_ERR(trans);
--
gpg key@ keyserver.linux.it: Goffredo Baroncelli (ghigo) <kreijackATinwind.it>
Key fingerprint = 4769 7E51 5293 D36C 814E C054 BF04 F161 3DC5 0512
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