Btrfs: set dead flag on the right root when destroying snapshot

We were setting the BTRFS_ROOT_SUBVOL_DEAD flag on the root of the
parent of our target snapshot, instead of setting it in the target
snapshot's root.

This is easy to observe by running the following scenario:

    mkfs.btrfs -f /dev/sdd
    mount /dev/sdd /mnt

    btrfs subvolume create /mnt/first_subvol
    btrfs subvolume snapshot -r /mnt /mnt/mysnap1

    btrfs subvolume delete /mnt/first_subvol
    btrfs subvolume snapshot -r /mnt /mnt/mysnap2

    btrfs send -p /mnt/mysnap1 /mnt/mysnap2 -f /tmp/send.data

The send command failed because the send ioctl returned -EPERM.
A test case for xfstests follows.

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 6 insertions, 6 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 362720a3fea2..38f2169b73a4 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2312,16 +2312,16 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,
          * again is not run concurrently.
          */
         spin_lock(&dest->root_item_lock);
-        root_flags = btrfs_root_flags(&root->root_item);
-        if (root->send_in_progress == 0) {
-                btrfs_set_root_flags(&root->root_item,
+        root_flags = btrfs_root_flags(&dest->root_item);
+        if (dest->send_in_progress == 0) {
+                btrfs_set_root_flags(&dest->root_item,
                                 root_flags | BTRFS_ROOT_SUBVOL_DEAD);
                 spin_unlock(&dest->root_item_lock);
         } else {
                 spin_unlock(&dest->root_item_lock);
                 btrfs_warn(root->fs_info,
                         "Attempt to delete subvolume %llu during send",
-                        root->root_key.objectid);
+                        dest->root_key.objectid);
                 err = -EPERM;
                 goto out_dput;
         }
@@ -2416,8 +2416,8 @@ out_up_write:
 out_unlock:
         if (err) {
                 spin_lock(&dest->root_item_lock);
-                root_flags = btrfs_root_flags(&root->root_item);
-                btrfs_set_root_flags(&root->root_item,
+                root_flags = btrfs_root_flags(&dest->root_item);
+                btrfs_set_root_flags(&dest->root_item,
                                 root_flags & ~BTRFS_ROOT_SUBVOL_DEAD);
                 spin_unlock(&dest->root_item_lock);
         }