btrfs: protect snapshots from deleting during send

[firefly-linux-kernel-4.4.55.git] / fs / btrfs / send.c

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 484aacac2c89dd0cb7af90c1975712f4db245c9d..c76400dda4df1d686cd9780465e4e4a2c9f4bc89 100644 (file)
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -5518,7 +5518,7 @@ long btrfs_ioctl_send(struct file *mnt_file, void __user *arg_)
 
        /*
         * The subvolume must remain read-only during send, protect against
-        * making it RW.
+        * making it RW. This also protects against deletion.
         */
        spin_lock(&send_root->root_item_lock);
        send_root->send_in_progress++;
@@ -5578,6 +5578,15 @@ long btrfs_ioctl_send(struct file *mnt_file, void __user *arg_)
        }
 
        sctx->send_root = send_root;
+       /*
+        * Unlikely but possible, if the subvolume is marked for deletion but
+        * is slow to remove the directory entry, send can still be started
+        */
+       if (btrfs_root_dead(sctx->send_root)) {
+               ret = -EPERM;
+               goto out;
+       }
+
        sctx->clone_roots_cnt = arg->clone_sources_count;
 
        sctx->send_max_size = BTRFS_SEND_BUF_SIZE;
@@ -5667,7 +5676,8 @@ long btrfs_ioctl_send(struct file *mnt_file, void __user *arg_)
 
                spin_lock(&sctx->parent_root->root_item_lock);
                sctx->parent_root->send_in_progress++;
-               if (!btrfs_root_readonly(sctx->parent_root)) {
+               if (!btrfs_root_readonly(sctx->parent_root) ||
+                               btrfs_root_dead(sctx->parent_root)) {
                        spin_unlock(&sctx->parent_root->root_item_lock);
                        srcu_read_unlock(&fs_info->subvol_srcu, index);
                        ret = -EPERM;