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author | Kaiwen Hu <kevinhu@synology.com> | 2022-03-23 15:10:32 +0800 |
---|---|---|
committer | David Sterba <dsterba@suse.com> | 2022-03-24 17:50:57 +0100 |
commit | 60021bd754c6ca0addc6817994f20290a321d8d6 (patch) | |
tree | b3f7df29132a39858d8cab9ef6a8340c92b9067f /fs/btrfs | |
parent | a7d16d9a07bbcb7dcd5214a1bea75c808830bc0d (diff) | |
download | linux-stable-60021bd754c6ca0addc6817994f20290a321d8d6.tar.gz linux-stable-60021bd754c6ca0addc6817994f20290a321d8d6.tar.bz2 linux-stable-60021bd754c6ca0addc6817994f20290a321d8d6.zip |
btrfs: prevent subvol with swapfile from being deleted
A subvolume with an active swapfile must not be deleted otherwise it
would not be possible to deactivate it.
After the subvolume is deleted, we cannot swapoff the swapfile in this
deleted subvolume because the path is unreachable. The swapfile is
still active and holding references, the filesystem cannot be unmounted.
The test looks like this:
mkfs.btrfs -f $dev > /dev/null
mount $dev $mnt
btrfs sub create $mnt/subvol
touch $mnt/subvol/swapfile
chmod 600 $mnt/subvol/swapfile
chattr +C $mnt/subvol/swapfile
dd if=/dev/zero of=$mnt/subvol/swapfile bs=1K count=4096
mkswap $mnt/subvol/swapfile
swapon $mnt/subvol/swapfile
btrfs sub delete $mnt/subvol
swapoff $mnt/subvol/swapfile # failed: No such file or directory
swapoff --all
unmount $mnt # target is busy.
To prevent above issue, we simply check that whether the subvolume
contains any active swapfile, and stop the deleting process. This
behavior is like snapshot ioctl dealing with a swapfile.
CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Robbie Ko <robbieko@synology.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Kaiwen Hu <kevinhu@synology.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs')
-rw-r--r-- | fs/btrfs/inode.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index b976f757571f..5aab6af88349 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -4487,6 +4487,13 @@ int btrfs_delete_subvolume(struct inode *dir, struct dentry *dentry) dest->root_key.objectid); return -EPERM; } + if (atomic_read(&dest->nr_swapfiles)) { + spin_unlock(&dest->root_item_lock); + btrfs_warn(fs_info, + "attempt to delete subvolume %llu with active swapfile", + root->root_key.objectid); + return -EPERM; + } root_flags = btrfs_root_flags(&dest->root_item); btrfs_set_root_flags(&dest->root_item, root_flags | BTRFS_ROOT_SUBVOL_DEAD); @@ -11110,8 +11117,23 @@ static int btrfs_swap_activate(struct swap_info_struct *sis, struct file *file, * set. We use this counter to prevent snapshots. We must increment it * before walking the extents because we don't want a concurrent * snapshot to run after we've already checked the extents. + * + * It is possible that subvolume is marked for deletion but still not + * removed yet. To prevent this race, we check the root status before + * activating the swapfile. */ + spin_lock(&root->root_item_lock); + if (btrfs_root_dead(root)) { + spin_unlock(&root->root_item_lock); + + btrfs_exclop_finish(fs_info); + btrfs_warn(fs_info, + "cannot activate swapfile because subvolume %llu is being deleted", + root->root_key.objectid); + return -EPERM; + } atomic_inc(&root->nr_swapfiles); + spin_unlock(&root->root_item_lock); isize = ALIGN_DOWN(inode->i_size, fs_info->sectorsize); |