4.1-stable review patch. If anyone has any objections, please let me know.
------------------ From: Omar Sandoval <[email protected]> commit 64ad6c488975d7516230cf7849190a991fd615ae upstream. Since commit bafc9b754f75 ("vfs: More precise tests in d_invalidate"), mounted subvolumes can be deleted because d_invalidate() won't fail. However, we run into problems when we attempt to delete the default subvolume while it is mounted as the root filesystem: # btrfs subvol list / ID 257 gen 306 top level 5 path rootvol ID 267 gen 334 top level 5 path snap1 # btrfs subvol get-default / ID 267 gen 334 top level 5 path snap1 # btrfs inspect-internal rootid / 267 # mount -o subvol=/ /dev/vda1 /mnt # btrfs subvol del /mnt/snap1 Delete subvolume (no-commit): '/mnt/snap1' ERROR: cannot delete '/mnt/snap1' - Operation not permitted # findmnt / findmnt: can't read /proc/mounts: No such file or directory # ls /proc # Markus reported that this same scenario simply led to a kernel oops. This happens because in btrfs_ioctl_snap_destroy(), we call d_invalidate() before we check may_destroy_subvol(), which means that we detach the submounts and drop the dentry before erroring out. Instead, we should only invalidate the dentry once the deletion has succeeded. Additionally, the shrink_dcache_sb() isn't necessary; d_invalidate() will prune the dcache for the deleted subvolume. Fixes: bafc9b754f75 ("vfs: More precise tests in d_invalidate") Reported-by: Markus Schauler <[email protected]> Signed-off-by: Omar Sandoval <[email protected]> Signed-off-by: Chris Mason <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- fs/btrfs/ioctl.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -2413,8 +2413,6 @@ static noinline int btrfs_ioctl_snap_des goto out_unlock_inode; } - d_invalidate(dentry); - down_write(&root->fs_info->subvol_sem); err = may_destroy_subvol(dest); @@ -2508,7 +2506,7 @@ out_up_write: out_unlock_inode: mutex_unlock(&inode->i_mutex); if (!err) { - shrink_dcache_sb(root->fs_info->sb); + d_invalidate(dentry); btrfs_invalidate_inodes(dest); d_delete(dentry); ASSERT(dest->send_in_progress == 0); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
