On Tue, Jul 24, 2018 at 11:54:04AM +0100, fdman...@kernel.org wrote: > From: Filipe Manana <fdman...@suse.com> > > The more common use case of send involves creating a RO snapshot and then > use it for a send operation. In this case it's not possible to have inodes > in the snapshot that have a link count of zero (inode with an orphan item) > since during snapshot creation we do the orphan cleanup. However, other > less common use cases for send can end up seeing inodes with a link count > of zero and in this case the send operation fails with a ENOENT error > because any attempt to generate a path for the inode, with the purpose > of creating it or updating it at the receiver, fails since there are no > inode reference items. One use case it to use a regular subvolume for > a send operation after turning it to RO mode or turning a RW snapshot > into RO mode and then using it for a send operation. In both cases, if a > file gets all its hard links deleted while there is an open file > descriptor before turning the subvolume/snapshot into RO mode, the send > operation will encounter an inode with a link count of zero and then > fail with errno ENOENT. > > Example using a full send with a subvolume: > > $ mkfs.btrfs -f /dev/sdb > $ mount /dev/sdb /mnt > > $ btrfs subvolume create /mnt/sv1 > $ touch /mnt/sv1/foo > $ touch /mnt/sv1/bar > > # keep an open file descriptor on file bar > $ exec 73</mnt/sv1/bar > $ unlink /mnt/sv1/bar > > # Turn the subvolume to RO mode and use it for a full send, while > # holding the open file descriptor. > $ btrfs property set /mnt/sv1 ro true > > $ btrfs send -f /tmp/full.send /mnt/sv1 > At subvol /mnt/sv1 > ERROR: send ioctl failed with -2: No such file or directory > > Example using an incremental send with snapshots: > > $ mkfs.btrfs -f /dev/sdb > $ mount /dev/sdb /mnt > > $ btrfs subvolume create /mnt/sv1 > $ touch /mnt/sv1/foo > $ touch /mnt/sv1/bar > > $ btrfs subvolume snapshot -r /mnt/sv1 /mnt/snap1 > > $ echo "hello world" >> /mnt/sv1/bar > > $ btrfs subvolume snapshot -r /mnt/sv1 /mnt/snap2 > > # Turn the second snapshot to RW mode and delete file foo while > # holding an open file descriptor on it. > $ btrfs property set /mnt/snap2 ro false > $ exec 73</mnt/snap2/foo > $ unlink /mnt/snap2/foo > > # Set the second snapshot back to RO mode and do an incremental send. > $ btrfs property set /mnt/snap2 ro true > > $ btrfs send -f /tmp/inc.send -p /mnt/snap1 /mnt/snap2 > At subvol /mnt/snap2 > ERROR: send ioctl failed with -2: No such file or directory > > So fix this by ignoring inodes with a link count of zero if we are either > doing a full send or if they do not exist in the parent snapshot (they > are new in the send snapshot), and unlink all paths found in the parent > snapshot when doing an incremental send (and ignoring all other inode > items, such as xattrs and extents). > > A test case for fstests follows soon. > > Reported-by: Martin Wilck <martin.wi...@suse.com> > Signed-off-by: Filipe Manana <fdman...@suse.com>
Added to misc-next, thanks. I did a light review of the overall logic how the ignore_cur_inode is passed around, skipping the orphans and replacing with send_unlink sounds ok to me. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
