On Thu, Mar 08, 2018 at 09:15:50AM +0300, Andrei Borzenkov wrote: > 07.03.2018 21:49, Liu Bo пишет: > > Hi, > > > > In the following steps[1], if <parent> on receiver side has got > > changed via 'btrfs property set', then after doing incremental > > updates, receiver gets a different snapshot from what sender has sent. > > > > The reason behind it is that there is no change about file 'foo' in > > the send stream, such that receiver simply creates a snapshot of > > <parent> on its side with nothing to apply from the send stream. > > > > A possible way to avoid this is to check rtransid and ctranid of > > <parent> on receiver side, but I'm not very sure whether the current > > behavior is made deliberately, does anyone have an idea? > > > > Thanks, > > > > -liubo > > > > [1]: > > $ btrfs sub create /mnt/send/sub > > $ touch /mnt/send/sub/foo > > $ btrfs sub snap -r /mnt/send/sub /mnt/send/parent > > > > # send parent out > > $ btrfs send /mnt/send/parent | btrfs receive /mnt/recv/ > > > > # change parent and file under it > > $ btrfs property set -t subvol /mnt/recv/parent ro false > > Is removing the ability to modify read-only property an option? What are > use cases for it? What can it do that "btrfs sub snap read-only > writable" cannot? >
Tbh, I don't know any usecase for that, I just wanted to toggle off the ro bit in order to change something inside <parent>. > > $ truncate -s 4096 /mnt/recv/parent/foo > > > > $ btrfs sub snap -r /mnt/send/sub /mnt/send/update > > $ btrfs send -p /mnt/send/parent /mnt/send/update | btrfs receive /mnt/recv > > > > This should fail right away because /mnt/send/parent is not read-only. > If it does not, this is really a bug. > It's not '/mnt/send/parent', but '/mnt/recv/parent' got changed. Thanks, -liubo > Of course one may go one step further and set /mnt/send/parent read-only > again, then we get this issue. > > > $ ls -l /mnt/send/update > > total 0 > > -rw-r--r-- 1 root root 0 Mar 6 11:13 foo > > > > $ ls -l /mnt/recv/update > > total 0 > > -rw-r--r-- 1 root root 4096 Mar 6 11:14 foo > > > > -- > > 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 > > > -- 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
