On Sat, Nov 4, 2017 at 12:27 PM, Andrei Borzenkov <[email protected]> wrote: > 04.11.2017 10:05, Adam Borowski пишет: >> On Sat, Nov 04, 2017 at 09:26:36AM +0300, Andrei Borzenkov wrote: >>> 04.11.2017 07:49, Adam Borowski пишет: >>>> On Fri, Nov 03, 2017 at 06:15:53PM -0600, Chris Murphy wrote: >>>>> Ancient bug, still seems to be a bug. >>>>> https://bugzilla.redhat.com/show_bug.cgi?id=906591 >>>>> >>>>> The issue is that updatedb by default will not index bind mounts, but >>>>> by default on Fedora and probably other distros, put /home on a >>>>> subvolume and then mount that subvolume which is in effect a bind >>>>> mount. >>>>> >>>>> There's a lot of early discussion in 2013 about it, but then it's >>>>> dropped off the radar as nobody has any ideas how to fix this in >>>>> mlocate. >>>> >>>> I don't see how this would be a bug in btrfs. The same happens if you >>>> bind-mount /home (or individual homes), which is a valid and non-rare >>>> setup. >>> >>> It is the problem *on* btrfs because - as opposed to normal bind mount - >>> those mount points do *not* refer to the same content. >> >> Neither do they refer to in a "normal" bind mount. >> >>> As was commented in mentioned bug report: >>> >>> mount -o subvol=root /dev/sdb1 /root >>> mount -o subvol=foo /dev/sdb1 /root/foo >>> mount -o subvol bar /dev/sdb1 /bar/bar >>> >>> Both /root/foo and /root/bar, will be skipped even though they are not >>> accessible via any other path (on mounted filesystem) >> >> losetup -D >> truncate -s 4G junk >> losetup -f junk >> mkfs.ext4 /dev/loop0 >> mkdir -p foo bar >> mount /dev/loop0 foo >> mkdir foo/bar >> touch foo/fileA foo/bar/fileB >> mount --bind foo/bar bar >> umount foo >> > > Indeed. I can build the same configuration on non-btrfs and updatedb > would skip non-overlapping mounts just as it would on btrfs. It is just > that it is rather more involved on other filesystems (and as you > mentioned this requires top-level to be mounted at some point), while on > btrfs it is much easier to get (and is default on number of distributions). > > So yes, it really appears that updatedb check for duplicated mounts is > wrong in general and needs rethinking.
Yes, even if it's not a Btrfs bug, I think it's useful to get a different set of eyes on this than just the mlocate folks. Maybe it should get posted to fs-devel? -- Chris Murphy -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
