On Fri, Aug 01, 2014 at 02:49:10PM +1000, Dave Chinner wrote: > On Fri, Aug 01, 2014 at 12:02:41PM +0800, Eryu Guan wrote: > > On Fri, Aug 01, 2014 at 10:21:59AM +1000, Dave Chinner wrote: > > > On Thu, Jul 31, 2014 at 06:52:37PM +0800, Eryu Guan wrote: > > > > When testing with lvm, a previous btrfsck run could change df output > > > > from something like > > > > > > > > /dev/mapper/rhel_hp--dl388eg8--01-testlv1 btrfs 15728640 900 13602172 1% /mnt/btrfs > > > > > > > > to > > > > > > > > /dev/dm-3 btrfs 15728640 900 13602172 1% /mnt/btrfs > > > > > > I don't follow you. Why would running btrfsck change the name of the > > > device? If the filesystem is umounted and mounted again, then the > > > device could change, but btrfsck should not be not doing the > > > unmount/mount, and so unless the TEST_DEV/SCRATCH_DEV is changing > > > the output of df should be identical... > > > > > > So before we change the _fs_type() code, can you explain exactly > > > how, when and why the device name is changing to me? > > > > Assume that we have two btrfs filesystems, kernel is 3.16.0-rc4+ > > > > [root@hp-dl388eg8-01 btrfs-progs]# btrfs fi show > > Label: none uuid: 1aba7da5-ce2b-4af0-a716-db732abc60b2 > > Total devices 1 FS bytes used 384.00KiB > > devid 1 size 15.00GiB used 2.04GiB path /dev/mapper/rhel_hp--dl388eg8--01-testlv1 > > > > Label: none uuid: 26ff4f12-f6d9-4cbc-aae2-57febeefde37 > > Total devices 2 FS bytes used 112.00KiB > > devid 1 size 15.00GiB used 2.03GiB path /dev/mapper/rhel_hp--dl388eg8--01-testlv2 > > devid 2 size 15.00GiB used 2.01GiB path /dev/mapper/rhel_hp--dl388eg8--01-testlv3 > > > > Btrfs v3.14.2 > > > > And testlv1 was mounted at /mnt/btrfs > > > > [root@hp-dl388eg8-01 btrfs-progs]# df -TP /mnt/btrfs > > Filesystem Type 1024-blocks Used Available Capacity Mounted on > > /dev/mapper/rhel_hp--dl388eg8--01-testlv1 btrfs 15728640 512 13602560 1% /mnt/btrfs > > > > Now run btrfsck on testlv2, btrfsck will scan all btrfs devices and > > somehow change the device name. > > > > [root@hp-dl388eg8-01 btrfs-progs]# btrfsck /dev/mapper/rhel_hp--dl388eg8--01-testlv2 >/dev/null 2>&1 > > > > # device name changed in df output and btrfs fi show output > > [root@hp-dl388eg8-01 btrfs-progs]# df -TP /mnt/btrfs > > Filesystem Type 1024-blocks Used Available Capacity Mounted on > > /dev/dm-3 btrfs 15728640 512 13602560 1% /mnt/btrfs > > [root@hp-dl388eg8-01 btrfs-progs]# btrfs fi show > > Label: none uuid: 1aba7da5-ce2b-4af0-a716-db732abc60b2 > > Total devices 1 FS bytes used 384.00KiB > > devid 1 size 15.00GiB used 2.04GiB path /dev/dm-3 > > > > Label: none uuid: 26ff4f12-f6d9-4cbc-aae2-57febeefde37 > > Total devices 2 FS bytes used 112.00KiB > > devid 1 size 15.00GiB used 2.03GiB path /dev/mapper/rhel_hp--dl388eg8--01-testlv2 > > devid 2 size 15.00GiB used 2.01GiB path /dev/mapper/rhel_hp--dl388eg8--01-testlv3 > > > > Btrfs v3.14.2 > > > > This only happens when btrfsck a btrfs with multiple devices, so this > > only affects xfstests run on btrfs with SCRATCH_DEV_POOL set to lvm > > lvs. > > > > Maybe this is a bug of btrfs-progs and we should fix it there? > > Yes, that smells of a btrfs-progs bug. If your /etc/mtab a link to > /proc/mounts? If not, does the contents change when you run btrfsck, > and does the problem go away when you replace /etc/mtab with a link > to /proc/mounts? /etc/mtab is a symlink to /proc/self/mounts, so does /proc/mounts [root@hp-dl388eg8-01 btrfs-progs]# ls -l /etc/mtab lrwxrwxrwx. 1 root root 17 Sep 22 2013 /etc/mtab -> /proc/self/mounts [root@hp-dl388eg8-01 btrfs-progs]# ls -l /proc/mounts lrwxrwxrwx. 1 root root 11 Aug 1 00:59 /proc/mounts -> self/mounts And the device name also changed in /proc/mounts [root@hp-dl388eg8-01 btrfs-progs]# grep btrfs /proc/mounts /dev/dm-3 /mnt/btrfs btrfs rw,seclabel,relatime,space_cache 0 0 Thanks, Eryu > > Cheers, > > Dave. > -- > Dave Chinner > david@xxxxxxxxxxxxx > -- > To unsubscribe from this list: send the line "unsubscribe fstests" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe fstests" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
