Eryu Guan
2014-Aug-01 04:02 UTC
Re: [PATCH v2] common: get fs type again using device canonical name in _fs_type
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? If we decide to take this patch, I'll put more details in commit log in v3. Thanks, Eryu> > Cheers, > > Dave. > -- > Dave Chinner > david@fromorbit.com-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html