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@xxxxxxxxxxxxx
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