Re: [PATCH 3/3] btrfs-progs: use BTRFS_SCAN_BACKUP_SB flag in btrfs_scan_one_device

[Anand Jain <Anand.Jain@oracle.com>]

just for the record, this patch also fixes the following 2 issues..

  sdc contains primary-SB of ext4 and backup SB of btrfs

# blkid /dev/sdc
/dev/sdc: UUID="4450e281-db04-4736-a03e-1ce6deda74f3" TYPE="ext4"
#

# btrfs-show-super -i 1 /dev/sdc
superblock: bytenr=67108864, device=/dev/sdc
::

----
# ~/before/btrfs dev scan
Scanning for Btrfs filesystems
ERROR: device scan failed '/dev/sdc' - Invalid argument

# btrfs dev scan
Scanning for Btrfs filesystems
----

-----
# ~/before/btrfs fi show
::

Label: none  uuid: aa8b3f0c-3ade-490a-a35d-dd62dbd9cc07
	Total devices 2 FS bytes used 796.00KB
	devid    2 size 59.99GB used 2.01GB path /dev/sdc
	*** Some devices missing
::
Btrfs v0.20-rc1-235-gdd21bc1
#


# btrfs fi show
Label: none  uuid: 0d690e00-a34f-4c6b-9660-c6b1b6684ecc
	Total devices 1 FS bytes used 28.00KB
	devid    1 size 59.99GB used 2.04GB path /dev/sdb

Label: none  uuid: fa08122d-832f-4f32-87ee-58eb9380d5da
	Total devices 2 FS bytes used 796.00KB
	devid    2 size 48.23GB used 2.01GB path /dev/sde
	devid    1 size 44.99GB used 2.03GB path /dev/sdd

Btrfs v0.20-rc1-238-g5d571b4-dirty
-----

Thanks, Anand


On 03/13/2013 07:46 PM, Anand Jain wrote:
>
>
> Thanks Eric and David.
>
>   I have sent out V3 patch-set which will disable access
>   to backup super-block unless requested by the user.
>
>   here below are some test cases and results before and
>   after this fix.. which finds the patch works awesome.
>
>
> --------
> the original problem which all this started..
>
> mkfs.btrfs /dev/sdb -f && yes| mkfs.ext4 /dev/sdb && mount /dev/sdb /ext4
> ~/before/mkfs.btrfs -f /dev/sdc /dev/sdd (run twice)
> ~/before/mkfs.btrfs -f /dev/sdc /dev/sdd
> ::
> ERROR: unable to scan the device '/dev/sdb' - Device or resource busy
> ERROR: unable to scan the device '/dev/sdb' - Device or resource busy
> adding device /dev/sdd id 2
> fs created label (null) on /dev/sdc
>          nodesize 4096 leafsize 4096 sectorsize 4096 size 3.11GB
>
>
> after the fix.
>
> # mkfs.btrfs -f /dev/sdc /dev/sdd
>
> WARNING! - Btrfs v0.20-rc1-238-g170881a-dirty IS EXPERIMENTAL
> WARNING! - see http://btrfs.wiki.kernel.org before using
>
> adding device /dev/sdd id 2
> fs created label (null) on /dev/sdc
>      nodesize 4096 leafsize 4096 sectorsize 4096 size 104.98GB
> Btrfs v0.20-rc1-238-g170881a-dirty
> -------------
>
> # umount /ext4
>
> # mkfs.btrfs /dev/sdb /dev/sdc -f && wipefs /dev/sdb
>
> There is an existing bug..
>
> # ~/before/btrfs check /dev/sdc --repair
> enabling repair mode
> warning, device 1 is missing
> warning, device 1 is missing
> warning devid 1 not found already
> Checking filesystem on /dev/sdc
> UUID: e03c477d-b696-46c1-bf79-43b8b8454f11
> checking extents
> checking fs roots
> checking root refs
> btrfs: extent-tree.c:2553: btrfs_reserve_extent: Assertion `!(ret)' failed.
> Aborted (core dumped)
> #
>
> and its still there even after this patch :-)
>
> # btrfs check /dev/sdc --repair
> enabling repair mode
> warning, device 1 is missing
> warning, device 1 is missing
> warning devid 1 not found already
> Checking filesystem on /dev/sdc
> UUID: e03c477d-b696-46c1-bf79-43b8b8454f11
> checking extents
> checking fs roots
> checking root refs
> btrfs: extent-tree.c:2553: btrfs_reserve_extent: Assertion `!(ret)' failed.
> Aborted (core dumped)
>
> -------------------------
>
>
> # mkfs.btrfs /dev/sdb /dev/sdc -f && yes|mkfs.ext4 /dev/sdb
>
> without the fix
> # ~/before/btrfs restore -o /dev/sdb ~/tmp
> ERROR: device scan failed '/dev/sdb' - Invalid argument
> ERROR: device scan failed '/dev/sdb' - Invalid argument
> Root objectid is 5
>
> with the fix
>
> # btrfs restore -o /dev/sdb ~/tmp
> No valid Btrfs found on /dev/sdb
> Could not open root, trying backup super
> Root objectid is 5
>
> now I say to use sb backup 1..
>
> # btrfs restore -u 1 -o /dev/sdb ~/tmp
> Root objectid is 5
> # echo $?
> 0
>
> --------------
>
> # mkfs.btrfs /dev/sdb /dev/sdc -f && yes|mkfs.ext4 /dev/sdb
>
> # ~/before/btrfs check /dev/sdc --repair
> enabling repair mode
> ERROR: device scan failed '/dev/sdb' - Invalid argument
> ERROR: device scan failed '/dev/sdb' - Invalid argument
> Checking filesystem on /dev/sdc
> UUID: 5dc5c663-eeea-4ec2-b8fe-170157f5d68d
> checking extents
> checking fs roots
> checking root refs
> found 28672 bytes used err is 0
> total csum bytes: 0
> total tree bytes: 28672
> total fs tree bytes: 8192
> btree space waste bytes: 22420
> file data blocks allocated: 0
>   referenced 0
> Btrfs v0.20-rc1-235-gdd21bc1
>
> # mkfs.btrfs /dev/sdb /dev/sdc -f && yes|mkfs.ext4 /dev/sdb
>
> since now new code doesn't read backup SB of devid1
> it hits the earlier known bug.
>
> # btrfs check /dev/sdc --repair
> enabling repair mode
> warning, device 1 is missing
> warning, device 1 is missing
> warning devid 1 not found already
> Checking filesystem on /dev/sdc
> UUID: daa0dc6d-35b6-43ab-8333-894710a5b917
> checking extents
> checking fs roots
> checking root refs
> btrfs: extent-tree.c:2553: btrfs_reserve_extent: Assertion `!(ret)' failed.
> Aborted (core dumped)
>
> So user would need to fix the devid1 first.
>
> # btrfs check /dev/sdb --repair
> enabling repair mode
> No valid Btrfs found on /dev/sdb
>
> # btrfs check -s 1 /dev/sdb --repair
> using SB copy 1, bytenr 67108864
> enabling repair mode
> Checking filesystem on /dev/sdb
> UUID: daa0dc6d-35b6-43ab-8333-894710a5b917
> checking extents
> checking fs roots
> checking root refs
> found 28672 bytes used err is 0
> total csum bytes: 0
> total tree bytes: 28672
> total fs tree bytes: 8192
> btree space waste bytes: 22420
> file data blocks allocated: 0
>   referenced 0
> Btrfs v0.20-rc1-238-g170881a-dirty
>
> # btrfs check /dev/sdc --repair
> enabling repair mode
> warning, device 1 is missing
> warning, device 1 is missing
> warning devid 1 not found already
> Checking filesystem on /dev/sdc
> UUID: daa0dc6d-35b6-43ab-8333-894710a5b917
> checking extents
> checking fs roots
> checking root refs
> btrfs: extent-tree.c:2553: btrfs_reserve_extent: Assertion `!(ret)' failed.
> Aborted (core dumped)
>
> Need to write back the backup SB to primary SB.
> IMO when -s 1 was given it had the chance to fix
> primary.. this can be fixed later.
>
> # ./btrfs-select-super -s 1 /dev/sdb
> using SB copy 1, bytenr 67108864
> ERROR: device scan failed '/dev/sdb' - Invalid argument
>
> # btrfs check /dev/sdc --repair
> enabling repair mode
> Checking filesystem on /dev/sdc
> UUID: daa0dc6d-35b6-43ab-8333-894710a5b917
> checking extents
> checking fs roots
> checking root refs
> found 28672 bytes used err is 0
> total csum bytes: 0
> total tree bytes: 28672
> total fs tree bytes: 8192
> btree space waste bytes: 22420
> file data blocks allocated: 0
>   referenced 0
> Btrfs v0.20-rc1-238-g170881a-dirty
> ---------------------------------------------------------------
>
>
> I am not sure if I have a wipe -a working for btrfs,
> so I would clean using dd.
>
> # dd if=/dev/zero bs=1 count=8 of=/dev/sdb seek=$((64*1024+64))
> 8+0 records in
> 8+0 records out
> 8 bytes (8 B) copied, 0.000324503 s, 24.7 kB/s
>
> # dd if=/dev/zero bs=1 count=8 of=/dev/sdb seek=$((64*1024*1024+64))
> 8+0 records in
> 8+0 records out
> 8 bytes (8 B) copied, 0.000364635 s, 21.9 kB/s
>
> # dd if=/dev/zero bs=1 count=8 of=/dev/sdb seek=$((256*1024*1024*1024+64))
> dd: `/dev/sdb': cannot seek: Invalid argument
> 0+0 records in
> 0+0 records out
> 0 bytes (0 B) copied, 0.000430846 s, 0.0 kB/s
>
> This behavior is same before and after the patch.
>
> # btrfs check /dev/sdb
> No valid Btrfs found on /dev/sdb
> # btrfs check /dev/sdb -s 1
> using SB copy 1, bytenr 67108864
> No valid Btrfs found on /dev/sdb
> # btrfs check /dev/sdb -s 2
> using SB copy 2, bytenr 274877906944
> No valid Btrfs found on /dev/sdb
> #
> ------------------------
>
>   # mkfs.btrfs /dev/sdb /dev/sdc -f && mount /dev/sdc /btrfs
>
>   # dd if=/dev/zero bs=1 count=8 of=/dev/sdb seek=$((64*1024+64))
>   # dd if=/dev/zero bs=1 count=8 of=/dev/sdb seek=$((64*1024*1024+64))
>   # dd if=/dev/zero bs=1 count=8 of=/dev/sdb
> seek=$((256*1024*1024*1024+64))
>
> # mkfs.btrfs /dev/sdb
>
> WARNING! - Btrfs v0.20-rc1-238-g170881a-dirty IS EXPERIMENTAL
> WARNING! - see http://btrfs.wiki.kernel.org before using
>
> /dev/sdb is mounted
>
>
> # umount /btrfs
>
> # mkfs.btrfs /dev/sdb
>
> WARNING! - Btrfs v0.20-rc1-238-g170881a-dirty IS EXPERIMENTAL
> WARNING! - see http://btrfs.wiki.kernel.org before using
>
> /dev/sdb appears to contain an existing filesystem (btrfs).
> Use the -f option to force overwrite.
> #
>
> -------------------------
>
>
> # mkfs.btrfs /dev/sdd /dev/sde -f
>
> WARNING! - Btrfs v0.20-rc1-238-g170881a-dirty IS EXPERIMENTAL
> WARNING! - see http://btrfs.wiki.kernel.org before using
>
> adding device /dev/sde id 2
> fs created label (null) on /dev/sdd
>      nodesize 4096 leafsize 4096 sectorsize 4096 size 93.22GB
> Btrfs v0.20-rc1-238-g170881a-dirty
> # mount /dev/sde /btrfs
> # umount /btrfs
> # dd if=/dev/zero bs=1 count=8 of=/dev/sde seek=$((64*1024+64))
> 8+0 records in
> 8+0 records out
> 8 bytes (8 B) copied, 0.0149415 s, 0.5 kB/s
>
> remove /dev/sdd
>
> # x="0 0 3 0"
> # echo "scsi remove-single-device $x" > /proc/scsi/scsi
> # lsscsi
> [0:0:0:0]    disk    Sun      boot1            V1.0  /dev/sda
> [0:0:2:0]    disk    Sun      boot3            V1.0  /dev/sdc
> [0:0:4:0]    disk    Sun      boot5            V1.0  /dev/sde
> [0:1:0:0]    disk    SEAGATE  ST914602SSUN146G 0603  -
> [0:1:1:0]    disk    SEAGATE  ST914602SSUN146G 0603  -
> [0:3:0:0]    enclosu ADAPTEC  Virtual SGPIO  0 0001  -
>
>
> # btrfs check /dev/sde
> No valid Btrfs found on /dev/sde
>
> # btrfs check /dev/sde -s 1
> using SB copy 1, bytenr 67108864
> warning, device 1 is missing
> warning, device 1 is missing
> warning devid 1 not found already
> Checking filesystem on /dev/sde
> UUID: fa08122d-832f-4f32-87ee-58eb9380d5da
> checking extents
> checking fs roots
> checking root refs
> found 815104 bytes used err is 0
> total csum bytes: 0
> total tree bytes: 28672
> total fs tree bytes: 8192
> btree space waste bytes: 21476
> file data blocks allocated: 786432
>   referenced 786432
> Btrfs v0.20-rc1-238-g170881a-dirty
>
> # ./btrfs-select-super -s 1 /dev/sde
> using SB copy 1, bytenr 67108864
> ERROR: device scan failed '/dev/sdc' - Invalid argument
> warning, device 1 is missing
> warning, device 1 is missing
> warning devid 1 not found already
>
> # btrfs check /dev/sde
> warning, device 1 is missing
> warning, device 1 is missing
> warning devid 1 not found already
> Checking filesystem on /dev/sde
> UUID: fa08122d-832f-4f32-87ee-58eb9380d5da
> checking extents
> checking fs roots
> checking root refs
> found 815104 bytes used err is 0
> total csum bytes: 0
> total tree bytes: 28672
> total fs tree bytes: 8192
> btree space waste bytes: 21476
> file data blocks allocated: 786432
>   referenced 786432
> Btrfs v0.20-rc1-238-g170881a-dirty
> #
> ---------------
>
>
> Thanks, Anand
>
>
> On 03/12/2013 02:16 AM, David Sterba wrote:
>> On Mon, Mar 11, 2013 at 10:03:46AM -0500, Eric Sandeen wrote:
>>> IMHO, nothing should be checking the backup superblocks unless
>>> explicitly
>>> told to.
>>
>> That's the whole point I believe.
>>
>> update the infrastructure, every SB access looks to the first copy
>> unless told by command line options.
>>
>>
>> david
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