linux-kernel - Re: [PATCH 0/6] block atomic writes for XFS

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Date: Tue, 13 Feb 2024 08:41:10 +0000
From: John Garry <john.g.garry@...cle.com>
To: "Ritesh Harjani (IBM)" <ritesh.list@...il.com>, hch@....de,
        djwong@...nel.org, viro@...iv.linux.org.uk, brauner@...nel.org,
        dchinner@...hat.com, jack@...e.cz, chandan.babu@...cle.com
Cc: martin.petersen@...cle.com, linux-kernel@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        tytso@....edu, jbongio@...gle.com, ojaswin@...ux.ibm.com
Subject: Re: [PATCH 0/6] block atomic writes for XFS

On 13/02/2024 07:45, Ritesh Harjani (IBM) wrote:
> John Garry <john.g.garry@...cle.com> writes:
> 
>> This series expands atomic write support to filesystems, specifically
>> XFS. Since XFS rtvol supports extent alignment already, support will
>> initially be added there. When XFS forcealign feature is merged, then we
>> can similarly support atomic writes for a non-rtvol filesystem.
>>
>> Flag FS_XFLAG_ATOMICWRITES is added as an enabling flag for atomic writes.
>>
>> For XFS rtvol, support can be enabled through xfs_io command:
>> $xfs_io -c "chattr +W" filename
>> $xfs_io -c "lsattr -v" filename
>> [realtime, atomic-writes] filename
> 
> Hi John,
> 
> I first took your block atomic write patch series [1] and then applied this
> series on top. I also compiled xfsprogs with chattr atomic write support from [2].
> 
> [1]: https://lore.kernel.org/linux-nvme/20240124113841.31824-1-john.g.garry@oracle.com/T/#m4ad28b480a8e12eb51467e17208d98ca50041ff2
> [2]: https://github.com/johnpgarry/xfsprogs-dev/commits/atomicwrites/
> 
> 
> But while setting +W attr, I see an Invalid argument error. Is there
> anything I need to do first?
> 
> root@...ntu:~# /root/xt/xfsprogs-dev/io/xfs_io -c "chattr +W" /mnt1/test/f1
> xfs_io: cannot set flags on /mnt1/test/f1: Invalid argument
> 
> root@...ntu:~# /root/xt/xfsprogs-dev/io/xfs_io -c "lsattr -v" /mnt1/test/f1
> [realtime] /mnt1/test/f1

Can you provide your full steps?

I'm doing something like:

# /mkfs.xfs -r rtdev=/dev/sdb,extsize=16k -d rtinherit=1 /dev/sda
meta-data=/dev/sda               isize=512    agcount=4, agsize=22400 blks
          =                       sectsz=512   attr=2, projid32bit=1
          =                       crc=1        finobt=1, sparse=1, rmapbt=0
          =                       reflink=0    bigtime=1 inobtcount=1 
nrext64=0
data     =                       bsize=4096   blocks=89600, imaxpct=25
          =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
log      =internal log           bsize=4096   blocks=16384, version=2
          =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =/dev/sdb               extsz=16384  blocks=89600, rtextents=22400
# mount /dev/sda mnt -o rtdev=/dev/sdb
[    5.553482] XFS (sda): EXPERIMENTAL atomic writes feature in use. Use 
at your own risk!
[    5.556752] XFS (sda): Mounting V5 Filesystem 
6e0820e6-4d44-4c3e-89f2-21b4d4480f88
[    5.602315] XFS (sda): Ending clean mount
#
# touch mnt/file
# /xfs_io -c "lsattr -v" mnt/file
[realtime] mnt/file
#
#
# /xfs_io -c "chattr +W" mnt/file
# /xfs_io -c "lsattr -v" mnt/file
[realtime, atomic-writes] mnt/file

And then we can check limits:

# /test-statx -a /root/mnt/file
dump_statx results=9fff
   Size: 0               Blocks: 0          IO Block: 16384   regular file
Device: 08:00           Inode: 131         Links: 1
Access: (0644/-rw-r--r--)  Uid:     0   Gid:     0
Access: 2024-02-13 08:31:51.962900974+0000
Modify: 2024-02-13 08:31:51.962900974+0000
Change: 2024-02-13 08:31:51.969900974+0000
  Birth: 2024-02-13 08:31:51.962900974+0000
stx_attributes_mask=0x603070
         STATX_ATTR_WRITE_ATOMIC set
         unit min: 4096
         unit max: 16384
         segments max: 1
Attributes: 0000000000400000 (........ ........ ........ ........ 
....... .?-..... ..--.... .---....)
#
#

Does xfs_io have a statx function? If so, I can add support for atomic 
writes for statx there. In the meantime, that test-statx code is also on 
my branch, and can be run on the block device file (to sanity check that 
the rtvol device supports atomic writes).

Thanks,
John