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From: Eric Sandeen <sandeen@sandeen.net>
To: Bill O'Donnell <billodo@redhat.com>
Cc: "Darrick J. Wong" <djwong@kernel.org>,
	Bill O'Donnell <bodonnel@redhat.com>,
	linux-xfs@vger.kernel.org
Subject: Re: [PATCH] xfs: dax: facilitate EXPERIMENTAL warning for dax=inode case
Date: Thu, 26 Aug 2021 18:43:44 -0500	[thread overview]
Message-ID: <9a9d54bd-42a5-45c7-38b2-dec12c49defc@sandeen.net> (raw)
In-Reply-To: <20210826220841.jsdlbquqq55cetnu@redhat.com>

On 8/26/21 5:08 PM, Bill O'Donnell wrote:
> On Thu, Aug 26, 2021 at 01:16:22PM -0500, Eric Sandeen wrote:
>>
>> On 8/26/21 1:09 PM, Darrick J. Wong wrote:
>>> On Thu, Aug 26, 2021 at 12:30:12PM -0500, Bill O'Donnell wrote:
>>
>>>> @@ -1584,7 +1586,7 @@ xfs_fs_fill_super(
>>>>    	if (xfs_has_crc(mp))
>>>>    		sb->s_flags |= SB_I_VERSION;
>>>> -	if (xfs_has_dax_always(mp)) {
>>>> +	if (xfs_has_dax_always(mp) || xfs_has_dax_inode(mp)) {
>>>
>>> Er... can't this be done without burning another feature bit by:
>>>
>>> 	if (xfs_has_dax_always(mp) || (!xfs_has_dax_always(mp) &&
>>> 				       !xfs_has_dax_never(mp))) {
>>> 		...
>>> 		xfs_warn(mp, "DAX IS EXPERIMENTAL");
>>> 	}
>>
>> changing this conditional in this way will also fail dax=inode mounts on
>> reflink-capable (i.e. default) filesystems, no?
> 
> Correct. My original patch tests fine, and still handles the reflink and dax
> incompatibility. The new suggested logic is problematic.
> -Bill

I think that both your proposed patch and Darrick's suggestion have this problem.

"mount -o dax=inode" makes your new xfs_has_dax_inode(mp) true, and in that
conditional, if the filesystem has reflink enabled, mount fails:

# mkfs.xfs -f /dev/pmem0p1
meta-data=/dev/pmem0p1           isize=512    agcount=4, agsize=4194304 blks
          =                       sectsz=4096  attr=2, projid32bit=1
          =                       crc=1        finobt=1, sparse=1, rmapbt=0
          =                       reflink=1    bigtime=0 inobtcount=0
data     =                       bsize=4096   blocks=16777216, imaxpct=25
          =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
log      =internal log           bsize=4096   blocks=8192, version=2
          =                       sectsz=4096  sunit=1 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0

# mount -o dax=inode /dev/pmem0p1 /mnt/test
mount: wrong fs type, bad option, bad superblock on /dev/pmem0p1,
        missing codepage or helper program, or other error

        In some cases useful info is found in syslog - try
        dmesg | tail or so.

# dmesg | tail -n 2
[  192.691733] XFS (pmem0p1): DAX enabled. Warning: EXPERIMENTAL, use at your own risk
[  192.700300] XFS (pmem0p1): DAX and reflink cannot be used together!

  reply	other threads:[~2021-08-26 23:43 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-26 17:30 Bill O'Donnell
2021-08-26 18:09 ` Darrick J. Wong
2021-08-26 18:14   ` Bill O'Donnell
2021-08-26 18:16   ` Eric Sandeen
2021-08-26 22:08     ` Bill O'Donnell
2021-08-26 23:43       ` Eric Sandeen [this message]
2021-08-27 14:03         ` Bill O'Donnell
2021-08-27 14:18           ` Eric Sandeen
2021-08-27 14:25             ` Bill O'Donnell
2021-08-27 15:35               ` Eric Sandeen
2021-08-27 15:41                 ` Bill O'Donnell
2021-08-30 15:55   ` Bill O'Donnell

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