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From: "Kani, Toshi" <toshi.kani@hpe.com>
To: "jack@suse.cz" <jack@suse.cz>
Cc: "tytso@mit.edu" <tytso@mit.edu>,
	"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"adilger.kernel@dilger.ca" <adilger.kernel@dilger.ca>,
	"linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>
Subject: Re: [PATCH 1/2] ext4, dax: update dax check to skip journal inode
Date: Wed, 12 Sep 2018 15:47:12 +0000	[thread overview]
Message-ID: <92faf51ac89e62dcd67e39cc66eef60966d1263c.camel@hpe.com> (raw)
In-Reply-To: <20180912092422.GA7782@quack2.suse.cz>

On Wed, 2018-09-12 at 11:24 +0200, Jan Kara wrote:
> On Tue 11-09-18 09:42:45, Toshi Kani wrote:
> > Ext4 mount path calls ext4_iget() to obtain the journal inode.  This
> > inode does not support DAX, and 'ext4_da_aops' needs to be set.  It
> > currently works for the DAX mount case because ext4_iget() always set
> > 'ext4_da_aops' to any regular files.
> > 
> >   ext4_fill_super
> >     ext4_load_journal
> >       ext4_get_journal_inode
> >         ext4_iget
> > 
> > In preparation to fix ext4_iget() to set 'ext4_dax_aops' for DAX files,
> > update ext4_should_use_dax() to return false for the journal inode.
> > 
> > Fixes: 5f0663bb4a64f588f0a2dd6d1be68d40f9af0086
> > Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
> > Cc: Jan Kara <jack@suse.cz>
> > Cc: Dan Williams <dan.j.williams@intel.com>
> > Cc: "Theodore Ts'o" <tytso@mit.edu>
> > Cc: Andreas Dilger <adilger.kernel@dilger.ca>
> The journal inode is similar to any other 'system' inode we have in ext4.
> We don't really expect any of the address space operations to be called for
> it because we don't use page cache with these inodes. Very similar
> situation is with e.g. quota files. So to me it seems this patch is not
> really necessary. Or did you observe any bad effects without this patch?

Yes, without this change, mount fails with the error below.  I believe
.bmap operation in ext4_da_aops is necessary for this case.

  jbd2_journal_init_inode: Cannot locate journal superblock
(pmem1): Could not load journal inode

> That being said I agree that it would be a good cleanup to define something
> like ext4_is_system_inode() and disable DAX for these inodes just because
> they are special. But I don't see a need for this as a part of your fix.

Is there other system inode we need to check for?


Linux-nvdimm mailing list

  reply	other threads:[~2018-09-12 15:47 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-11 15:42 [PATCH 0/2] fix sync to flush processor cache for ext4 DAX files Toshi Kani
2018-09-11 15:42 ` [PATCH 1/2] ext4, dax: update dax check to skip journal inode Toshi Kani
2018-09-11 17:59   ` Dan Williams
2018-09-11 18:11     ` Kani, Toshi
2018-09-12  9:24   ` Jan Kara
2018-09-12 15:47     ` Kani, Toshi [this message]
2018-09-12 16:20       ` Jan Kara
2018-09-12 16:52         ` Kani, Toshi
2018-09-11 15:42 ` [PATCH 2/2] ext4, dax: set ext4_dax_aops for dax files Toshi Kani
2018-09-11 18:15   ` Dan Williams
2018-09-11 18:41     ` Kani, Toshi
2018-09-12  9:31     ` Jan Kara
2018-09-12 16:08       ` Kani, Toshi
2018-09-12 16:41         ` Dan Williams

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