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From: Jan Kara <jack@suse.cz>
To: Ira Weiny <ira.weiny@intel.com>
Cc: Jan Kara <jack@suse.cz>,
	linux-ext4@vger.kernel.org,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	"Theodore Y. Ts'o" <tytso@mit.edu>,
	Eric Biggers <ebiggers@kernel.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Dan Williams <dan.j.williams@intel.com>,
	Dave Chinner <david@fromorbit.com>,
	Christoph Hellwig <hch@lst.de>, Jeff Moyer <jmoyer@redhat.com>,
	"Darrick J. Wong" <darrick.wong@oracle.com>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH V3 4/8] fs/ext4: Update ext4_should_use_dax()
Date: Thu, 21 May 2020 12:24:34 +0200	[thread overview]
Message-ID: <20200521102434.GA17431@quack2.suse.cz> (raw)
In-Reply-To: <20200520194050.GF3660833@iweiny-DESK2.sc.intel.com>

On Wed 20-05-20 12:40:50, Ira Weiny wrote:
> On Wed, May 20, 2020 at 03:37:28PM +0200, Jan Kara wrote:
> > On Tue 19-05-20 22:57:49, ira.weiny@intel.com wrote:
> > > From: Ira Weiny <ira.weiny@intel.com>
> > > 
> > > S_DAX should only be enabled when the underlying block device supports
> > > dax.
> > > 
> > > Change ext4_should_use_dax() to check for device support prior to the
> > > over riding mount option.
> > > 
> > > While we are at it change the function to ext4_should_enable_dax() as
> > > this better reflects the ask as well as matches xfs.
> > > 
> > > Reviewed-by: Jan Kara <jack@suse.cz>
> > > Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> > 
> > ...
> > 
> > > @@ -4412,7 +4410,13 @@ static bool ext4_should_use_dax(struct inode *inode)
> > >  		return false;
> > >  	if (ext4_test_inode_flag(inode, EXT4_INODE_VERITY))
> > >  		return false;
> > > -	return true;
> > > +	if (!bdev_dax_supported(inode->i_sb->s_bdev,
> > > +				inode->i_sb->s_blocksize))
> > > +		return false;
> > > +	if (test_opt(inode->i_sb, DAX_ALWAYS))
> > > +		return true;
> > > +
> > > +	return false;
> > >  }
> > 
> > Now that I think about it - shouldn't we rather cache the result of
> > bdev_dax_supported() in sb on mount and then just check the flag here?
> > Because bdev_dax_supported() isn't exactly cheap (it does a lot of checks
> > and mappings, tries to read from the pmem, ...).
> 
> Sounds reasonable.
> 
> Not sure which flags are appropriate.  So add it here?

Yes, sounds good. Thanks!

								Honza

> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 1a3daf2d18ef..0b4db9ce7756 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1979,6 +1979,7 @@ static inline bool ext4_has_incompat_features(struct super_block *sb)
>   */
>  #define EXT4_FLAGS_RESIZING    0
>  #define EXT4_FLAGS_SHUTDOWN    1
> +#define EXT4_FLAGS_BDEV_IS_DAX 2
>  
>  static inline int ext4_forced_shutdown(struct ext4_sb_info *sbi)
>  {
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

  reply	other threads:[~2020-05-21 10:24 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-20  5:57 [PATCH V3 0/8] Enable ext4 support for per-file/directory DAX operations ira.weiny
2020-05-20  5:57 ` [PATCH V3 1/8] fs/ext4: Narrow scope of DAX check in setflags ira.weiny
2020-05-20  5:57 ` [PATCH V3 2/8] fs/ext4: Disallow verity if inode is DAX ira.weiny
2020-05-20  5:57 ` [PATCH V3 3/8] fs/ext4: Change EXT4_MOUNT_DAX to EXT4_MOUNT_DAX_ALWAYS ira.weiny
2020-05-20  5:57 ` [PATCH V3 4/8] fs/ext4: Update ext4_should_use_dax() ira.weiny
2020-05-20 13:37   ` Jan Kara
2020-05-20 19:40     ` Ira Weiny
2020-05-21 10:24       ` Jan Kara [this message]
2020-05-20  5:57 ` [PATCH V3 5/8] fs/ext4: Only change S_DAX on inode load ira.weiny
2020-05-20  5:57 ` [PATCH V3 6/8] fs/ext4: Make DAX mount option a tri-state ira.weiny
2020-05-20  5:57 ` [PATCH V3 7/8] fs/ext4: Introduce DAX inode flag ira.weiny
2020-05-20 14:11   ` Jan Kara
2020-05-20 18:34     ` Ira Weiny
2020-05-20 19:26   ` Andreas Dilger
2020-05-20 20:02     ` Ira Weiny
2020-05-20 20:55       ` Darrick J. Wong
2020-05-21  0:57         ` Andreas Dilger
2020-05-20  5:57 ` [PATCH V3 8/8] Documentation/dax: Update DAX enablement for ext4 ira.weiny

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