From: Ira Weiny <ira.weiny@intel.com>
To: Jan Kara <jack@suse.cz>
Cc: 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: Wed, 20 May 2020 12:40:50 -0700 [thread overview]
Message-ID: <20200520194050.GF3660833@iweiny-DESK2.sc.intel.com> (raw)
In-Reply-To: <20200520133728.GD30597@quack2.suse.cz>
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?
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)
{
next prev parent reply other threads:[~2020-05-20 19:40 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 [this message]
2020-05-21 10:24 ` Jan Kara
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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