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From: Dave Chinner <david@fromorbit.com>
To: ira.weiny@intel.com
Cc: linux-kernel@vger.kernel.org, Jan Kara <jack@suse.cz>,
	"Darrick J . Wong" <darrick.wong@oracle.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Christoph Hellwig <hch@lst.de>,
	"Theodore Y. Ts'o" <tytso@mit.edu>,
	Jeff Moyer <jmoyer@redhat.com>,
	linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH V6 3/8] fs/stat: Define DAX statx attribute
Date: Wed, 8 Apr 2020 09:47:49 +1000	[thread overview]
Message-ID: <20200407234749.GE24067@dread.disaster.area> (raw)
In-Reply-To: <20200407182958.568475-4-ira.weiny@intel.com>

On Tue, Apr 07, 2020 at 11:29:53AM -0700, ira.weiny@intel.com wrote:
> From: Ira Weiny <ira.weiny@intel.com>
> 
> In order for users to determine if a file is currently operating in DAX
> state (effective DAX).  Define a statx attribute value and set that
> attribute if the effective DAX flag is set.
> 
> To go along with this we propose the following addition to the statx man
> page:
> 
> STATX_ATTR_DAX
> 
> 	The file is in the DAX (cpu direct access) state.  DAX state
> 	attempts to minimize software cache effects for both I/O and
> 	memory mappings of this file.  It requires a file system which
> 	has been configured to support DAX.
> 
> 	DAX generally assumes all accesses are via cpu load / store
> 	instructions which can minimize overhead for small accesses, but
> 	may adversely affect cpu utilization for large transfers.
> 
> 	File I/O is done directly to/from user-space buffers and memory
> 	mapped I/O may be performed with direct memory mappings that
> 	bypass kernel page cache.
> 
> 	While the DAX property tends to result in data being transferred
> 	synchronously, it does not give the same guarantees of O_SYNC
> 	where data and the necessary metadata are transferred together.
> 
> 	A DAX file may support being mapped with the MAP_SYNC flag,
> 	which enables a program to use CPU cache flush instructions to
> 	persist CPU store operations without an explicit fsync(2).  See
> 	mmap(2) for more information.
> 
> Reviewed-by: Jan Kara <jack@suse.cz>
> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> 
> ---
> Changes from V2:
> 	Update man page text with comments from Darrick, Jan, Dan, and
> 	Dave.
> ---
>  fs/stat.c                 | 3 +++
>  include/uapi/linux/stat.h | 1 +
>  2 files changed, 4 insertions(+)
> 
> diff --git a/fs/stat.c b/fs/stat.c
> index 030008796479..894699c74dde 100644
> --- a/fs/stat.c
> +++ b/fs/stat.c
> @@ -79,6 +79,9 @@ int vfs_getattr_nosec(const struct path *path, struct kstat *stat,
>  	if (IS_AUTOMOUNT(inode))
>  		stat->attributes |= STATX_ATTR_AUTOMOUNT;
>  
> +	if (IS_DAX(inode))
> +		stat->attributes |= STATX_ATTR_DAX;
> +
>  	if (inode->i_op->getattr)
>  		return inode->i_op->getattr(path, stat, request_mask,
>  					    query_flags);
> diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
> index ad80a5c885d5..e5f9d5517f6b 100644
> --- a/include/uapi/linux/stat.h
> +++ b/include/uapi/linux/stat.h
> @@ -169,6 +169,7 @@ struct statx {
>  #define STATX_ATTR_ENCRYPTED		0x00000800 /* [I] File requires key to decrypt in fs */
>  #define STATX_ATTR_AUTOMOUNT		0x00001000 /* Dir: Automount trigger */
>  #define STATX_ATTR_VERITY		0x00100000 /* [I] Verity protected file */
> +#define STATX_ATTR_DAX			0x00002000 /* [I] File is DAX */
>  
>  
>  #endif /* _UAPI_LINUX_STAT_H */

Looks fine. Man page text seems ok, too.

Reviewed-by: Dave Chinner <dchinner@redhat.com>
-- 
Dave Chinner
david@fromorbit.com

  reply	other threads:[~2020-04-07 23:47 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-07 18:29 [PATCH V6 0/8] Enable per-file/per-directory DAX operations V6 ira.weiny
2020-04-07 18:29 ` [PATCH V6 1/8] fs/xfs: Remove unnecessary initialization of i_rwsem ira.weiny
2020-04-07 23:46   ` Dave Chinner
2020-04-07 18:29 ` [PATCH V6 2/8] fs: Remove unneeded IS_DAX() check ira.weiny
2020-04-09  7:31   ` Christoph Hellwig
2020-04-09 14:57     ` Ira Weiny
2020-04-07 18:29 ` [PATCH V6 3/8] fs/stat: Define DAX statx attribute ira.weiny
2020-04-07 23:47   ` Dave Chinner [this message]
2020-04-07 18:29 ` [PATCH V6 4/8] fs/xfs: Make DAX mount option a tri-state ira.weiny
2020-04-07 23:59   ` Dave Chinner
2020-04-08  0:09     ` Ira Weiny
2020-04-08  0:48       ` Dave Chinner
2020-04-09 15:03         ` Ira Weiny
2020-04-07 18:29 ` [PATCH V6 5/8] fs/xfs: Create function xfs_inode_enable_dax() ira.weiny
2020-04-08  0:05   ` Dave Chinner
2020-04-08  0:13     ` Ira Weiny
2020-04-07 18:29 ` [PATCH V6 6/8] fs/xfs: Combine xfs_diflags_to_linux() and xfs_diflags_to_iflags() ira.weiny
2020-04-08  2:08   ` Dave Chinner
2020-04-08 17:09     ` Ira Weiny
2020-04-08 21:02       ` Dave Chinner
2020-04-08 21:28         ` Dan Williams
2020-04-08 22:10           ` Ira Weiny
2020-04-08 23:58           ` Dave Chinner
2020-04-09  0:22             ` Ira Weiny
2020-04-09 12:41               ` Christoph Hellwig
2020-04-09 20:49                 ` Ira Weiny
2020-04-08 22:07         ` Ira Weiny
2020-04-08 23:21           ` Dave Chinner
2020-04-09  0:12             ` Ira Weiny
2020-04-09  0:30               ` Darrick J. Wong
2020-04-09 15:29                 ` Ira Weiny
2020-04-09 16:59                   ` Darrick J. Wong
2020-04-09 17:17                     ` Jan Kara
2020-04-09 20:54                     ` Ira Weiny
2020-04-09  0:49               ` Dave Chinner
2020-04-09 12:40                 ` Christoph Hellwig
2020-04-10  0:27                   ` Dave Chinner
2020-04-07 18:29 ` [PATCH V6 7/8] fs/xfs: Change xfs_ioctl_setattr_dax_invalidate() to xfs_ioctl_dax_check() ira.weiny
2020-04-08  2:23   ` Dave Chinner
2020-04-08  9:58     ` Jan Kara
2020-04-08 21:09       ` Dave Chinner
2020-04-08 22:26         ` Ira Weiny
2020-04-08 23:48           ` Dave Chinner
2020-04-09 12:28             ` Christoph Hellwig
2020-04-08 15:37   ` Darrick J. Wong
2020-04-08 18:13     ` Ira Weiny
2020-04-16  5:39   ` [fs/xfs] 857c9841f8: xfstests.xfs.046.fail kernel test robot
2020-04-07 18:29 ` [PATCH V6 8/8] Documentation/dax: Update Usage section ira.weiny

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