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From: ira.weiny@intel.com
To: linux-kernel@vger.kernel.org
Cc: Ira Weiny <ira.weiny@intel.com>, Jan Kara <jack@suse.cz>,
	"Darrick J . Wong" <darrick.wong@oracle.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Dan Williams <dan.j.williams@intel.com>,
	Dave Chinner <david@fromorbit.com>,
	Christoph Hellwig <hch@lst.de>,
	"Theodore Y. Ts'o" <tytso@mit.edu>,
	linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: [PATCH V4 04/13] fs/stat: Define DAX statx attribute
Date: Thu, 20 Feb 2020 16:41:25 -0800	[thread overview]
Message-ID: <20200221004134.30599-5-ira.weiny@intel.com> (raw)
In-Reply-To: <20200221004134.30599-1-ira.weiny@intel.com>

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 */
-- 
2.21.0


  parent reply	other threads:[~2020-02-21  0:42 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-21  0:41 [PATCH V4 00/13] Enable per-file/per-directory DAX operations V4 ira.weiny
2020-02-21  0:41 ` [PATCH V4 01/13] fs/xfs: Remove unnecessary initialization of i_rwsem ira.weiny
2020-02-21  1:26   ` Dave Chinner
2020-02-27 17:52     ` Ira Weiny
2020-02-21  0:41 ` [PATCH V4 02/13] fs/xfs: Clarify lockdep dependency for xfs_isilocked() ira.weiny
2020-02-21  1:34   ` Dave Chinner
2020-02-21 23:00     ` Ira Weiny
2020-02-21  0:41 ` [PATCH V4 03/13] fs: Remove unneeded IS_DAX() check ira.weiny
2020-02-21  1:42   ` Dave Chinner
2020-02-21 23:04     ` Ira Weiny
2020-02-21 17:42   ` Christoph Hellwig
2020-02-21  0:41 ` ira.weiny [this message]
2020-02-21  0:41 ` [PATCH V4 05/13] fs/xfs: Isolate the physical DAX flag from enabled ira.weiny
2020-02-21  0:41 ` [PATCH V4 06/13] fs/xfs: Create function xfs_inode_enable_dax() ira.weiny
2020-02-22  0:28   ` Darrick J. Wong
2020-02-23 15:07     ` Ira Weiny
2020-02-21  0:41 ` [PATCH V4 07/13] fs: Add locking for a dynamic address space operations state ira.weiny
2020-02-21 17:44   ` Christoph Hellwig
2020-02-21 22:44     ` Dave Chinner
2020-02-21 23:26       ` Dan Williams
2020-02-24 17:56       ` Christoph Hellwig
2020-02-25  0:09         ` Dave Chinner
2020-02-25 17:36           ` Christoph Hellwig
2020-02-25 19:37             ` Jeff Moyer
2020-02-26  9:28               ` Jonathan Halliday
2020-02-26 11:31                 ` Jan Kara
2020-02-26 11:56                   ` Jonathan Halliday
2020-02-26 16:10                 ` Ira Weiny
2020-02-26 16:46                 ` Dan Williams
2020-02-26 17:20                   ` Jan Kara
2020-02-26 17:54                     ` Dan Williams
2020-02-25 21:03             ` Ira Weiny
2020-02-26 11:17           ` Jan Kara
2020-02-26 15:57             ` Ira Weiny
2020-02-22  0:33   ` Darrick J. Wong
2020-02-23 15:03     ` Ira Weiny
2020-02-21  0:41 ` [PATCH V4 08/13] fs: Prevent DAX state change if file is mmap'ed ira.weiny
2020-02-21  0:41 ` [PATCH V4 09/13] fs/xfs: Add write aops lock to xfs layer ira.weiny
2020-02-22  0:31   ` Darrick J. Wong
2020-02-23 15:04     ` Ira Weiny
2020-02-24  0:34   ` Dave Chinner
2020-02-24 19:57     ` Ira Weiny
2020-02-24 22:32       ` Dave Chinner
2020-02-25 21:12         ` Ira Weiny
2020-02-25 22:59           ` Dave Chinner
2020-02-26 18:02             ` Ira Weiny
2020-02-21  0:41 ` [PATCH V4 10/13] fs/xfs: Clean up locking in dax invalidate ira.weiny
2020-02-21 17:45   ` Christoph Hellwig
2020-02-21 18:06     ` Ira Weiny
2020-02-21  0:41 ` [PATCH V4 11/13] fs/xfs: Allow toggle of effective DAX flag ira.weiny
2020-02-21  0:41 ` [PATCH V4 12/13] fs/xfs: Remove xfs_diflags_to_linux() ira.weiny
2020-02-21  0:41 ` [PATCH V4 13/13] Documentation/dax: Update Usage section ira.weiny
2020-02-26 22:48 ` [PATCH V4 00/13] Enable per-file/per-directory DAX operations V4 Jeff Moyer
2020-02-27  2:43   ` Ira Weiny

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