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From: Ira Weiny <ira.weiny@intel.com>
To: Boaz Harrosh <boaz@plexistor.com>
Cc: linux-kernel@vger.kernel.org,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	"Darrick J. Wong" <darrick.wong@oracle.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Dave Chinner <david@fromorbit.com>,
	Christoph Hellwig <hch@lst.de>,
	"Theodore Y. Ts'o" <tytso@mit.edu>, Jan Kara <jack@suse.cz>,
	linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 1/5] fs/stat: Define DAX statx attribute
Date: Tue, 22 Oct 2019 09:51:29 -0700	[thread overview]
Message-ID: <20191022165128.GA5432@iweiny-DESK2.sc.intel.com> (raw)
In-Reply-To: <119b57ed-2799-c499-00df-50da80d23612@plexistor.com>

On Tue, Oct 22, 2019 at 02:32:04PM +0300, Boaz Harrosh wrote:
> On 20/10/2019 18:59, 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
> > mode (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
> > 
> > 	DAX (cpu direct access) is a file mode that attempts to minimize
> > 	software cache effects for both I/O and memory mappings of this
> > 	file.  It requires a capable device, a compatible filesystem
> > 	block size, and filesystem opt-in. It generally assumes all
> > 	accesses are via cpu load / store instructions which can
> > 	minimize overhead for small accesses, but adversely affect cpu
> > 	utilization for large transfers. File I/O is done directly
> > 	to/from user-space buffers. While the DAX property tends to
> > 	result in data being transferred synchronously it does not give
> > 	the guarantees of synchronous I/O that data and necessary
> > 	metadata are transferred. Memory mapped I/O may be performed
> > 	with direct mappings that bypass system memory buffering. Again
> > 	while memory-mapped I/O tends to result in data being
> > 	transferred synchronously it does not guarantee synchronous
> > 	metadata updates. A dax file may optionally support being mapped
> > 	with the MAP_SYNC flag which does allow cpu store operations to
> > 	be considered synchronous modulo cpu cache effects.
> > 
> > Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> > ---
> >  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 c38e4c2e1221..59ca360c1ffb 100644
> > --- a/fs/stat.c
> > +++ b/fs/stat.c
> > @@ -77,6 +77,9 @@ int vfs_getattr_nosec(const struct path *path, struct kstat *stat,
> >  	if (IS_AUTOMOUNT(inode))
> >  		stat->attributes |= STATX_ATTR_AUTOMOUNT;
> >  
> > +	if (inode->i_flags & S_DAX)
> 
> Is there a reason not to use IS_DAX(inode) ?

No, just forgot there was a macro when this was written.  Changed.

Thanks,
Ira

> 
> > +		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 7b35e98d3c58..5b0962121ef7 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_DAX			0x00002000 /* [I] File is DAX */
> >  
> >  
> >  #endif /* _UAPI_LINUX_STAT_H */
> > 
> 

  reply	other threads:[~2019-10-22 16:51 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-20 15:59 [PATCH 0/5] Enable per-file/directory DAX operations ira.weiny
2019-10-20 15:59 ` [PATCH 1/5] fs/stat: Define DAX statx attribute ira.weiny
2019-10-22 11:32   ` Boaz Harrosh
2019-10-22 16:51     ` Ira Weiny [this message]
2019-10-20 15:59 ` [PATCH 2/5] fs/xfs: Isolate the physical DAX flag from effective ira.weiny
2019-10-21  0:26   ` Dave Chinner
2019-10-21 17:40     ` Ira Weiny
2019-10-20 15:59 ` [PATCH 3/5] fs/xfs: Separate functionality of xfs_inode_supports_dax() ira.weiny
2019-10-20 15:59 ` [PATCH 4/5] fs/xfs: Clean up DAX support check ira.weiny
2019-10-20 15:59 ` [PATCH 5/5] fs/xfs: Allow toggle of physical DAX flag ira.weiny
2019-10-21  0:45   ` Dave Chinner
2019-10-21 22:49     ` Ira Weiny
2019-10-21 23:46       ` Dave Chinner
2019-11-08 13:12       ` Jan Kara
2019-11-08 13:46         ` Jan Kara
2019-11-08 19:36           ` Ira Weiny
2019-11-11 16:07             ` Jan Kara
2019-11-11 23:54               ` Ira Weiny
2019-10-22 11:21 ` [PATCH 0/5] Enable per-file/directory DAX operations Boaz Harrosh
2019-10-23 13:09   ` Boaz Harrosh
2019-10-23 22:13     ` Dave Chinner
2019-10-24  2:31       ` Boaz Harrosh
2019-10-24  7:34         ` Dave Chinner
2019-10-24 14:05           ` Boaz Harrosh
2019-10-24 21:35             ` Dave Chinner
2019-10-24 23:29               ` Boaz Harrosh
2019-10-25  0:36                 ` Dave Chinner
2019-10-25  1:15                   ` Boaz Harrosh
2019-10-25 20:49                   ` Ira Weiny
2019-10-27 22:10                     ` Dave Chinner
2019-10-31 16:17                       ` Ira Weiny
2019-11-01 22:47                         ` Dave Chinner
2019-11-02  4:25                           ` Dan Williams

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