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From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Jan Kara <jack@suse.cz>
Cc: ira.weiny@intel.com, linux-kernel@vger.kernel.org,
	linux-xfs@vger.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>,
	"Theodore Y. Ts'o" <tytso@mit.edu>,
	Jeff Moyer <jmoyer@redhat.com>,
	linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-api@vger.kernel.org
Subject: Re: [PATCH V11 11/11] fs/xfs: Update xfs_ioctl_setattr_dax_invalidate()
Date: Wed, 3 Jun 2020 10:03:44 -0700
Message-ID: <20200603170344.GO2162697@magnolia> (raw)
In-Reply-To: <20200603101024.GG19165@quack2.suse.cz>

On Wed, Jun 03, 2020 at 12:10:24PM +0200, Jan Kara wrote:
> On Tue 02-06-20 10:23:53, Darrick J. Wong wrote:
> > On Tue, Apr 28, 2020 at 01:11:38PM -0700, Darrick J. Wong wrote:
> > > > -out_unlock:
> > > > -	xfs_iunlock(ip, XFS_MMAPLOCK_EXCL | XFS_IOLOCK_EXCL);
> > > > -	return error;
> > > > +	if ((mp->m_flags & XFS_MOUNT_DAX_ALWAYS) ||
> > > > +	    (mp->m_flags & XFS_MOUNT_DAX_NEVER))
> > > > +		return;
> > > >  
> > > > +	if (((fa->fsx_xflags & FS_XFLAG_DAX) &&
> > > > +	    !(ip->i_d.di_flags2 & XFS_DIFLAG2_DAX)) ||
> > > > +	    (!(fa->fsx_xflags & FS_XFLAG_DAX) &&
> > > > +	     (ip->i_d.di_flags2 & XFS_DIFLAG2_DAX)))
> > > > +		d_mark_dontcache(inode);
> > 
> > Now that I think about this further, are we /really/ sure that we want
> > to let unprivileged userspace cause inode evictions?
> 
> You have to have an equivalent of write access to the file to be able to
> trigger d_mark_dontcache(). So you can e.g. delete it.  Or you could
> fadvise / madvise regarding its page cache. I don't see the ability to push
> inode out of cache as stronger than the abilities you already have...

<nod> Ok.  I just had one last bout of paranoia, but I think it'll be
fine. :)

--D

> 								Honza
> -- 
> Jan Kara <jack@suse.com>
> SUSE Labs, CR

      reply index

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-28  0:21 [PATCH V11 00/11] XFS - Enable per-file/per-directory DAX operations V11 ira.weiny
2020-04-28  0:21 ` [PATCH V11 01/11] fs/xfs: Remove unnecessary initialization of i_rwsem ira.weiny
2020-04-28  0:21 ` [PATCH V11 02/11] fs: Remove unneeded IS_DAX() check in io_is_direct() ira.weiny
2020-04-28  0:21 ` [PATCH V11 03/11] fs/stat: Define DAX statx attribute ira.weiny
2020-04-28  0:21 ` [PATCH V11 04/11] Documentation/dax: Update Usage section ira.weiny
2020-04-28 20:27   ` Darrick J. Wong
2020-04-28 20:53     ` Ira Weiny
2020-04-28 21:12       ` Darrick J. Wong
2020-04-28 22:21   ` [PATCH V11.1] " ira.weiny
2020-04-29  2:21     ` Randy Dunlap
2020-04-29  4:30       ` Ira Weiny
2020-04-29  4:33     ` [PATCH V11.2] " ira.weiny
2020-04-29  5:47       ` Randy Dunlap
2020-04-28  0:21 ` [PATCH V11 05/11] fs/xfs: Change XFS_MOUNT_DAX to XFS_MOUNT_DAX_ALWAYS ira.weiny
2020-04-28  0:21 ` [PATCH V11 06/11] fs/xfs: Make DAX mount option a tri-state ira.weiny
2020-04-28 20:08   ` Darrick J. Wong
2020-04-28  0:21 ` [PATCH V11 07/11] fs/xfs: Create function xfs_inode_should_enable_dax() ira.weiny
2020-04-28  0:21 ` [PATCH V11 08/11] fs/xfs: Combine xfs_diflags_to_linux() and xfs_diflags_to_iflags() ira.weiny
2020-04-28  0:21 ` [PATCH V11 09/11] fs: Lift XFS_IDONTCACHE to the VFS layer ira.weiny
2020-04-28 20:06   ` Darrick J. Wong
2020-04-28  0:21 ` [PATCH V11 10/11] fs: Introduce DCACHE_DONTCACHE ira.weiny
2020-04-28 13:04   ` Jan Kara
2020-04-28 20:09   ` Darrick J. Wong
2020-04-28  0:21 ` [PATCH V11 11/11] fs/xfs: Update xfs_ioctl_setattr_dax_invalidate() ira.weiny
2020-04-28 20:11   ` Darrick J. Wong
2020-06-02 17:23     ` Darrick J. Wong
2020-06-02 23:15       ` Ira Weiny
2020-06-03 10:10       ` Jan Kara
2020-06-03 17:03         ` Darrick J. Wong [this message]

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