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From: Ira Weiny <ira.weiny@intel.com>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Jeff Moyer <jmoyer@redhat.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Dave Chinner <david@fromorbit.com>,
	Christoph Hellwig <hch@lst.de>,
	"Theodore Y. Ts'o" <tytso@mit.edu>, Jan Kara <jack@suse.cz>,
	linux-ext4 <linux-ext4@vger.kernel.org>,
	linux-xfs <linux-xfs@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH v3 00/12] Enable per-file/directory DAX operations V3
Date: Thu, 20 Feb 2020 08:49:57 -0800
Message-ID: <20200220164957.GB20772@iweiny-DESK2.sc.intel.com> (raw)
In-Reply-To: <20200220163024.GV9506@magnolia>

On Thu, Feb 20, 2020 at 08:30:24AM -0800, Darrick J. Wong wrote:
> On Thu, Feb 20, 2020 at 08:20:28AM -0800, Ira Weiny wrote:
> > On Tue, Feb 18, 2020 at 03:54:30PM -0800, 'Ira Weiny' wrote:
> > > On Tue, Feb 18, 2020 at 09:22:58AM -0500, Jeff Moyer wrote:
> > > > Ira Weiny <ira.weiny@intel.com> writes:
> > > > > If my disassembly of read_pages is correct it looks like readpage is null which
> > > > > makes sense because all files should be IS_DAX() == true due to the mount option...
> > > > >
> > > > > But tracing code indicates that the patch:
> > > > >
> > > > > 	fs: remove unneeded IS_DAX() check
> > > > >
> > > > > ... may be the culprit and the following fix may work...
> > > > >
> > > > > diff --git a/mm/filemap.c b/mm/filemap.c
> > > > > index 3a7863ba51b9..7eaf74a2a39b 100644
> > > > > --- a/mm/filemap.c
> > > > > +++ b/mm/filemap.c
> > > > > @@ -2257,7 +2257,7 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
> > > > >         if (!count)
> > > > >                 goto out; /* skip atime */
> > > > >  
> > > > > -       if (iocb->ki_flags & IOCB_DIRECT) {
> > > > > +       if (iocb->ki_flags & IOCB_DIRECT || IS_DAX(inode)) {
> > > > >                 struct file *file = iocb->ki_filp;
> > > > >                 struct address_space *mapping = file->f_mapping;
> > > > >                 struct inode *inode = mapping->host;
> > > > 
> > > > Well, you'll have to up-level the inode variable instantiation,
> > > > obviously.  That solves this particular issue.
> > > 
> > > Well...  This seems to be a random issue.  I've had BMC issues with
> > > my server most of the day...  But even with this patch I still get the failure
> > > in read_pages().  :-/
> > > 
> > > And I have gotten it to both succeed and fail with qemu...  :-/
> > 
> > ... here is the fix.  I made the change in xfs_diflags_to_linux() early on with
> > out factoring in the flag logic changes we have agreed upon...
> > 
> > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> > index 62d9f622bad1..d592949ad396 100644
> > --- a/fs/xfs/xfs_ioctl.c
> > +++ b/fs/xfs/xfs_ioctl.c
> > @@ -1123,11 +1123,11 @@ xfs_diflags_to_linux(
> >                 inode->i_flags |= S_NOATIME;
> >         else
> >                 inode->i_flags &= ~S_NOATIME;
> > -       if (xflags & FS_XFLAG_DAX)
> > +
> > +       if (xfs_inode_enable_dax(ip))
> >                 inode->i_flags |= S_DAX;
> >         else
> >                 inode->i_flags &= ~S_DAX;
> > -
> >  }
> > 
> > But the one thing which tripped me up, and concerns me, is we have 2 functions
> > which set the inode flags.
> > 
> > xfs_diflags_to_iflags()
> > xfs_diflags_to_linux()
> > 
> > xfs_diflags_to_iflags() is geared toward initialization but logically they do
> > the same thing.  I see no reason to keep them separate.  Does anyone?
> > 
> > Based on this find, the discussion on behavior in this thread, and the comments
> > from Dave I'm reworking the series because the flag check/set functions have
> > all changed and I really want to be as clear as possible with both the patches
> > and the resulting code.[*]  So v4 should be out today including attempting to
> > document what we have discussed here and being as clear as possible on the
> > behavior.  :-D
> > 
> > Thanks so much for testing this!
> > 
> > Ira
> > 
> > [*] I will probably throw in a patch to remove xfs_diflags_to_iflags() as I
> > really don't see a reason to keep it.
> > 
> 
> I prefer you keep the one in xfs_iops.c since ioctls are a higher level
> function than general inode operations.

Makes sense.  Do you prefer the xfs_diflags_to_iflags() name as well?

Ira

> 
> --D

  reply index

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-08 19:34 ira.weiny
2020-02-08 19:34 ` [PATCH v3 01/12] fs/stat: Define DAX statx attribute ira.weiny
2020-02-08 19:34 ` [PATCH v3 02/12] fs/xfs: Isolate the physical DAX flag from effective ira.weiny
2020-02-08 19:34 ` [PATCH v3 03/12] fs/xfs: Separate functionality of xfs_inode_supports_dax() ira.weiny
2020-02-11  5:47   ` Dave Chinner
2020-02-11 16:13     ` Ira Weiny
2020-02-08 19:34 ` [PATCH v3 04/12] fs/xfs: Clean up DAX support check ira.weiny
2020-02-11  5:57   ` Dave Chinner
2020-02-11 16:28     ` Ira Weiny
2020-02-11 20:38       ` Dave Chinner
2020-02-08 19:34 ` [PATCH v3 05/12] fs: remove unneeded IS_DAX() check ira.weiny
2020-02-11  5:34   ` Dave Chinner
2020-02-11 16:38     ` Ira Weiny
2020-02-11 20:41       ` Dave Chinner
2020-02-12 16:04         ` Ira Weiny
2020-02-08 19:34 ` [PATCH v3 06/12] fs/xfs: Check if the inode supports DAX under lock ira.weiny
2020-02-11  6:16   ` Dave Chinner
2020-02-11 17:55     ` Ira Weiny
2020-02-11 20:42       ` Dave Chinner
2020-02-12 16:10         ` Ira Weiny
2020-02-08 19:34 ` [PATCH v3 07/12] fs: Add locking for a dynamic DAX state ira.weiny
2020-02-11  8:00   ` Dave Chinner
2020-02-11 20:14     ` Ira Weiny
2020-02-11 20:59       ` Dan Williams
2020-02-11 21:49       ` Dave Chinner
2020-02-12  6:31         ` Darrick J. Wong
2020-02-08 19:34 ` [PATCH v3 08/12] fs/xfs: Clarify lockdep dependency for xfs_isilocked() ira.weiny
2020-02-08 19:34 ` [PATCH v3 09/12] fs/xfs: Add write DAX lock to xfs layer ira.weiny
2020-02-08 19:34 ` [PATCH v3 10/12] fs: Prevent DAX state change if file is mmap'ed ira.weiny
2020-02-08 19:34 ` [PATCH v3 11/12] fs/xfs: Clean up locking in dax invalidate ira.weiny
2020-02-08 19:34 ` [PATCH v3 12/12] fs/xfs: Allow toggle of effective DAX flag ira.weiny
2020-02-10 15:15 ` [PATCH v3 00/12] Enable per-file/directory DAX operations V3 Jeff Moyer
2020-02-11 20:17   ` Ira Weiny
2020-02-12 19:49     ` Jeff Moyer
2020-02-13 19:01       ` Ira Weiny
2020-02-13 19:05         ` Ira Weiny
2020-02-13 19:58           ` Darrick J. Wong
2020-02-13 23:29             ` Ira Weiny
2020-02-14  0:16               ` Dan Williams
2020-02-14 20:06                 ` Ira Weiny
2020-02-14 21:23                   ` Jeff Moyer
2020-02-14 21:58                     ` Ira Weiny
2020-02-14 22:06                       ` Jeff Moyer
2020-02-14 22:58                         ` Jeff Moyer
2020-02-14 23:03                           ` Jeff Moyer
2020-02-18  2:35                           ` Ira Weiny
2020-02-18 14:22                             ` Jeff Moyer
2020-02-18 23:54                               ` Ira Weiny
2020-02-20 16:20                                 ` Ira Weiny
2020-02-20 16:30                                   ` Darrick J. Wong
2020-02-20 16:49                                     ` Ira Weiny [this message]
2020-02-20 17:00                                       ` Darrick J. Wong

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