From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Ira Weiny <ira.weiny@intel.com>
Cc: linux-kernel@vger.kernel.org,
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>, Jan Kara <jack@suse.cz>,
linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [RFC PATCH V2 09/12] fs: Prevent mode change if file is mmap'ed
Date: Mon, 13 Jan 2020 17:30:04 -0800 [thread overview]
Message-ID: <20200114013004.GU8247@magnolia> (raw)
In-Reply-To: <20200114004610.GD29860@iweiny-DESK2.sc.intel.com>
On Mon, Jan 13, 2020 at 04:46:10PM -0800, Ira Weiny wrote:
> On Mon, Jan 13, 2020 at 02:22:12PM -0800, Darrick J. Wong wrote:
> > On Fri, Jan 10, 2020 at 11:29:39AM -0800, ira.weiny@intel.com wrote:
> > > From: Ira Weiny <ira.weiny@intel.com>
> > >
>
> [snip]
>
> > >
> > > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> > > index bc3654fe3b5d..1ab0906c6c7f 100644
> > > --- a/fs/xfs/xfs_ioctl.c
> > > +++ b/fs/xfs/xfs_ioctl.c
> > > @@ -1200,6 +1200,14 @@ xfs_ioctl_setattr_dax_invalidate(
> > > goto out_unlock;
> > > }
> > >
> > > + /*
> > > + * If there is a mapping in place we must remain in our current mode.
> > > + */
> > > + if (atomic64_read(&inode->i_mapped)) {
> >
> > Urk, should we really be messing around with the address space
> > internals?
>
> I contemplated a function call instead of checking i_mapped directly? Is that
> what you mean?
Yeah. Abstracting the details just enough that filesystems don't have
to know that i_mapped is atomic64 etc.
>
> >
> > > + error = -EBUSY;
> > > + goto out_unlock;
> > > + }
> > > +
> > > error = filemap_write_and_wait(inode->i_mapping);
> > > if (error)
> > > goto out_unlock;
> > > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > > index 631f11d6246e..6e7dc626b657 100644
> > > --- a/include/linux/fs.h
> > > +++ b/include/linux/fs.h
> > > @@ -740,6 +740,7 @@ struct inode {
> > > #endif
> > >
> > > void *i_private; /* fs or device private pointer */
> > > + atomic64_t i_mapped;
> >
> > I would have expected to find this in struct address_space since the
> > mapping count is a function of the address space, right?
>
> I suppose but the only external call (above) would be passing an inode. So to
> me it seemed better here.
But the number of memory mappings reflects the state of the address
space, not the inode. Or maybe put another way, if I were an mm
developer I would not expect to look in struct inode for mm state.
static inline bool inode_has_mappings(struct inode *inode)
{
return atomic64_read(&inode->i_mapping->mapcount) > 0;
}
OTOH if there exist other mm developers who /do/ find that storing the
mmap count in struct inode is more logical, please let me know. :)
--D
> Ira
>
> >
> > --D
> >
next prev parent reply other threads:[~2020-01-14 1:30 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-10 19:29 [RFC PATCH V2 00/12] Enable per-file/directory DAX operations V2 ira.weiny
2020-01-10 19:29 ` [RFC PATCH V2 01/12] fs/stat: Define DAX statx attribute ira.weiny
2020-01-15 11:37 ` Jan Kara
2020-01-15 17:38 ` Darrick J. Wong
2020-01-15 19:45 ` Ira Weiny
2020-01-15 20:10 ` Dan Williams
2020-01-15 22:38 ` Ira Weiny
2020-01-16 5:39 ` Darrick J. Wong
2020-01-16 6:05 ` Dan Williams
2020-01-16 6:18 ` Darrick J. Wong
2020-01-16 6:25 ` Dan Williams
2020-01-18 9:11 ` Dave Chinner
2020-01-16 17:55 ` Ira Weiny
2020-01-16 18:04 ` Darrick J. Wong
2020-01-16 18:52 ` Ira Weiny
2020-01-16 22:19 ` Darrick J. Wong
2020-01-17 11:58 ` Jan Kara
2020-01-10 19:29 ` [RFC PATCH V2 02/12] fs/xfs: Isolate the physical DAX flag from effective ira.weiny
2020-01-10 19:29 ` [RFC PATCH V2 03/12] fs/xfs: Separate functionality of xfs_inode_supports_dax() ira.weiny
2020-01-10 19:29 ` [RFC PATCH V2 04/12] fs/xfs: Clean up DAX support check ira.weiny
2020-01-10 19:29 ` [RFC PATCH V2 05/12] fs: remove unneeded IS_DAX() check ira.weiny
2020-01-16 9:38 ` Jan Kara
2020-01-16 18:47 ` Ira Weiny
2020-01-10 19:29 ` [RFC PATCH V2 06/12] fs/xfs: Check if the inode supports DAX under lock ira.weiny
2020-01-10 19:29 ` [RFC PATCH V2 07/12] fs: Add locking for a dynamic inode 'mode' ira.weiny
2020-01-13 22:12 ` Darrick J. Wong
2020-01-14 0:20 ` Ira Weiny
2020-01-14 1:03 ` Darrick J. Wong
2020-01-15 19:08 ` Ira Weiny
2020-01-16 5:40 ` Darrick J. Wong
2020-01-16 18:54 ` Ira Weiny
2020-01-10 19:29 ` [RFC PATCH V2 08/12] fs/xfs: Add lock/unlock mode to xfs ira.weiny
2020-01-13 22:19 ` Darrick J. Wong
2020-01-14 0:35 ` Ira Weiny
2020-01-15 0:57 ` Ira Weiny
2020-01-15 23:52 ` Ira Weiny
2020-01-16 9:24 ` Jan Kara
2020-01-16 19:12 ` Ira Weiny
2020-01-10 19:29 ` [RFC PATCH V2 09/12] fs: Prevent mode change if file is mmap'ed ira.weiny
2020-01-13 22:22 ` Darrick J. Wong
2020-01-14 0:46 ` Ira Weiny
2020-01-14 1:30 ` Darrick J. Wong [this message]
2020-01-14 17:53 ` Ira Weiny
2020-01-15 11:34 ` Jan Kara
2020-01-15 18:24 ` Ira Weiny
2020-01-15 10:21 ` David Laight
2020-01-15 17:53 ` Ira Weiny
2020-01-10 19:29 ` [RFC PATCH V2 10/12] fs/xfs: Fix truncate up ira.weiny
2020-01-13 22:27 ` Darrick J. Wong
2020-01-14 0:40 ` Ira Weiny
2020-01-14 1:14 ` Darrick J. Wong
2020-01-14 19:00 ` Ira Weiny
2020-01-14 19:39 ` Ira Weiny
2020-01-10 19:29 ` [RFC PATCH V2 11/12] fs/xfs: Clean up locking in dax invalidate ira.weiny
2020-01-10 19:29 ` [RFC PATCH V2 12/12] fs/xfs: Allow toggle of effective DAX flag ira.weiny
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