From: Ira Weiny <ira.weiny@intel.com>
To: Jan Kara <jack@suse.cz>
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>,
linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [RFC PATCH V2 08/12] fs/xfs: Add lock/unlock mode to xfs
Date: Thu, 16 Jan 2020 11:12:10 -0800 [thread overview]
Message-ID: <20200116191210.GG24522@iweiny-DESK2.sc.intel.com> (raw)
In-Reply-To: <20200116092446.GA8446@quack2.suse.cz>
On Thu, Jan 16, 2020 at 10:24:46AM +0100, Jan Kara wrote:
> On Fri 10-01-20 11:29:38, ira.weiny@intel.com wrote:
> > From: Ira Weiny <ira.weiny@intel.com>
> >
> > XFS requires regular files to be locked while changing to/from DAX mode.
> >
> > Define a new DAX lock type and implement the [un]lock_mode() inode
> > operation callbacks.
> >
> > We define a new XFS_DAX_* lock type to carry the lock through the
> > transaction because we don't want to use IOLOCK as that would cause
> > performance issues with locking of the inode itself.
> >
> > Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> ...
> > diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
> > index 492e53992fa9..693ca66bd89b 100644
> > --- a/fs/xfs/xfs_inode.h
> > +++ b/fs/xfs/xfs_inode.h
> > @@ -67,6 +67,9 @@ typedef struct xfs_inode {
> > spinlock_t i_ioend_lock;
> > struct work_struct i_ioend_work;
> > struct list_head i_ioend_list;
> > +
> > + /* protect changing the mode to/from DAX */
> > + struct percpu_rw_semaphore i_dax_sem;
> > } xfs_inode_t;
>
> This adds overhead of ~32k per inode for typical distro kernel.
Wow!
> That's not
> going to fly.
Probably not...
> That's why ext4 has similar kind of lock in the superblock
> shared by all inodes. For read side it does not matter because that's
> per-cpu and shared lock. For write side we don't care as changing inode
> access mode should be rare.
Sounds reasonable to me. I'll convert it.
Thanks for pointing this out, that would have been bad indeed.
Ira
next prev parent reply other threads:[~2020-01-16 19:12 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 [this message]
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
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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