Re: [PATCH 1/4] xfs: xfs_iflock is no longer a completion

From: Dave Chinner <david@fromorbit.com>
To: Brian Foster <bfoster@redhat.com>
Cc: linux-xfs@vger.kernel.org
Subject: Re: [PATCH 1/4] xfs: xfs_iflock is no longer a completion
Date: Wed, 1 Jul 2020 15:48:50 +1000	[thread overview]
Message-ID: <20200701054850.GR2005@dread.disaster.area> (raw)
In-Reply-To: <20200624153652.GD9914@bfoster>

On Wed, Jun 24, 2020 at 11:36:52AM -0400, Brian Foster wrote:
> On Tue, Jun 23, 2020 at 07:50:12PM +1000, Dave Chinner wrote:
> > From: Dave Chinner <dchinner@redhat.com>
> > 
> > With the recent rework of the inode cluster flushing, we no longer
> > ever wait on the the inode flush "lock". It was never a lock in the
> > first place, just a completion to allow callers to wait for inode IO
> > to complete. We now never wait for flush completion as all inode
> > flushing is non-blocking. Hence we can get rid of all the iflock
> > infrastructure and instead just set and check a state flag.
> > 
> > Rename the XFS_IFLOCK flag to XFS_IFLUSHING, convert all the
> > xfs_iflock_nowait() test-and-set operations on that flag, and
> > replace all the xfs_ifunlock() calls to clear operations.
> > 
> > Signed-off-by: Dave Chinner <dchinner@redhat.com>
> > ---
> 
> I'd call it IFLUSHED vs. IFLUSHING, but I'm not going to harp on that.
> Just a few nits, otherwise looks like a nice cleanup.

I thought about "flushed" but that implies something that has
alerady happened in the past (e.g. XFS_ITRUNCATED) rather than
something that is currently happening. i.e. we are wanting to know
if a flush is in progress right now, not whether a flush has been
done in the past...

> >  fs/xfs/xfs_icache.c     | 19 ++++++------
> >  fs/xfs/xfs_inode.c      | 67 +++++++++++++++--------------------------
> >  fs/xfs/xfs_inode.h      | 33 +-------------------
> >  fs/xfs/xfs_inode_item.c |  6 ++--
> >  fs/xfs/xfs_inode_item.h |  4 +--
> >  5 files changed, 39 insertions(+), 90 deletions(-)
> > 
> > diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
> > index a973f180c6cd..0d73559f2d58 100644
> > --- a/fs/xfs/xfs_icache.c
> > +++ b/fs/xfs/xfs_icache.c
> ...
> > @@ -1045,23 +1044,23 @@ xfs_reclaim_inode(
> >  
> >  	if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL))
> >  		goto out;
> > -	if (!xfs_iflock_nowait(ip))
> > +	if (xfs_iflags_test_and_set(ip, XFS_IFLUSHING))
> >  		goto out_iunlock;
> >  
> >  	if (XFS_FORCED_SHUTDOWN(ip->i_mount)) {
> >  		xfs_iunpin_wait(ip);
> >  		/* xfs_iflush_abort() drops the flush lock */
> 
> The flush what? ;P
> 
> >  		xfs_iflush_abort(ip);
> > +		ASSERT(!xfs_iflags_test(ip, XFS_IFLUSHING));
> 
> Seems a bit superfluous right after the abort.

Yup, I'll that clean up and the comments the search and replace I
did missed.

Thanks!

-Dave.
-- 
Dave Chinner
david@fromorbit.com