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Re: [PATCH 1/5] xfs: introduce inode cluster buffer trylocks for xfs_ifl

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH 1/5] xfs: introduce inode cluster buffer trylocks for xfs_iflush
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Fri, 4 Mar 2011 09:04:44 +1100
Cc: xfs@xxxxxxxxxxx, chris.mason@xxxxxxxxxx
In-reply-to: <20110303155535.GA12670@xxxxxxxxxxxxx>
References: <1298412969-14389-1-git-send-email-david@xxxxxxxxxxxxx> <1298412969-14389-2-git-send-email-david@xxxxxxxxxxxxx> <20110303155535.GA12670@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.20 (2009-06-14)
On Thu, Mar 03, 2011 at 10:55:35AM -0500, Christoph Hellwig wrote:
> > +    * pass through will see the stale flag set on the inode.
> > +    */
> > +   error = xfs_iflush(ip, SYNC_TRYLOCK | sync_mode);
> >     if (sync_mode & SYNC_WAIT) {
> > +           if (error == EAGAIN) {
> > +                   xfs_iunlock(ip, XFS_ILOCK_EXCL);
> > +                   /* backoff longer than in xfs_ifree_cluster */
> > +                   delay(2);
> 
> Do we really need the delay here?  It seems like we'd rather want to
> keep going with scanning the next inode cluster and return here from
> xfs_reclaim_inodes.

I did that because SYNC_WAIT semantics mean "block until the inode
is reclaimed". This is the slow, reliable reclaim path that doesn't
return until the inode is reclaimed, so we have to have a backoff
here to allow xfs_ifree_cluster() to complete it's backoff and gain
the locks successfully thereby allowing the inode to be reclaimed
successfully.

> > diff --git a/fs/xfs/linux-2.6/xfs_sync.h b/fs/xfs/linux-2.6/xfs_sync.h
> > index 32ba662..0ae48ff 100644
> > --- a/fs/xfs/linux-2.6/xfs_sync.h
> > +++ b/fs/xfs/linux-2.6/xfs_sync.h
> > @@ -34,6 +34,7 @@ typedef struct xfs_sync_work {
> >  
> >  int xfs_syncd_init(struct xfs_mount *mp);
> >  void xfs_syncd_stop(struct xfs_mount *mp);
> > +void xfs_syncd_queue_sync(struct xfs_mount *mp, int flags);
> 
> This hunk belongs into a different patch.

Oops. Will fix.

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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