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Re: [RFC PATCH 2/2] xfs_export_operations.commit_metadata

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [RFC PATCH 2/2] xfs_export_operations.commit_metadata
From: bpm@xxxxxxx
Date: Wed, 10 Feb 2010 14:15:27 -0600
Cc: linux-nfs@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx
In-reply-to: <20100210090750.GB21875@xxxxxxxxxxxxx>
References: <20100210003220.6021.74943.stgit@case> <20100210003337.6021.10942.stgit@case> <20100210090750.GB21875@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.18 (2008-05-17)
Howdy,

On Wed, Feb 10, 2010 at 04:07:50AM -0500, Christoph Hellwig wrote:
> On Tue, Feb 09, 2010 at 06:33:37PM -0600, Ben Myers wrote:
> > hopefully
> > the XFS gurus can continue to provide guidance.
> 
> Ccing the xfs list would help with that :) 

I'll cross-post the next rev.  ;)

> > +           if (xfs_ipincount(c_xip)) {
> > +                   /*
> > +                    * AFAICS the child is always modified after the parent
> > +                    * in nfsd so should always have a larger lsn.
> > +                    */
> > +                   if (c_xip->i_itemp->ili_last_lsn > force_lsn) {
> > +                           force_lsn = c_xip->i_itemp->ili_last_lsn;
> > +                   } else {
> > +                           force_lsn = 0; /* whole thing */
> > +                   }
> 
> I wouldn't rely on that and always take the larger one.

I am concerned that ili_last_lsn will roll over at some point.  I
haven't figured out how to detect that yet.
 
> Now with the simplification of always having a non-zero first argument
> suggested in the previous mail this might be simplified down to:
> 
> STATIC int
> xfs_fs_nfs_commit_metadata(
>       struct dentry           *parent,
>       struct dentry           *child)
> {
>       struct xfs_inode        *dp = XFS_I(parent->d_inode);
>       struct xfs_inode        *ip = NULL;
>       struct xfs_mount        *mp = dp->i_mount;
>       xfs_lsn_t               force_lsn = 0;
>       int                     error = 0;
> 
>       if (child) {
>               ip = XFS_I(child->d_inode);
>               xfs_lock_two_inodes(dp, ip, XFS_ILOCK_SHARED);
>       } else {
>               xfs_ilock(dp, XFS_ILOCK_SHARED);
>       }
> 
>       if (xfs_ipincount(dp))
>               force_lsn = dp->i_itemp->ili_last_lsn;
>       if (ip && xfs_ipincount(ip))
>               force_lsn = max(force_lsn, ip->i_itemp->ili_last_lsn);
> 
+       if (force_lsn)
>               error = _xfs_log_force_lsn(mp, force_lsn, NULL);
> 
>       if (ip)
>               xfs_iunlock(ip, XFS_ILOCK_SHARED);
>       xfs_iunlock(dp, XFS_ILOCK_SHARED);
> 
>       return error;
> }

That's nice!

> Note that _xfs_log_force_lsn is new in the XFS tree, mainline still
> has _xfs_log_force with an lsn argument.

I've been working with Bruce's tree.  Not sure how best to handle that.

Thanks,
        Ben

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