[Cluster-devel] [GFS2] Fix bz 231380, unlock page before dequeing glocks in gfs2_commit_write

[Steven Whitehouse <swhiteho@redhat.com>]

Hi,

Now applied to the -nmw git tree. I think this is the right fix, at
least for now,

Steve.

On Mon, 2007-03-12 at 16:55 -0500, Josef Whiter wrote:
> Hello,
> 
> I'm not entirely sure if this is the best fix for this problem, so I'm open for
> suggetions.  If we are writing a file, and in the middle of writing the file
> another node attempts to get a shared lock on that file (by doing a du for
> example) the process doing the writing will hang waiting on lock_page.  The
> reason for this is because when we have waiters on a exclusive glock, we will go
> through and flush out all dirty pages associated with that inode and release the
> lock.  The problem is that when we flush the dirty pages, we could hit a page
> that we have locked durring the generic_file_buffered_write part of this
> operation.  This patch unlocks the page before we go to dequeue the lock and
> locks it immediatly afterwards, since generic_file_buffered_write needs the page
> locked when the commit_write is completed.  This patch resolves the problem,
> however if somebody sees a better way to do this please don't hesistate to yell.
> Thank you,
> 
> Josef
> 
> 
> Signed-off-by: Josef Whiter <jwhiter@redhat.com>
> 
> 
> --- gfs2-2.6-nmw/fs/gfs2/ops_address.c.josef	2007-03-08 15:04:10.000000000 -0500
> +++ gfs2-2.6-nmw/fs/gfs2/ops_address.c	2007-03-12 17:23:24.000000000 -0400
> @@ -507,7 +507,9 @@
>  		gfs2_quota_unlock(ip);
>  		gfs2_alloc_put(ip);
>  	}
> +	unlock_page(page);
>  	gfs2_glock_dq_m(1, &ip->i_gh);
> +	lock_page(page);
>  	gfs2_holder_uninit(&ip->i_gh);
>  	return 0;
>  
> @@ -520,7 +522,9 @@
>  		gfs2_quota_unlock(ip);
>  		gfs2_alloc_put(ip);
>  	}
> +	unlock_page(page);
>  	gfs2_glock_dq_m(1, &ip->i_gh);
> +	lock_page(page);
>  	gfs2_holder_uninit(&ip->i_gh);
>  fail_nounlock:
>  	ClearPageUptodate(page);
>