[Cluster-devel] [GFS2 PATCH] [TRY 2] GFS2: Instruct DLM to avoid queue convert slowdown

[Steven Whitehouse <swhiteho@redhat.com>]

Hi,

On Tue, 2012-04-10 at 14:13 -0400, Bob Peterson wrote:
> Hi,
> 
> Here is my revised patch based on Steve's suggestion to base the
> flag on the recent GLF_BLOCKING flag.
> 
> We still need to keep this on hold until the prerequisite dlm patch
> is properly upstream.
> 
> Regards,
> 
> Bob Peterson
> Red Hat File Systems
> 
> Signed-off-by: Bob Peterson <rpeterso@redhat.com> 
> ---
> Author: Bob Peterson <rpeterso@redhat.com>
> Date:   Tue Apr 10 14:08:11 2012 -0500
> 
>     GFS2: Instruct DLM to avoid queue convert slowdowns
>     
>     This patch instructs DLM to prevent an "in place" conversion, where the
>     lock just stays on the granted queue, and instead forces the conversion to
>     the back of the convert queue. This is done on upward conversions only.
>     
>     This is useful in cases where, for example, a lock is frequently needed in
>     PR on one node, but another node needs it temporarily in EX to update it.
>     This may happen, for example, when the rindex is being updated by gfs2_grow.
>     The gfs2_grow needs to have the lock in EX, but the other nodes need to
>     re-read it to retrieve the updates. The glock is already granted in PR on
>     the non-growing nodes, so this prevents them from continually re-granting
>     the lock in PR, and forces the EX from gfs2_grow to go through.
> 
> diff --git a/fs/gfs2/lock_dlm.c b/fs/gfs2/lock_dlm.c
> index f8411bd..ed9c5ca 100644
> --- a/fs/gfs2/lock_dlm.c
> +++ b/fs/gfs2/lock_dlm.c
> @@ -200,11 +200,15 @@ static int make_mode(const unsigned int lmstate)
>  	return -1;
>  }
>  
> -static u32 make_flags(const u32 lkid, const unsigned int gfs_flags,
> +static u32 make_flags(struct gfs2_glock *gl, const unsigned int gfs_flags,
>  		      const int req)
>  {
>  	u32 lkf = DLM_LKF_VALBLK;
> +	u32 lkid = gl->gl_lksb.sb_lkid;
> +	int is_upconvert = 0;
>  
> +	if (test_bit(GLF_BLOCKING, &gl->gl_flags))
> +		is_upconvert = 1;
Rather than create this is_upconvert variable here...

>  	if (gfs_flags & LM_FLAG_TRY)
>  		lkf |= DLM_LKF_NOQUEUE;
>  
> @@ -227,8 +231,11 @@ static u32 make_flags(const u32 lkid, const unsigned int gfs_flags,
>  			BUG();
>  	}
>  
> -	if (lkid != 0) 
> +	if (lkid != 0) {
>  		lkf |= DLM_LKF_CONVERT;
> +		if (is_upconvert)
why not just test the flag bit here?

Otherwise looks good,

Steve.

> +			lkf |= DLM_LKF_QUECVT;
> +	}
>  
>  	return lkf;
>  }
> @@ -250,7 +257,7 @@ static int gdlm_lock(struct gfs2_glock *gl, unsigned int req_state,
>  	char strname[GDLM_STRNAME_BYTES] = "";
>  
>  	req = make_mode(req_state);
> -	lkf = make_flags(gl->gl_lksb.sb_lkid, flags, req);
> +	lkf = make_flags(gl, flags, req);
>  	gfs2_glstats_inc(gl, GFS2_LKS_DCOUNT);
>  	gfs2_sbstats_inc(gl, GFS2_LKS_DCOUNT);
>  	if (gl->gl_lksb.sb_lkid) {
>