Re: [PATCH v7 18/34] fs: convert fs shrinkers to new scan/count API

[Steven Whitehouse <swhiteho@redhat.com>]

Hi,

On Mon, 2013-05-20 at 00:07 +0400, Glauber Costa wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> Convert the filesystem shrinkers to use the new API, and standardise
> some of the behaviours of the shrinkers at the same time. For
> example, nr_to_scan means the number of objects to scan, not the
> number of objects to free.
> 
> I refactored the CIFS idmap shrinker a little - it really needs to
> be broken up into a shrinker per tree and keep an item count with
> the tree root so that we don't need to walk the tree every time the
> shrinker needs to count the number of objects in the tree (i.e.
> all the time under memory pressure).
> 
> [ glommer: fixes for ext4, ubifs, nfs, cifs and glock. Fixes are
>   needed mainly due to new code merged in the tree ]
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> Signed-off-by: Glauber Costa <glommer@openvz.org>
> Acked-by: Mel Gorman <mgorman@suse.de>
> Acked-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
> Acked-by: Jan Kara <jack@suse.cz>
> CC: Steven Whitehouse <swhiteho@redhat.com>
> CC: Adrian Hunter <adrian.hunter@intel.com>
> ---
>  fs/ext4/extents_status.c | 30 ++++++++++++++++------------
>  fs/gfs2/glock.c          | 28 +++++++++++++++-----------
>  fs/gfs2/main.c           |  3 ++-
>  fs/gfs2/quota.c          | 12 +++++++-----
>  fs/gfs2/quota.h          |  4 +++-
>  fs/mbcache.c             | 51 ++++++++++++++++++++++++++++--------------------
>  fs/nfs/dir.c             | 18 ++++++++++++++---
>  fs/nfs/internal.h        |  4 +++-
>  fs/nfs/super.c           |  3 ++-
>  fs/nfsd/nfscache.c       | 31 ++++++++++++++++++++---------
>  fs/quota/dquot.c         | 34 +++++++++++++++-----------------
>  fs/ubifs/shrinker.c      | 20 +++++++++++--------
>  fs/ubifs/super.c         |  3 ++-
>  fs/ubifs/ubifs.h         |  3 ++-
>  14 files changed, 151 insertions(+), 93 deletions(-)
[snip]
>  		return 0;
> diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
> index 3bd2748..4ddbccb 100644
> --- a/fs/gfs2/glock.c
> +++ b/fs/gfs2/glock.c
> @@ -1428,21 +1428,22 @@ __acquires(&lru_lock)
>   * gfs2_dispose_glock_lru() above.
>   */
>  
> -static void gfs2_scan_glock_lru(int nr)
> +static long gfs2_scan_glock_lru(int nr)
>  {
>  	struct gfs2_glock *gl;
>  	LIST_HEAD(skipped);
>  	LIST_HEAD(dispose);
> +	long freed = 0;
>  
>  	spin_lock(&lru_lock);
> -	while(nr && !list_empty(&lru_list)) {
> +	while ((nr-- >= 0) && !list_empty(&lru_list)) {
>  		gl = list_entry(lru_list.next, struct gfs2_glock, gl_lru);
>  
>  		/* Test for being demotable */
>  		if (!test_and_set_bit(GLF_LOCK, &gl->gl_flags)) {
>  			list_move(&gl->gl_lru, &dispose);
>  			atomic_dec(&lru_count);
> -			nr--;
> +			freed++;
>  			continue;
>  		}
>  

This seems to change behaviour so that nr is no longer the number of
items to be demoted, but instead the max number of items to scan in
order to look for items to be demoted. Does that mean that nr has
changed its meaning now?

Steve.



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