mm: clean up and kernelify shrinker registration

I can never remember what the function to register to receive VM pressure
is called.  I have to trace down from __alloc_pages() to find it.

It's called "set_shrinker()", and it needs Your Help.

1) Don't hide struct shrinker.  It contains no magic.
2) Don't allocate "struct shrinker".  It's not helpful.
3) Call them "register_shrinker" and "unregister_shrinker".
4) Call the function "shrink" not "shrinker".
5) Reduce the 17 lines of waffly comments to 13, but document it properly.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: David Chinner <dgc@sgi.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 13 insertions, 11 deletions

diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c
index 2df63622354e..b0f0e58866de 100644
--- a/fs/xfs/linux-2.6/xfs_buf.c
+++ b/fs/xfs/linux-2.6/xfs_buf.c
@@ -35,10 +35,13 @@
 #include <linux/freezer.h>
 
 static kmem_zone_t *xfs_buf_zone;
-static struct shrinker *xfs_buf_shake;
 STATIC int xfsbufd(void *);
 STATIC int xfsbufd_wakeup(int, gfp_t);
 STATIC void xfs_buf_delwri_queue(xfs_buf_t *, int);
+static struct shrinker xfs_buf_shake = {
+        .shrink = xfsbufd_wakeup,
+        .seeks = DEFAULT_SEEKS,
+};
 
 static struct workqueue_struct *xfslogd_workqueue;
 struct workqueue_struct *xfsdatad_workqueue;
@@ -1832,14 +1835,9 @@ xfs_buf_init(void)
         if (!xfsdatad_workqueue)
                 goto out_destroy_xfslogd_workqueue;
 
-        xfs_buf_shake = set_shrinker(DEFAULT_SEEKS, xfsbufd_wakeup);
-        if (!xfs_buf_shake)
-                goto out_destroy_xfsdatad_workqueue;
-
+        register_shrinker(&xfs_buf_shake);
         return 0;
 
- out_destroy_xfsdatad_workqueue:
-        destroy_workqueue(xfsdatad_workqueue);
  out_destroy_xfslogd_workqueue:
         destroy_workqueue(xfslogd_workqueue);
  out_free_buf_zone:
@@ -1854,7 +1852,7 @@ xfs_buf_init(void)
 void
 xfs_buf_terminate(void)
 {
-        remove_shrinker(xfs_buf_shake);
+        unregister_shrinker(&xfs_buf_shake);
         destroy_workqueue(xfsdatad_workqueue);
         destroy_workqueue(xfslogd_workqueue);
         kmem_zone_destroy(xfs_buf_zone);
diff --git a/fs/xfs/quota/xfs_qm.c b/fs/xfs/quota/xfs_qm.c
index 7def4c699343..2d274b23ade5 100644
--- a/fs/xfs/quota/xfs_qm.c
+++ b/fs/xfs/quota/xfs_qm.c
@@ -62,7 +62,6 @@ uint		ndquot;
 
 kmem_zone_t     *qm_dqzone;
 kmem_zone_t     *qm_dqtrxzone;
-static struct shrinker *xfs_qm_shaker;
 
 static cred_t   xfs_zerocr;
 
@@ -78,6 +77,11 @@ STATIC int	xfs_qm_init_quotainos(xfs_mount_t *);
 STATIC int      xfs_qm_init_quotainfo(xfs_mount_t *);
 STATIC int      xfs_qm_shake(int, gfp_t);
 
+static struct shrinker xfs_qm_shaker = {
+        .shrink = xfs_qm_shake,
+        .seeks = DEFAULT_SEEKS,
+};
+
 #ifdef DEBUG
 extern mutex_t  qcheck_lock;
 #endif
@@ -149,7 +153,7 @@ xfs_Gqm_init(void)
         } else
                 xqm->qm_dqzone = qm_dqzone;
 
-        xfs_qm_shaker = set_shrinker(DEFAULT_SEEKS, xfs_qm_shake);
+        register_shrinker(&xfs_qm_shaker);
 
         /*
          * The t_dqinfo portion of transactions.
@@ -181,7 +185,7 @@ xfs_qm_destroy(
 
         ASSERT(xqm != NULL);
         ASSERT(xqm->qm_nrefs == 0);
-        remove_shrinker(xfs_qm_shaker);
+        unregister_shrinker(&xfs_qm_shaker);
         hsize = xqm->qm_dqhashmask + 1;
         for (i = 0; i < hsize; i++) {
                 xfs_qm_list_destroy(&(xqm->qm_usr_dqhtable[i]));