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>

1 files changed, 11 insertions, 31 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 1d9971d8924b..2225b7c9df85 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -70,17 +70,6 @@ struct scan_control {
         int order;
 };
 
-/*
- * The list of shrinker callbacks used by to apply pressure to
- * ageable caches.
- */
-struct shrinker {
-        shrinker_t              shrinker;
-        struct list_head        list;
-        int                     seeks;  /* seeks to recreate an obj */
-        long                    nr;     /* objs pending delete */
-};
-
 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
 
 #ifdef ARCH_HAS_PREFETCH
@@ -123,34 +112,25 @@ static DECLARE_RWSEM(shrinker_rwsem);
 /*
  * Add a shrinker callback to be called from the vm
  */
-struct shrinker *set_shrinker(int seeks, shrinker_t theshrinker)
+void register_shrinker(struct shrinker *shrinker)
 {
-        struct shrinker *shrinker;
-
-        shrinker = kmalloc(sizeof(*shrinker), GFP_KERNEL);
-        if (shrinker) {
-                shrinker->shrinker = theshrinker;
-                shrinker->seeks = seeks;
-                shrinker->nr = 0;
-                down_write(&shrinker_rwsem);
-                list_add_tail(&shrinker->list, &shrinker_list);
-                up_write(&shrinker_rwsem);
-        }
-        return shrinker;
+        shrinker->nr = 0;
+        down_write(&shrinker_rwsem);
+        list_add_tail(&shrinker->list, &shrinker_list);
+        up_write(&shrinker_rwsem);
 }
-EXPORT_SYMBOL(set_shrinker);
+EXPORT_SYMBOL(register_shrinker);
 
 /*
  * Remove one
  */
-void remove_shrinker(struct shrinker *shrinker)
+void unregister_shrinker(struct shrinker *shrinker)
 {
         down_write(&shrinker_rwsem);
         list_del(&shrinker->list);
         up_write(&shrinker_rwsem);
-        kfree(shrinker);
 }
-EXPORT_SYMBOL(remove_shrinker);
+EXPORT_SYMBOL(unregister_shrinker);
 
 #define SHRINK_BATCH 128
 /*
@@ -187,7 +167,7 @@ unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
         list_for_each_entry(shrinker, &shrinker_list, list) {
                 unsigned long long delta;
                 unsigned long total_scan;
-                unsigned long max_pass = (*shrinker->shrinker)(0, gfp_mask);
+                unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask);
 
                 delta = (4 * scanned) / shrinker->seeks;
                 delta *= max_pass;
@@ -215,8 +195,8 @@ unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
                         int shrink_ret;
                         int nr_before;
 
-                        nr_before = (*shrinker->shrinker)(0, gfp_mask);
-                        shrink_ret = (*shrinker->shrinker)(this_scan, gfp_mask);
+                        nr_before = (*shrinker->shrink)(0, gfp_mask);
+                        shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
                         if (shrink_ret == -1)
                                 break;
                         if (shrink_ret < nr_before)