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>

7 files changed, 43 insertions, 21 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 0e73aa0..cb9d050 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -883,6 +883,11 @@ static int shrink_dcache_memory(int nr, gfp_t gfp_mask)
 	return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
 }
 
+static struct shrinker dcache_shrinker = {
+	.shrink = shrink_dcache_memory,
+	.seeks = DEFAULT_SEEKS,
+};
+
 /**
  * d_alloc	-	allocate a dcache entry
  * @parent: parent of entry to allocate
@@ -2115,7 +2120,7 @@ static void __init dcache_init(unsigned long mempages)
 	dentry_cache = KMEM_CACHE(dentry,
 		SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
 	
-	set_shrinker(DEFAULT_SEEKS, shrink_dcache_memory);
+	register_shrinker(&dcache_shrinker);
 
 	/* Hash may have been set up in dcache_init_early */
 	if (!hashdist)
diff --git a/fs/dquot.c b/fs/dquot.c
index 8819d28..7e27315 100644
--- a/fs/dquot.c
+++ b/fs/dquot.c
@@ -538,6 +538,11 @@ static int shrink_dqcache_memory(int nr, gfp_t gfp_mask)
 	return (dqstats.free_dquots / 100) * sysctl_vfs_cache_pressure;
 }
 
+static struct shrinker dqcache_shrinker = {
+	.shrink = shrink_dqcache_memory,
+	.seeks = DEFAULT_SEEKS,
+};
+
 /*
  * Put reference to dquot
  * NOTE: If you change this function please check whether dqput_blocks() works right...
@@ -1870,7 +1875,7 @@ static int __init dquot_init(void)
 	printk("Dquot-cache hash table entries: %ld (order %ld, %ld bytes)\n",
 			nr_hash, order, (PAGE_SIZE << order));
 
-	set_shrinker(DEFAULT_SEEKS, shrink_dqcache_memory);
+	register_shrinker(&dqcache_shrinker);
 
 	return 0;
 }
diff --git a/fs/inode.c b/fs/inode.c
index 47b87b0..320e088 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -462,6 +462,11 @@ static int shrink_icache_memory(int nr, gfp_t gfp_mask)
 	return (inodes_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
 }
 
+static struct shrinker icache_shrinker = {
+	.shrink = shrink_icache_memory,
+	.seeks = DEFAULT_SEEKS,
+};
+
 static void __wait_on_freeing_inode(struct inode *inode);
 /*
  * Called with the inode lock held.
@@ -1385,7 +1390,7 @@ void __init inode_init(unsigned long mempages)
 					 SLAB_MEM_SPREAD),
 					 init_once,
 					 NULL);
-	set_shrinker(DEFAULT_SEEKS, shrink_icache_memory);
+	register_shrinker(&icache_shrinker);
 
 	/* Hash may have been set up in inode_init_early */
 	if (!hashdist)
diff --git a/fs/mbcache.c b/fs/mbcache.c
index deeb9dc..fbb1d02 100644
--- a/fs/mbcache.c
+++ b/fs/mbcache.c
@@ -100,7 +100,6 @@ struct mb_cache {
 static LIST_HEAD(mb_cache_list);
 static LIST_HEAD(mb_cache_lru_list);
 static DEFINE_SPINLOCK(mb_cache_spinlock);
-static struct shrinker *mb_shrinker;
 
 static inline int
 mb_cache_indexes(struct mb_cache *cache)
@@ -118,6 +117,10 @@ mb_cache_indexes(struct mb_cache *cache)
 
 static int mb_cache_shrink_fn(int nr_to_scan, gfp_t gfp_mask);
 
+static struct shrinker mb_cache_shrinker = {
+	.shrink = mb_cache_shrink_fn,
+	.seeks = DEFAULT_SEEKS,
+};
 
 static inline int
 __mb_cache_entry_is_hashed(struct mb_cache_entry *ce)
@@ -662,13 +665,13 @@ mb_cache_entry_find_next(struct mb_cache_entry *prev, int index,
 
 static int __init init_mbcache(void)
 {
-	mb_shrinker = set_shrinker(DEFAULT_SEEKS, mb_cache_shrink_fn);
+	register_shrinker(&mb_cache_shrinker);
 	return 0;
 }
 
 static void __exit exit_mbcache(void)
 {
-	remove_shrinker(mb_shrinker);
+	unregister_shrinker(&mb_cache_shrinker);
 }
 
 module_init(init_mbcache)
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index a2b1af8..adffe16 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -300,7 +300,10 @@ static const struct super_operations nfs4_sops = {
 };
 #endif
 
-static struct shrinker *acl_shrinker;
+static struct shrinker acl_shrinker = {
+	.shrink		= nfs_access_cache_shrinker,
+	.seeks		= DEFAULT_SEEKS,
+};
 
 /*
  * Register the NFS filesystems
@@ -321,7 +324,7 @@ int __init register_nfs_fs(void)
 	if (ret < 0)
 		goto error_2;
 #endif
-	acl_shrinker = set_shrinker(DEFAULT_SEEKS, nfs_access_cache_shrinker);
+	register_shrinker(&acl_shrinker);
 	return 0;
 
 #ifdef CONFIG_NFS_V4
@@ -339,8 +342,7 @@ error_0:
  */
 void __exit unregister_nfs_fs(void)
 {
-	if (acl_shrinker != NULL)
-		remove_shrinker(acl_shrinker);
+	unregister_shrinker(&acl_shrinker);
 #ifdef CONFIG_NFS_V4
 	unregister_filesystem(&nfs4_fs_type);
 	nfs_unregister_sysctl();
diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c
index 2df6362..b0f0e58 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 7def4c6..2d274b2 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]));