Use ilog2() in fs/namespace.c

We can use ilog2() in fs/namespace.c to compute hash_bits and hash_mask at
compile time, not runtime.

[akpm@linux-foundation.org: clean it all up]
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/namespace.c b/fs/namespace.c
index 61bf376..e9c10cd 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -25,18 +25,21 @@
 #include <linux/security.h>
 #include <linux/mount.h>
 #include <linux/ramfs.h>
+#include <linux/log2.h>
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
 #include "pnode.h"
 #include "internal.h"
 
+#define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head))
+#define HASH_SIZE (1UL << HASH_SHIFT)
+
 /* spinlock for vfsmount related operations, inplace of dcache_lock */
 __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock);
 
 static int event;
 
 static struct list_head *mount_hashtable __read_mostly;
-static int hash_mask __read_mostly, hash_bits __read_mostly;
 static struct kmem_cache *mnt_cache __read_mostly;
 static struct rw_semaphore namespace_sem;
 
@@ -48,8 +51,8 @@ static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
 {
        unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
        tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
-       tmp = tmp + (tmp >> hash_bits);
-       return tmp & hash_mask;
+       tmp = tmp + (tmp >> HASH_SHIFT);
+       return tmp & (HASH_SIZE - 1);
 }
 
 struct vfsmount *alloc_vfsmnt(const char *name)
@@ -1813,9 +1816,7 @@ static void __init init_mount_tree(void)
 
 void __init mnt_init(void)
 {
-       struct list_head *d;
-       unsigned int nr_hash;
-       int i;
+       unsigned u;
        int err;
 
        init_rwsem(&namespace_sem);
@@ -1828,35 +1829,11 @@ void __init mnt_init(void)
        if (!mount_hashtable)
                panic("Failed to allocate mount hash table\n");
 
-       /*
-        * Find the power-of-two list-heads that can fit into the allocation..
-        * We don't guarantee that "sizeof(struct list_head)" is necessarily
-        * a power-of-two.
-        */
-       nr_hash = PAGE_SIZE / sizeof(struct list_head);
-       hash_bits = 0;
-       do {
-               hash_bits++;
-       } while ((nr_hash >> hash_bits) != 0);
-       hash_bits--;
+       printk("Mount-cache hash table entries: %lu\n", HASH_SIZE);
+
+       for (u = 0; u < HASH_SIZE; u++)
+               INIT_LIST_HEAD(&mount_hashtable[u]);
 
-       /*
-        * Re-calculate the actual number of entries and the mask
-        * from the number of bits we can fit.
-        */
-       nr_hash = 1UL << hash_bits;
-       hash_mask = nr_hash - 1;
-
-       printk("Mount-cache hash table entries: %d\n", nr_hash);
-
-       /* And initialize the newly allocated array */
-       d = mount_hashtable;
-       i = nr_hash;
-       do {
-               INIT_LIST_HEAD(d);
-               d++;
-               i--;
-       } while (i);
        err = sysfs_init();
        if (err)
                printk(KERN_WARNING "%s: sysfs_init error: %d\n",