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Use ilog2() in fs/namespace.c

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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>
This commit is contained in:
Eric Dumazet 2008-02-06 01:37:57 -08:00 committed by Linus Torvalds
parent b41ecbebd4
commit 13f14b4d8b
1 changed files with 10 additions and 33 deletions
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43
fs/namespace.c
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@ -25,18 +25,21 @@
#include <linux/security.h> #include <linux/security.h>
#include <linux/mount.h> #include <linux/mount.h>
#include <linux/ramfs.h> #include <linux/ramfs.h>
#include <linux/log2.h>
#include <asm/uaccess.h> #include <asm/uaccess.h>
#include <asm/unistd.h> #include <asm/unistd.h>
#include "pnode.h" #include "pnode.h"
#include "internal.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 */ /* spinlock for vfsmount related operations, inplace of dcache_lock */
__cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock); __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock);
static int event; static int event;
static struct list_head *mount_hashtable __read_mostly; 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 kmem_cache *mnt_cache __read_mostly;
static struct rw_semaphore namespace_sem; 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); unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
tmp += ((unsigned long)dentry / L1_CACHE_BYTES); tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
tmp = tmp + (tmp >> hash_bits); tmp = tmp + (tmp >> HASH_SHIFT);
return tmp & hash_mask; return tmp & (HASH_SIZE - 1);
} }
struct vfsmount *alloc_vfsmnt(const char *name) struct vfsmount *alloc_vfsmnt(const char *name)
@ -1813,9 +1816,7 @@ static void __init init_mount_tree(void)
void __init mnt_init(void) void __init mnt_init(void)
{ {
struct list_head *d; unsigned u;
unsigned int nr_hash;
int i;
int err; int err;
init_rwsem(&namespace_sem); init_rwsem(&namespace_sem);
@ -1828,35 +1829,11 @@ void __init mnt_init(void)
if (!mount_hashtable) if (!mount_hashtable)
panic("Failed to allocate mount hash table\n"); panic("Failed to allocate mount hash table\n");
/* printk("Mount-cache hash table entries: %lu\n", HASH_SIZE);
* 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--;
/* for (u = 0; u < HASH_SIZE; u++)
* Re-calculate the actual number of entries and the mask INIT_LIST_HEAD(&mount_hashtable[u]);
* 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(); err = sysfs_init();
if (err) if (err)
printk(KERN_WARNING "%s: sysfs_init error: %d\n", printk(KERN_WARNING "%s: sysfs_init error: %d\n",