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Commit 13f14b4d authored by Eric Dumazet's avatar Eric Dumazet Committed by Linus Torvalds
Browse files

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: default avatarEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b41ecbeb

fs/namespace.c

+11 −34
Original line number Diff line number Diff line
@@ -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",