[PATCH] making namespace_sem global
This removes the per-namespace semaphore in favor of a global semaphore.
This can have an effect on namespace scalability.
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/namespace.c b/fs/namespace.c
index 65f9c0e..4abee9a 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -46,6 +46,7 @@
static struct list_head *mount_hashtable;
static int hash_mask __read_mostly, hash_bits __read_mostly;
static kmem_cache_t *mnt_cache;
+static struct rw_semaphore namespace_sem;
static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
{
@@ -250,7 +251,7 @@
struct list_head *p;
loff_t l = *pos;
- down_read(&n->sem);
+ down_read(&namespace_sem);
list_for_each(p, &n->list)
if (!l--)
return list_entry(p, struct vfsmount, mnt_list);
@@ -267,8 +268,7 @@
static void m_stop(struct seq_file *m, void *v)
{
- struct namespace *n = m->private;
- up_read(&n->sem);
+ up_read(&namespace_sem);
}
static inline void mangle(struct seq_file *m, const char *s)
@@ -487,7 +487,7 @@
return retval;
}
- down_write(¤t->namespace->sem);
+ down_write(&namespace_sem);
spin_lock(&vfsmount_lock);
event++;
@@ -500,7 +500,7 @@
spin_unlock(&vfsmount_lock);
if (retval)
security_sb_umount_busy(mnt);
- up_write(¤t->namespace->sem);
+ up_write(&namespace_sem);
release_mounts(&umount_list);
return retval;
}
@@ -678,7 +678,7 @@
if (err)
return err;
- down_write(¤t->namespace->sem);
+ down_write(&namespace_sem);
err = -EINVAL;
if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt))
goto out;
@@ -702,7 +702,7 @@
}
out:
- up_write(¤t->namespace->sem);
+ up_write(&namespace_sem);
path_release(&old_nd);
return err;
}
@@ -750,7 +750,7 @@
if (err)
return err;
- down_write(¤t->namespace->sem);
+ down_write(&namespace_sem);
while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
;
err = -EINVAL;
@@ -795,7 +795,7 @@
out1:
up(&nd->dentry->d_inode->i_sem);
out:
- up_write(¤t->namespace->sem);
+ up_write(&namespace_sem);
if (!err)
path_release(&parent_nd);
path_release(&old_nd);
@@ -834,7 +834,7 @@
{
int err;
- down_write(¤t->namespace->sem);
+ down_write(&namespace_sem);
/* Something was mounted here while we slept */
while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
;
@@ -862,11 +862,11 @@
list_add_tail(&newmnt->mnt_expire, fslist);
spin_unlock(&vfsmount_lock);
}
- up_write(¤t->namespace->sem);
+ up_write(&namespace_sem);
return 0;
unlock:
- up_write(¤t->namespace->sem);
+ up_write(&namespace_sem);
mntput(newmnt);
return err;
}
@@ -958,9 +958,9 @@
get_namespace(namespace);
spin_unlock(&vfsmount_lock);
- down_write(&namespace->sem);
+ down_write(&namespace_sem);
expire_mount(mnt, mounts, &umounts);
- up_write(&namespace->sem);
+ up_write(&namespace_sem);
release_mounts(&umounts);
mntput(mnt);
put_namespace(namespace);
@@ -1127,17 +1127,16 @@
goto out;
atomic_set(&new_ns->count, 1);
- init_rwsem(&new_ns->sem);
INIT_LIST_HEAD(&new_ns->list);
init_waitqueue_head(&new_ns->poll);
new_ns->event = 0;
- down_write(&tsk->namespace->sem);
+ down_write(&namespace_sem);
/* First pass: copy the tree topology */
new_ns->root = copy_tree(namespace->root, namespace->root->mnt_root,
CL_EXPIRE);
if (!new_ns->root) {
- up_write(&tsk->namespace->sem);
+ up_write(&namespace_sem);
kfree(new_ns);
goto out;
}
@@ -1171,7 +1170,7 @@
p = next_mnt(p, namespace->root);
q = next_mnt(q, new_ns->root);
}
- up_write(&tsk->namespace->sem);
+ up_write(&namespace_sem);
tsk->namespace = new_ns;
@@ -1356,7 +1355,7 @@
user_nd.mnt = mntget(current->fs->rootmnt);
user_nd.dentry = dget(current->fs->root);
read_unlock(¤t->fs->lock);
- down_write(¤t->namespace->sem);
+ down_write(&namespace_sem);
down(&old_nd.dentry->d_inode->i_sem);
error = -EINVAL;
if (!check_mnt(user_nd.mnt))
@@ -1407,7 +1406,7 @@
path_release(&parent_nd);
out2:
up(&old_nd.dentry->d_inode->i_sem);
- up_write(¤t->namespace->sem);
+ up_write(&namespace_sem);
path_release(&user_nd);
path_release(&old_nd);
out1:
@@ -1434,7 +1433,6 @@
panic("Can't allocate initial namespace");
atomic_set(&namespace->count, 1);
INIT_LIST_HEAD(&namespace->list);
- init_rwsem(&namespace->sem);
init_waitqueue_head(&namespace->poll);
namespace->event = 0;
list_add(&mnt->mnt_list, &namespace->list);
@@ -1459,6 +1457,8 @@
unsigned int nr_hash;
int i;
+ init_rwsem(&namespace_sem);
+
mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount),
0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL, NULL);
@@ -1507,11 +1507,11 @@
LIST_HEAD(umount_list);
namespace->root = NULL;
spin_unlock(&vfsmount_lock);
- down_write(&namespace->sem);
+ down_write(&namespace_sem);
spin_lock(&vfsmount_lock);
umount_tree(root, &umount_list);
spin_unlock(&vfsmount_lock);
- up_write(&namespace->sem);
+ up_write(&namespace_sem);
release_mounts(&umount_list);
kfree(namespace);
}
diff --git a/include/linux/namespace.h b/include/linux/namespace.h
index 6f0f25d..6731977 100644
--- a/include/linux/namespace.h
+++ b/include/linux/namespace.h
@@ -9,7 +9,6 @@
atomic_t count;
struct vfsmount * root;
struct list_head list;
- struct rw_semaphore sem;
wait_queue_head_t poll;
int event;
};