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[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>
This commit is contained in:
Ram Pai 2005-11-07 17:17:51 -05:00 committed by Linus Torvalds
parent 36341f6456
commit 390c684367
2 changed files with 23 additions and 24 deletions
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46
fs/namespace.c
View File

@ -46,6 +46,7 @@ static int event;
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 @@ static void *m_start(struct seq_file *m, loff_t *pos)
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_next(struct seq_file *m, void *v, loff_t *pos)
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 @@ static int do_umount(struct vfsmount *mnt, int flags)
return retval;
}
down_write(&current->namespace->sem);
down_write(&namespace_sem);
spin_lock(&vfsmount_lock);
event++;
@ -500,7 +500,7 @@ static int do_umount(struct vfsmount *mnt, int flags)
spin_unlock(&vfsmount_lock);
if (retval)
security_sb_umount_busy(mnt);
up_write(&current->namespace->sem);
up_write(&namespace_sem);
release_mounts(&umount_list);
return retval;
}
@ -678,7 +678,7 @@ static int do_loopback(struct nameidata *nd, char *old_name, int recurse)
if (err)
return err;
down_write(&current->namespace->sem);
down_write(&namespace_sem);
err = -EINVAL;
if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt))
goto out;
@ -702,7 +702,7 @@ static int do_loopback(struct nameidata *nd, char *old_name, int recurse)
}
out:
up_write(&current->namespace->sem);
up_write(&namespace_sem);
path_release(&old_nd);
return err;
}
@ -750,7 +750,7 @@ static int do_move_mount(struct nameidata *nd, char *old_name)
if (err)
return err;
down_write(&current->namespace->sem);
down_write(&namespace_sem);
while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
;
err = -EINVAL;
@ -795,7 +795,7 @@ out2:
out1:
up(&nd->dentry->d_inode->i_sem);
out:
up_write(&current->namespace->sem);
up_write(&namespace_sem);
if (!err)
path_release(&parent_nd);
path_release(&old_nd);
@ -834,7 +834,7 @@ int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd,
{
int err;
down_write(&current->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 @@ int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd,
list_add_tail(&newmnt->mnt_expire, fslist);
spin_unlock(&vfsmount_lock);
}
up_write(&current->namespace->sem);
up_write(&namespace_sem);
return 0;
unlock:
up_write(&current->namespace->sem);
up_write(&namespace_sem);
mntput(newmnt);
return err;
}
@ -958,9 +958,9 @@ void mark_mounts_for_expiry(struct list_head *mounts)
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 @@ int copy_namespace(int flags, struct task_struct *tsk)
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 @@ int copy_namespace(int flags, struct task_struct *tsk)
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 @@ asmlinkage long sys_pivot_root(const char __user * new_root,
user_nd.mnt = mntget(current->fs->rootmnt);
user_nd.dentry = dget(current->fs->root);
read_unlock(&current->fs->lock);
down_write(&current->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 @@ asmlinkage long sys_pivot_root(const char __user * new_root,
path_release(&parent_nd);
out2:
up(&old_nd.dentry->d_inode->i_sem);
up_write(&current->namespace->sem);
up_write(&namespace_sem);
path_release(&user_nd);
path_release(&old_nd);
out1:
@ -1434,7 +1433,6 @@ static void __init init_mount_tree(void)
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 @@ void __init mnt_init(unsigned long mempages)
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 @@ void __put_namespace(struct namespace *namespace)
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);
}

1
include/linux/namespace.h
View File

@ -9,7 +9,6 @@ struct namespace {
atomic_t count;
struct vfsmount * root;
struct list_head list;
struct rw_semaphore sem;
wait_queue_head_t poll;
int event;
};