Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 390c6843 authored by Ram Pai's avatar Ram Pai Committed by Linus Torvalds
Browse files

[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: default avatarMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: default avatarRam Pai <linuxram@us.ibm.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 36341f64

fs/namespace.c

+23 −23
Original line number Diff line number Diff line
@@ -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 @@ static int do_move_mount(struct nameidata *nd, char *old_name) 
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);

}

include/linux/namespace.h

+0 −1
Original line number Diff line number Diff line
@@ -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;

};