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Commit fedc1ed0 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 

Pull vfs fixes from Al Viro:
 "Switch mnt_hash to hlist, turning the races between __lookup_mnt() and
  hash modifications into false negatives from __lookup_mnt() (instead
  of hangs)"

On the false negatives from __lookup_mnt():
 "The *only* thing we care about is not getting stuck in __lookup_mnt().
  If it misses an entry because something in front of it just got moved
  around, etc, we are fine.  We'll notice that mount_lock mismatch and
  that'll be it"

* 'for-linus-2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  switch mnt_hash to hlist
  don't bother with propagate_mnt() unless the target is shared
  keep shadowed vfsmounts together
  resizable namespace.c hashes
parents 01358e56 38129a13

fs/mount.h

+2 −2
Original line number Diff line number Diff line
@@ -19,13 +19,13 @@ struct mnt_pcp { 
};



struct mountpoint {

	struct list_head m_hash;

	struct hlist_node m_hash;

	struct dentry *m_dentry;

	int m_count;

};



struct mount {

	struct list_head mnt_hash;

	struct hlist_node mnt_hash;

	struct mount *mnt_parent;

	struct dentry *mnt_mountpoint;

	struct vfsmount mnt;

fs/namespace.c

+115 −62
Original line number Diff line number Diff line
@@ -23,11 +23,34 @@ 
#include <linux/uaccess.h>

#include <linux/proc_ns.h>

#include <linux/magic.h>

#include <linux/bootmem.h>

#include "pnode.h"

#include "internal.h"



#define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head))

#define HASH_SIZE (1UL << HASH_SHIFT)

static unsigned int m_hash_mask __read_mostly;

static unsigned int m_hash_shift __read_mostly;

static unsigned int mp_hash_mask __read_mostly;

static unsigned int mp_hash_shift __read_mostly;



static __initdata unsigned long mhash_entries;

static int __init set_mhash_entries(char *str)

{

	if (!str)

		return 0;

	mhash_entries = simple_strtoul(str, &str, 0);

	return 1;

}

__setup("mhash_entries=", set_mhash_entries);



static __initdata unsigned long mphash_entries;

static int __init set_mphash_entries(char *str)

{

	if (!str)

		return 0;

	mphash_entries = simple_strtoul(str, &str, 0);

	return 1;

}

__setup("mphash_entries=", set_mphash_entries);



static int event;

static DEFINE_IDA(mnt_id_ida);
@@ -36,8 +59,8 @@ static DEFINE_SPINLOCK(mnt_id_lock); 
static int mnt_id_start = 0;

static int mnt_group_start = 1;



static struct list_head *mount_hashtable __read_mostly;

static struct list_head *mountpoint_hashtable __read_mostly;

static struct hlist_head *mount_hashtable __read_mostly;

static struct hlist_head *mountpoint_hashtable __read_mostly;

static struct kmem_cache *mnt_cache __read_mostly;

static DECLARE_RWSEM(namespace_sem);
@@ -55,12 +78,19 @@ EXPORT_SYMBOL_GPL(fs_kobj); 
 */

__cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock);



static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)

static inline struct hlist_head *m_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_SHIFT);

	return tmp & (HASH_SIZE - 1);

	tmp = tmp + (tmp >> m_hash_shift);

	return &mount_hashtable[tmp & m_hash_mask];

}



static inline struct hlist_head *mp_hash(struct dentry *dentry)

{

	unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES);

	tmp = tmp + (tmp >> mp_hash_shift);

	return &mountpoint_hashtable[tmp & mp_hash_mask];

}



/*
@@ -187,7 +217,7 @@ static struct mount *alloc_vfsmnt(const char *name) 
		mnt->mnt_writers = 0;

#endif



		INIT_LIST_HEAD(&mnt->mnt_hash);

		INIT_HLIST_NODE(&mnt->mnt_hash);

		INIT_LIST_HEAD(&mnt->mnt_child);

		INIT_LIST_HEAD(&mnt->mnt_mounts);

		INIT_LIST_HEAD(&mnt->mnt_list);
@@ -575,10 +605,10 @@ bool legitimize_mnt(struct vfsmount *bastard, unsigned seq) 
 */

struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)

{

	struct list_head *head = mount_hashtable + hash(mnt, dentry);

	struct hlist_head *head = m_hash(mnt, dentry);

	struct mount *p;



	list_for_each_entry_rcu(p, head, mnt_hash)

	hlist_for_each_entry_rcu(p, head, mnt_hash)

		if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)

			return p;

	return NULL;
@@ -590,13 +620,17 @@ struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry) 
 */

struct mount *__lookup_mnt_last(struct vfsmount *mnt, struct dentry *dentry)

{

	struct list_head *head = mount_hashtable + hash(mnt, dentry);

	struct mount *p;



	list_for_each_entry_reverse(p, head, mnt_hash)

		if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)

			return p;

	return NULL;

	struct mount *p, *res;

	res = p = __lookup_mnt(mnt, dentry);

	if (!p)

		goto out;

	hlist_for_each_entry_continue(p, mnt_hash) {

		if (&p->mnt_parent->mnt != mnt || p->mnt_mountpoint != dentry)

			break;

		res = p;

	}

out:

	return res;

}



/*
@@ -633,11 +667,11 @@ struct vfsmount *lookup_mnt(struct path *path) 


static struct mountpoint *new_mountpoint(struct dentry *dentry)

{

	struct list_head *chain = mountpoint_hashtable + hash(NULL, dentry);

	struct hlist_head *chain = mp_hash(dentry);

	struct mountpoint *mp;

	int ret;



	list_for_each_entry(mp, chain, m_hash) {

	hlist_for_each_entry(mp, chain, m_hash) {

		if (mp->m_dentry == dentry) {

			/* might be worth a WARN_ON() */

			if (d_unlinked(dentry))
@@ -659,7 +693,7 @@ static struct mountpoint *new_mountpoint(struct dentry *dentry) 


	mp->m_dentry = dentry;

	mp->m_count = 1;

	list_add(&mp->m_hash, chain);

	hlist_add_head(&mp->m_hash, chain);

	return mp;

}
@@ -670,7 +704,7 @@ static void put_mountpoint(struct mountpoint *mp) 
		spin_lock(&dentry->d_lock);

		dentry->d_flags &= ~DCACHE_MOUNTED;

		spin_unlock(&dentry->d_lock);

		list_del(&mp->m_hash);

		hlist_del(&mp->m_hash);

		kfree(mp);

	}

}
@@ -712,7 +746,7 @@ static void detach_mnt(struct mount *mnt, struct path *old_path) 
	mnt->mnt_parent = mnt;

	mnt->mnt_mountpoint = mnt->mnt.mnt_root;

	list_del_init(&mnt->mnt_child);

	list_del_init(&mnt->mnt_hash);

	hlist_del_init_rcu(&mnt->mnt_hash);

	put_mountpoint(mnt->mnt_mp);

	mnt->mnt_mp = NULL;

}
@@ -739,15 +773,14 @@ static void attach_mnt(struct mount *mnt, 
			struct mountpoint *mp)

{

	mnt_set_mountpoint(parent, mp, mnt);

	list_add_tail(&mnt->mnt_hash, mount_hashtable +

			hash(&parent->mnt, mp->m_dentry));

	hlist_add_head_rcu(&mnt->mnt_hash, m_hash(&parent->mnt, mp->m_dentry));

	list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);

}



/*

 * vfsmount lock must be held for write

 */

static void commit_tree(struct mount *mnt)

static void commit_tree(struct mount *mnt, struct mount *shadows)

{

	struct mount *parent = mnt->mnt_parent;

	struct mount *m;
@@ -762,8 +795,11 @@ static void commit_tree(struct mount *mnt) 


	list_splice(&head, n->list.prev);



	list_add_tail(&mnt->mnt_hash, mount_hashtable +

				hash(&parent->mnt, mnt->mnt_mountpoint));

	if (shadows)

		hlist_add_after_rcu(&shadows->mnt_hash, &mnt->mnt_hash);

	else

		hlist_add_head_rcu(&mnt->mnt_hash,

				m_hash(&parent->mnt, mnt->mnt_mountpoint));

	list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);

	touch_mnt_namespace(n);

}
@@ -1153,26 +1189,28 @@ int may_umount(struct vfsmount *mnt) 


EXPORT_SYMBOL(may_umount);



static LIST_HEAD(unmounted);	/* protected by namespace_sem */

static HLIST_HEAD(unmounted);	/* protected by namespace_sem */



static void namespace_unlock(void)

{

	struct mount *mnt;

	LIST_HEAD(head);

	struct hlist_head head = unmounted;



	if (likely(list_empty(&unmounted))) {

	if (likely(hlist_empty(&head))) {

		up_write(&namespace_sem);

		return;

	}



	list_splice_init(&unmounted, &head);

	head.first->pprev = &head.first;

	INIT_HLIST_HEAD(&unmounted);



	up_write(&namespace_sem);



	synchronize_rcu();



	while (!list_empty(&head)) {

		mnt = list_first_entry(&head, struct mount, mnt_hash);

		list_del_init(&mnt->mnt_hash);

	while (!hlist_empty(&head)) {

		mnt = hlist_entry(head.first, struct mount, mnt_hash);

		hlist_del_init(&mnt->mnt_hash);

		if (mnt->mnt_ex_mountpoint.mnt)

			path_put(&mnt->mnt_ex_mountpoint);

		mntput(&mnt->mnt);
@@ -1193,16 +1231,19 @@ static inline void namespace_lock(void) 
 */

void umount_tree(struct mount *mnt, int how)

{

	LIST_HEAD(tmp_list);

	HLIST_HEAD(tmp_list);

	struct mount *p;

	struct mount *last = NULL;



	for (p = mnt; p; p = next_mnt(p, mnt))

		list_move(&p->mnt_hash, &tmp_list);

	for (p = mnt; p; p = next_mnt(p, mnt)) {

		hlist_del_init_rcu(&p->mnt_hash);

		hlist_add_head(&p->mnt_hash, &tmp_list);

	}



	if (how)

		propagate_umount(&tmp_list);



	list_for_each_entry(p, &tmp_list, mnt_hash) {

	hlist_for_each_entry(p, &tmp_list, mnt_hash) {

		list_del_init(&p->mnt_expire);

		list_del_init(&p->mnt_list);

		__touch_mnt_namespace(p->mnt_ns);
@@ -1220,8 +1261,13 @@ void umount_tree(struct mount *mnt, int how) 
			p->mnt_mp = NULL;

		}

		change_mnt_propagation(p, MS_PRIVATE);

		last = p;

	}

	if (last) {

		last->mnt_hash.next = unmounted.first;

		unmounted.first = tmp_list.first;

		unmounted.first->pprev = &unmounted.first;

	}

	list_splice(&tmp_list, &unmounted);

}



static void shrink_submounts(struct mount *mnt);
@@ -1605,24 +1651,23 @@ static int attach_recursive_mnt(struct mount *source_mnt, 
			struct mountpoint *dest_mp,

			struct path *parent_path)

{

	LIST_HEAD(tree_list);

	HLIST_HEAD(tree_list);

	struct mount *child, *p;

	struct hlist_node *n;

	int err;



	if (IS_MNT_SHARED(dest_mnt)) {

		err = invent_group_ids(source_mnt, true);

		if (err)

			goto out;

	}

		err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);

		if (err)

			goto out_cleanup_ids;



		lock_mount_hash();



	if (IS_MNT_SHARED(dest_mnt)) {

		for (p = source_mnt; p; p = next_mnt(p, source_mnt))

			set_mnt_shared(p);

	} else {

		lock_mount_hash();

	}

	if (parent_path) {

		detach_mnt(source_mnt, parent_path);
@@ -1630,19 +1675,21 @@ static int attach_recursive_mnt(struct mount *source_mnt, 
		touch_mnt_namespace(source_mnt->mnt_ns);

	} else {

		mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);

		commit_tree(source_mnt);

		commit_tree(source_mnt, NULL);

	}



	list_for_each_entry_safe(child, p, &tree_list, mnt_hash) {

		list_del_init(&child->mnt_hash);

		commit_tree(child);

	hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) {

		struct mount *q;

		hlist_del_init(&child->mnt_hash);

		q = __lookup_mnt_last(&child->mnt_parent->mnt,

				      child->mnt_mountpoint);

		commit_tree(child, q);

	}

	unlock_mount_hash();



	return 0;



 out_cleanup_ids:

	if (IS_MNT_SHARED(dest_mnt))

	cleanup_group_ids(source_mnt, NULL);

 out:

	return err;
@@ -2777,18 +2824,24 @@ void __init mnt_init(void) 
	mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),

			0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);



	mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);

	mountpoint_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);

	mount_hashtable = alloc_large_system_hash("Mount-cache",

				sizeof(struct hlist_head),

				mhash_entries, 19,

				0,

				&m_hash_shift, &m_hash_mask, 0, 0);

	mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache",

				sizeof(struct hlist_head),

				mphash_entries, 19,

				0,

				&mp_hash_shift, &mp_hash_mask, 0, 0);



	if (!mount_hashtable || !mountpoint_hashtable)

		panic("Failed to allocate mount hash table\n");



	printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE);



	for (u = 0; u < HASH_SIZE; u++)

		INIT_LIST_HEAD(&mount_hashtable[u]);

	for (u = 0; u < HASH_SIZE; u++)

		INIT_LIST_HEAD(&mountpoint_hashtable[u]);

	for (u = 0; u <= m_hash_mask; u++)

		INIT_HLIST_HEAD(&mount_hashtable[u]);

	for (u = 0; u <= mp_hash_mask; u++)

		INIT_HLIST_HEAD(&mountpoint_hashtable[u]);



	kernfs_init();

fs/pnode.c

+15 −11
Original line number Diff line number Diff line
@@ -220,14 +220,14 @@ static struct mount *get_source(struct mount *dest, 
 * @tree_list : list of heads of trees to be attached.

 */

int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp,

		    struct mount *source_mnt, struct list_head *tree_list)

		    struct mount *source_mnt, struct hlist_head *tree_list)

{

	struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;

	struct mount *m, *child;

	int ret = 0;

	struct mount *prev_dest_mnt = dest_mnt;

	struct mount *prev_src_mnt  = source_mnt;

	LIST_HEAD(tmp_list);

	HLIST_HEAD(tmp_list);



	for (m = propagation_next(dest_mnt, dest_mnt); m;

			m = propagation_next(m, dest_mnt)) {
@@ -246,27 +246,29 @@ int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp, 
		child = copy_tree(source, source->mnt.mnt_root, type);

		if (IS_ERR(child)) {

			ret = PTR_ERR(child);

			list_splice(tree_list, tmp_list.prev);

			tmp_list = *tree_list;

			tmp_list.first->pprev = &tmp_list.first;

			INIT_HLIST_HEAD(tree_list);

			goto out;

		}



		if (is_subdir(dest_mp->m_dentry, m->mnt.mnt_root)) {

			mnt_set_mountpoint(m, dest_mp, child);

			list_add_tail(&child->mnt_hash, tree_list);

			hlist_add_head(&child->mnt_hash, tree_list);

		} else {

			/*

			 * This can happen if the parent mount was bind mounted

			 * on some subdirectory of a shared/slave mount.

			 */

			list_add_tail(&child->mnt_hash, &tmp_list);

			hlist_add_head(&child->mnt_hash, &tmp_list);

		}

		prev_dest_mnt = m;

		prev_src_mnt  = child;

	}

out:

	lock_mount_hash();

	while (!list_empty(&tmp_list)) {

		child = list_first_entry(&tmp_list, struct mount, mnt_hash);

	while (!hlist_empty(&tmp_list)) {

		child = hlist_entry(tmp_list.first, struct mount, mnt_hash);

		umount_tree(child, 0);

	}

	unlock_mount_hash();
@@ -338,8 +340,10 @@ static void __propagate_umount(struct mount *mnt) 
		 * umount the child only if the child has no

		 * other children

		 */

		if (child && list_empty(&child->mnt_mounts))

			list_move_tail(&child->mnt_hash, &mnt->mnt_hash);

		if (child && list_empty(&child->mnt_mounts)) {

			hlist_del_init_rcu(&child->mnt_hash);

			hlist_add_before_rcu(&child->mnt_hash, &mnt->mnt_hash);

		}

	}

}
@@ -350,11 +354,11 @@ static void __propagate_umount(struct mount *mnt) 
 *

 * vfsmount lock must be held for write

 */

int propagate_umount(struct list_head *list)

int propagate_umount(struct hlist_head *list)

{

	struct mount *mnt;



	list_for_each_entry(mnt, list, mnt_hash)

	hlist_for_each_entry(mnt, list, mnt_hash)

		__propagate_umount(mnt);

	return 0;

}

fs/pnode.h

+2 −2
Original line number Diff line number Diff line
@@ -36,8 +36,8 @@ static inline void set_mnt_shared(struct mount *mnt) 


void change_mnt_propagation(struct mount *, int);

int propagate_mnt(struct mount *, struct mountpoint *, struct mount *,

		struct list_head *);

int propagate_umount(struct list_head *);

		struct hlist_head *);

int propagate_umount(struct hlist_head *);

int propagate_mount_busy(struct mount *, int);

void mnt_release_group_id(struct mount *);

int get_dominating_id(struct mount *mnt, const struct path *root);