get rid of full-hash scan on detaching vfsmounts
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/mount.h b/fs/mount.h
index cd50079..64a8581 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -18,6 +18,12 @@
int mnt_writers;
};
+struct mountpoint {
+ struct list_head m_hash;
+ struct dentry *m_dentry;
+ int m_count;
+};
+
struct mount {
struct list_head mnt_hash;
struct mount *mnt_parent;
@@ -40,6 +46,7 @@
struct list_head mnt_slave; /* slave list entry */
struct mount *mnt_master; /* slave is on master->mnt_slave_list */
struct mnt_namespace *mnt_ns; /* containing namespace */
+ struct mountpoint *mnt_mp; /* where is it mounted */
#ifdef CONFIG_FSNOTIFY
struct hlist_head mnt_fsnotify_marks;
__u32 mnt_fsnotify_mask;
diff --git a/fs/namespace.c b/fs/namespace.c
index 6c7d31e..d7bb5a55 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -36,6 +36,7 @@
static int mnt_group_start = 1;
static struct list_head *mount_hashtable __read_mostly;
+static struct list_head *mountpoint_hashtable __read_mostly;
static struct kmem_cache *mnt_cache __read_mostly;
static struct rw_semaphore namespace_sem;
@@ -605,6 +606,51 @@
}
}
+static struct mountpoint *new_mountpoint(struct dentry *dentry)
+{
+ struct list_head *chain = mountpoint_hashtable + hash(NULL, dentry);
+ struct mountpoint *mp;
+
+ list_for_each_entry(mp, chain, m_hash) {
+ if (mp->m_dentry == dentry) {
+ /* might be worth a WARN_ON() */
+ if (d_unlinked(dentry))
+ return ERR_PTR(-ENOENT);
+ mp->m_count++;
+ return mp;
+ }
+ }
+
+ mp = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
+ if (!mp)
+ return ERR_PTR(-ENOMEM);
+
+ spin_lock(&dentry->d_lock);
+ if (d_unlinked(dentry)) {
+ spin_unlock(&dentry->d_lock);
+ kfree(mp);
+ return ERR_PTR(-ENOENT);
+ }
+ dentry->d_flags |= DCACHE_MOUNTED;
+ spin_unlock(&dentry->d_lock);
+ mp->m_dentry = dentry;
+ mp->m_count = 1;
+ list_add(&mp->m_hash, chain);
+ return mp;
+}
+
+static void put_mountpoint(struct mountpoint *mp)
+{
+ if (!--mp->m_count) {
+ struct dentry *dentry = mp->m_dentry;
+ spin_lock(&dentry->d_lock);
+ dentry->d_flags &= ~DCACHE_MOUNTED;
+ spin_unlock(&dentry->d_lock);
+ list_del(&mp->m_hash);
+ kfree(mp);
+ }
+}
+
static inline int check_mnt(struct mount *mnt)
{
return mnt->mnt_ns == current->nsproxy->mnt_ns;
@@ -633,27 +679,6 @@
}
/*
- * Clear dentry's mounted state if it has no remaining mounts.
- * vfsmount_lock must be held for write.
- */
-static void dentry_reset_mounted(struct dentry *dentry)
-{
- unsigned u;
-
- for (u = 0; u < HASH_SIZE; u++) {
- struct mount *p;
-
- list_for_each_entry(p, &mount_hashtable[u], mnt_hash) {
- if (p->mnt_mountpoint == dentry)
- return;
- }
- }
- spin_lock(&dentry->d_lock);
- dentry->d_flags &= ~DCACHE_MOUNTED;
- spin_unlock(&dentry->d_lock);
-}
-
-/*
* vfsmount lock must be held for write
*/
static void detach_mnt(struct mount *mnt, struct path *old_path)
@@ -664,32 +689,35 @@
mnt->mnt_mountpoint = mnt->mnt.mnt_root;
list_del_init(&mnt->mnt_child);
list_del_init(&mnt->mnt_hash);
- dentry_reset_mounted(old_path->dentry);
+ put_mountpoint(mnt->mnt_mp);
+ mnt->mnt_mp = NULL;
}
/*
* vfsmount lock must be held for write
*/
-void mnt_set_mountpoint(struct mount *mnt, struct dentry *dentry,
+void mnt_set_mountpoint(struct mount *mnt,
+ struct mountpoint *mp,
struct mount *child_mnt)
{
+ mp->m_count++;
mnt_add_count(mnt, 1); /* essentially, that's mntget */
- child_mnt->mnt_mountpoint = dget(dentry);
+ child_mnt->mnt_mountpoint = dget(mp->m_dentry);
child_mnt->mnt_parent = mnt;
- spin_lock(&dentry->d_lock);
- dentry->d_flags |= DCACHE_MOUNTED;
- spin_unlock(&dentry->d_lock);
+ child_mnt->mnt_mp = mp;
}
/*
* vfsmount lock must be held for write
*/
-static void attach_mnt(struct mount *mnt, struct path *path)
+static void attach_mnt(struct mount *mnt,
+ struct mount *parent,
+ struct mountpoint *mp)
{
- mnt_set_mountpoint(real_mount(path->mnt), path->dentry, mnt);
+ mnt_set_mountpoint(parent, mp, mnt);
list_add_tail(&mnt->mnt_hash, mount_hashtable +
- hash(path->mnt, path->dentry));
- list_add_tail(&mnt->mnt_child, &real_mount(path->mnt)->mnt_mounts);
+ hash(&parent->mnt, mp->m_dentry));
+ list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
}
/*
@@ -1138,7 +1166,8 @@
list_del_init(&p->mnt_child);
if (mnt_has_parent(p)) {
p->mnt_parent->mnt_ghosts++;
- dentry_reset_mounted(p->mnt_mountpoint);
+ put_mountpoint(p->mnt_mp);
+ p->mnt_mp = NULL;
}
change_mnt_propagation(p, MS_PRIVATE);
}
@@ -1323,8 +1352,7 @@
struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
int flag)
{
- struct mount *res, *p, *q, *r;
- struct path path;
+ struct mount *res, *p, *q, *r, *parent;
if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
return ERR_PTR(-EINVAL);
@@ -1351,14 +1379,13 @@
q = q->mnt_parent;
}
p = s;
- path.mnt = &q->mnt;
- path.dentry = p->mnt_mountpoint;
+ parent = q;
q = clone_mnt(p, p->mnt.mnt_root, flag);
if (IS_ERR(q))
goto out;
br_write_lock(&vfsmount_lock);
list_add_tail(&q->mnt_list, &res->mnt_list);
- attach_mnt(q, &path);
+ attach_mnt(q, parent, p->mnt_mp);
br_write_unlock(&vfsmount_lock);
}
}
@@ -1505,11 +1532,11 @@
* in allocations.
*/
static int attach_recursive_mnt(struct mount *source_mnt,
- struct path *path, struct path *parent_path)
+ struct mount *dest_mnt,
+ struct mountpoint *dest_mp,
+ struct path *parent_path)
{
LIST_HEAD(tree_list);
- struct mount *dest_mnt = real_mount(path->mnt);
- struct dentry *dest_dentry = path->dentry;
struct mount *child, *p;
int err;
@@ -1518,7 +1545,7 @@
if (err)
goto out;
}
- err = propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list);
+ err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
if (err)
goto out_cleanup_ids;
@@ -1530,10 +1557,10 @@
}
if (parent_path) {
detach_mnt(source_mnt, parent_path);
- attach_mnt(source_mnt, path);
+ attach_mnt(source_mnt, dest_mnt, dest_mp);
touch_mnt_namespace(source_mnt->mnt_ns);
} else {
- mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt);
+ mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
commit_tree(source_mnt);
}
@@ -1552,46 +1579,53 @@
return err;
}
-static int lock_mount(struct path *path)
+static struct mountpoint *lock_mount(struct path *path)
{
struct vfsmount *mnt;
+ struct dentry *dentry = path->dentry;
retry:
- mutex_lock(&path->dentry->d_inode->i_mutex);
- if (unlikely(cant_mount(path->dentry))) {
- mutex_unlock(&path->dentry->d_inode->i_mutex);
- return -ENOENT;
+ mutex_lock(&dentry->d_inode->i_mutex);
+ if (unlikely(cant_mount(dentry))) {
+ mutex_unlock(&dentry->d_inode->i_mutex);
+ return ERR_PTR(-ENOENT);
}
down_write(&namespace_sem);
mnt = lookup_mnt(path);
- if (likely(!mnt))
- return 0;
+ if (likely(!mnt)) {
+ struct mountpoint *mp = new_mountpoint(dentry);
+ if (IS_ERR(mp)) {
+ up_write(&namespace_sem);
+ mutex_unlock(&dentry->d_inode->i_mutex);
+ return mp;
+ }
+ return mp;
+ }
up_write(&namespace_sem);
mutex_unlock(&path->dentry->d_inode->i_mutex);
path_put(path);
path->mnt = mnt;
- path->dentry = dget(mnt->mnt_root);
+ dentry = path->dentry = dget(mnt->mnt_root);
goto retry;
}
-static void unlock_mount(struct path *path)
+static void unlock_mount(struct mountpoint *where)
{
+ struct dentry *dentry = where->m_dentry;
+ put_mountpoint(where);
up_write(&namespace_sem);
- mutex_unlock(&path->dentry->d_inode->i_mutex);
+ mutex_unlock(&dentry->d_inode->i_mutex);
}
-static int graft_tree(struct mount *mnt, struct path *path)
+static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp)
{
if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER)
return -EINVAL;
- if (S_ISDIR(path->dentry->d_inode->i_mode) !=
+ if (S_ISDIR(mp->m_dentry->d_inode->i_mode) !=
S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode))
return -ENOTDIR;
- if (d_unlinked(path->dentry))
- return -ENOENT;
-
- return attach_recursive_mnt(mnt, path, NULL);
+ return attach_recursive_mnt(mnt, p, mp, NULL);
}
/*
@@ -1654,7 +1688,8 @@
{
LIST_HEAD(umount_list);
struct path old_path;
- struct mount *mnt = NULL, *old;
+ struct mount *mnt = NULL, *old, *parent;
+ struct mountpoint *mp;
int err;
if (!old_name || !*old_name)
return -EINVAL;
@@ -1666,17 +1701,19 @@
if (mnt_ns_loop(&old_path))
goto out;
- err = lock_mount(path);
- if (err)
+ mp = lock_mount(path);
+ err = PTR_ERR(mp);
+ if (IS_ERR(mp))
goto out;
old = real_mount(old_path.mnt);
+ parent = real_mount(path->mnt);
err = -EINVAL;
if (IS_MNT_UNBINDABLE(old))
goto out2;
- if (!check_mnt(real_mount(path->mnt)) || !check_mnt(old))
+ if (!check_mnt(parent) || !check_mnt(old))
goto out2;
if (recurse)
@@ -1689,14 +1726,14 @@
goto out2;
}
- err = graft_tree(mnt, path);
+ err = graft_tree(mnt, parent, mp);
if (err) {
br_write_lock(&vfsmount_lock);
umount_tree(mnt, 0, &umount_list);
br_write_unlock(&vfsmount_lock);
}
out2:
- unlock_mount(path);
+ unlock_mount(mp);
release_mounts(&umount_list);
out:
path_put(&old_path);
@@ -1779,6 +1816,7 @@
struct path old_path, parent_path;
struct mount *p;
struct mount *old;
+ struct mountpoint *mp;
int err;
if (!old_name || !*old_name)
return -EINVAL;
@@ -1786,8 +1824,9 @@
if (err)
return err;
- err = lock_mount(path);
- if (err < 0)
+ mp = lock_mount(path);
+ err = PTR_ERR(mp);
+ if (IS_ERR(mp))
goto out;
old = real_mount(old_path.mnt);
@@ -1797,9 +1836,6 @@
if (!check_mnt(p) || !check_mnt(old))
goto out1;
- if (d_unlinked(path->dentry))
- goto out1;
-
err = -EINVAL;
if (old_path.dentry != old_path.mnt->mnt_root)
goto out1;
@@ -1826,7 +1862,7 @@
if (p == old)
goto out1;
- err = attach_recursive_mnt(old, path, &parent_path);
+ err = attach_recursive_mnt(old, real_mount(path->mnt), mp, &parent_path);
if (err)
goto out1;
@@ -1834,7 +1870,7 @@
* automatically */
list_del_init(&old->mnt_expire);
out1:
- unlock_mount(path);
+ unlock_mount(mp);
out:
if (!err)
path_put(&parent_path);
@@ -1870,21 +1906,24 @@
*/
static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
{
+ struct mountpoint *mp;
+ struct mount *parent;
int err;
mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL);
- err = lock_mount(path);
- if (err)
- return err;
+ mp = lock_mount(path);
+ if (IS_ERR(mp))
+ return PTR_ERR(mp);
+ parent = real_mount(path->mnt);
err = -EINVAL;
- if (unlikely(!check_mnt(real_mount(path->mnt)))) {
+ if (unlikely(!check_mnt(parent))) {
/* that's acceptable only for automounts done in private ns */
if (!(mnt_flags & MNT_SHRINKABLE))
goto unlock;
/* ... and for those we'd better have mountpoint still alive */
- if (!real_mount(path->mnt)->mnt_ns)
+ if (!parent->mnt_ns)
goto unlock;
}
@@ -1899,10 +1938,10 @@
goto unlock;
newmnt->mnt.mnt_flags = mnt_flags;
- err = graft_tree(newmnt, path);
+ err = graft_tree(newmnt, parent, mp);
unlock:
- unlock_mount(path);
+ unlock_mount(mp);
return err;
}
@@ -2543,7 +2582,8 @@
const char __user *, put_old)
{
struct path new, old, parent_path, root_parent, root;
- struct mount *new_mnt, *root_mnt;
+ struct mount *new_mnt, *root_mnt, *old_mnt;
+ struct mountpoint *old_mp, *root_mp;
int error;
if (!may_mount())
@@ -2562,14 +2602,16 @@
goto out2;
get_fs_root(current->fs, &root);
- error = lock_mount(&old);
- if (error)
+ old_mp = lock_mount(&old);
+ error = PTR_ERR(old_mp);
+ if (IS_ERR(old_mp))
goto out3;
error = -EINVAL;
new_mnt = real_mount(new.mnt);
root_mnt = real_mount(root.mnt);
- if (IS_MNT_SHARED(real_mount(old.mnt)) ||
+ old_mnt = real_mount(old.mnt);
+ if (IS_MNT_SHARED(old_mnt) ||
IS_MNT_SHARED(new_mnt->mnt_parent) ||
IS_MNT_SHARED(root_mnt->mnt_parent))
goto out4;
@@ -2578,37 +2620,37 @@
error = -ENOENT;
if (d_unlinked(new.dentry))
goto out4;
- if (d_unlinked(old.dentry))
- goto out4;
error = -EBUSY;
- if (new.mnt == root.mnt ||
- old.mnt == root.mnt)
+ if (new_mnt == root_mnt || old_mnt == root_mnt)
goto out4; /* loop, on the same file system */
error = -EINVAL;
if (root.mnt->mnt_root != root.dentry)
goto out4; /* not a mountpoint */
if (!mnt_has_parent(root_mnt))
goto out4; /* not attached */
+ root_mp = root_mnt->mnt_mp;
if (new.mnt->mnt_root != new.dentry)
goto out4; /* not a mountpoint */
if (!mnt_has_parent(new_mnt))
goto out4; /* not attached */
/* make sure we can reach put_old from new_root */
- if (!is_path_reachable(real_mount(old.mnt), old.dentry, &new))
+ if (!is_path_reachable(old_mnt, old.dentry, &new))
goto out4;
+ root_mp->m_count++; /* pin it so it won't go away */
br_write_lock(&vfsmount_lock);
detach_mnt(new_mnt, &parent_path);
detach_mnt(root_mnt, &root_parent);
/* mount old root on put_old */
- attach_mnt(root_mnt, &old);
+ attach_mnt(root_mnt, old_mnt, old_mp);
/* mount new_root on / */
- attach_mnt(new_mnt, &root_parent);
+ attach_mnt(new_mnt, real_mount(root_parent.mnt), root_mp);
touch_mnt_namespace(current->nsproxy->mnt_ns);
br_write_unlock(&vfsmount_lock);
chroot_fs_refs(&root, &new);
+ put_mountpoint(root_mp);
error = 0;
out4:
- unlock_mount(&old);
+ unlock_mount(old_mp);
if (!error) {
path_put(&root_parent);
path_put(&parent_path);
@@ -2663,14 +2705,17 @@
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);
- if (!mount_hashtable)
+ 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]);
br_lock_init(&vfsmount_lock);
diff --git a/fs/pnode.c b/fs/pnode.c
index 3e000a5..98e0d3a 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -217,7 +217,7 @@
* @source_mnt: source mount.
* @tree_list : list of heads of trees to be attached.
*/
-int propagate_mnt(struct mount *dest_mnt, struct dentry *dest_dentry,
+int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp,
struct mount *source_mnt, struct list_head *tree_list)
{
struct mount *m, *child;
@@ -244,8 +244,8 @@
goto out;
}
- if (is_subdir(dest_dentry, m->mnt.mnt_root)) {
- mnt_set_mountpoint(m, dest_dentry, child);
+ 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);
} else {
/*
diff --git a/fs/pnode.h b/fs/pnode.h
index 19b853a3..f4357d3 100644
--- a/fs/pnode.h
+++ b/fs/pnode.h
@@ -31,14 +31,14 @@
}
void change_mnt_propagation(struct mount *, int);
-int propagate_mnt(struct mount *, struct dentry *, struct mount *,
+int propagate_mnt(struct mount *, struct mountpoint *, struct mount *,
struct list_head *);
int propagate_umount(struct list_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);
unsigned int mnt_get_count(struct mount *mnt);
-void mnt_set_mountpoint(struct mount *, struct dentry *,
+void mnt_set_mountpoint(struct mount *, struct mountpoint *,
struct mount *);
void release_mounts(struct list_head *);
void umount_tree(struct mount *, int, struct list_head *);
