Commit 84d17192 authored by Al Viro's avatar Al Viro
Browse files

get rid of full-hash scan on detaching vfsmounts


Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent e9c5d8a5
......@@ -18,6 +18,12 @@ struct mnt_pcp {
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 mount {
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;
......
......@@ -36,6 +36,7 @@ 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 kmem_cache *mnt_cache __read_mostly;
static struct rw_semaphore namespace_sem;
......@@ -605,6 +606,51 @@ 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 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;
......@@ -632,27 +678,6 @@ static void __touch_mnt_namespace(struct mnt_namespace *ns)
}
}
/*
* 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
*/
......@@ -664,32 +689,35 @@ static void detach_mnt(struct mount *mnt, struct path *old_path)
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 @@ void umount_tree(struct mount *mnt, int propagate, struct list_head *kill)
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 @@ static bool mnt_ns_loop(struct path *path)
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 @@ struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
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 @@ static int invent_group_ids(struct mount *mnt, bool recurse)
* 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 @@ static int attach_recursive_mnt(struct mount *source_mnt,
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 @@ static int attach_recursive_mnt(struct mount *source_mnt,
}
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 @@ static int attach_recursive_mnt(struct mount *source_mnt,
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 @@ static int do_loopback(struct path *path, const char *old_name,
{
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 @@ static int do_loopback(struct path *path, const char *old_name,
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 @@ static int do_loopback(struct path *path, const char *old_name,
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 @@ static int do_move_mount(struct path *path, const char *old_name)
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 @@ static int do_move_mount(struct path *path, const char *old_name)
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 @@ static int do_move_mount(struct path *path, const char *old_name)
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 @@ static int do_move_mount(struct path *path, const char *old_name)
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 @@ static int do_move_mount(struct path *path, const char *old_name)
* 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 struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
*/
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 @@ static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
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 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
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 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
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 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
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 @@ void __init mnt_init(void)
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);
......
......@@ -217,7 +217,7 @@ static struct mount *get_source(struct mount *dest,
* @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 @@ int propagate_mnt(struct mount *dest_mnt, struct dentry *dest_dentry,
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 {
/*
......
......@@ -31,14 +31,14 @@ static inline void set_mnt_shared(struct mount *mnt)
}
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 *);
......
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