From 84d17192d2afd52aeba88c71ae4959a015f56a38 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Fri, 15 Mar 2013 10:53:28 -0400 Subject: [PATCH] get rid of full-hash scan on detaching vfsmounts Signed-off-by: Al Viro --- fs/mount.h | 7 ++ fs/namespace.c | 229 +++++++++++++++++++++++++++++-------------------- fs/pnode.c | 6 +- fs/pnode.h | 4 +- 4 files changed, 149 insertions(+), 97 deletions(-) diff --git a/fs/mount.h b/fs/mount.h index cd500798040..64a858143ff 100644 --- a/fs/mount.h +++ b/fs/mount.h @@ -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; diff --git a/fs/namespace.c b/fs/namespace.c index 6c7d31eebba..d7bb5a55cf3 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -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); diff --git a/fs/pnode.c b/fs/pnode.c index 3e000a51ac0..98e0d3a23fa 100644 --- a/fs/pnode.c +++ b/fs/pnode.c @@ -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 { /* diff --git a/fs/pnode.h b/fs/pnode.h index 19b853a3445..f4357d3a0a4 100644 --- a/fs/pnode.h +++ b/fs/pnode.h @@ -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 *); -- 2.20.1