From 56cbb429d911991170fe867b4bba14f0efed5829 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Thu, 4 Jul 2019 16:57:51 -0400 Subject: [PATCH] switch the remnants of releasing the mountpoint away from fs_pin We used to need rather convoluted ordering trickery to guarantee that dput() of ex-mountpoints happens before the final mntput() of the same. Since we don't need that anymore, there's no point playing with fs_pin for that. Signed-off-by: Al Viro --- fs/fs_pin.c | 14 ++++---------- fs/mount.h | 7 +++++-- fs/namespace.c | 37 +++++++++++++++++++------------------ include/linux/fs_pin.h | 1 - 4 files changed, 28 insertions(+), 31 deletions(-) diff --git a/fs/fs_pin.c b/fs/fs_pin.c index a6497cf8ae53..47ef3c71ce90 100644 --- a/fs/fs_pin.c +++ b/fs/fs_pin.c @@ -19,18 +19,12 @@ void pin_remove(struct fs_pin *pin) spin_unlock_irq(&pin->wait.lock); } -void pin_insert_group(struct fs_pin *pin, struct vfsmount *m, struct hlist_head *p) -{ - spin_lock(&pin_lock); - if (p) - hlist_add_head(&pin->s_list, p); - hlist_add_head(&pin->m_list, &real_mount(m)->mnt_pins); - spin_unlock(&pin_lock); -} - void pin_insert(struct fs_pin *pin, struct vfsmount *m) { - pin_insert_group(pin, m, &m->mnt_sb->s_pins); + spin_lock(&pin_lock); + hlist_add_head(&pin->s_list, &m->mnt_sb->s_pins); + hlist_add_head(&pin->m_list, &real_mount(m)->mnt_pins); + spin_unlock(&pin_lock); } void pin_kill(struct fs_pin *p) diff --git a/fs/mount.h b/fs/mount.h index 84aa8cdf4971..711a4093e475 100644 --- a/fs/mount.h +++ b/fs/mount.h @@ -58,7 +58,10 @@ struct mount { 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 */ - struct hlist_node mnt_mp_list; /* list mounts with the same mountpoint */ + union { + struct hlist_node mnt_mp_list; /* list mounts with the same mountpoint */ + struct hlist_node mnt_umount; + }; struct list_head mnt_umounting; /* list entry for umount propagation */ #ifdef CONFIG_FSNOTIFY struct fsnotify_mark_connector __rcu *mnt_fsnotify_marks; @@ -68,7 +71,7 @@ struct mount { int mnt_group_id; /* peer group identifier */ int mnt_expiry_mark; /* true if marked for expiry */ struct hlist_head mnt_pins; - struct fs_pin mnt_umount; + struct hlist_head mnt_stuck_children; } __randomize_layout; #define MNT_NS_INTERNAL ERR_PTR(-EINVAL) /* distinct from any mnt_namespace */ diff --git a/fs/namespace.c b/fs/namespace.c index 46316ba15615..54a815e48ead 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -171,13 +171,6 @@ unsigned int mnt_get_count(struct mount *mnt) #endif } -static void drop_mountpoint(struct fs_pin *p) -{ - struct mount *m = container_of(p, struct mount, mnt_umount); - pin_remove(p); - mntput(&m->mnt); -} - static struct mount *alloc_vfsmnt(const char *name) { struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); @@ -215,7 +208,7 @@ static struct mount *alloc_vfsmnt(const char *name) INIT_LIST_HEAD(&mnt->mnt_slave); INIT_HLIST_NODE(&mnt->mnt_mp_list); INIT_LIST_HEAD(&mnt->mnt_umounting); - init_fs_pin(&mnt->mnt_umount, drop_mountpoint); + INIT_HLIST_HEAD(&mnt->mnt_stuck_children); } return mnt; @@ -1087,19 +1080,22 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root, static void cleanup_mnt(struct mount *mnt) { + struct hlist_node *p; + struct mount *m; /* - * This probably indicates that somebody messed - * up a mnt_want/drop_write() pair. If this - * happens, the filesystem was probably unable - * to make r/w->r/o transitions. - */ - /* + * The warning here probably indicates that somebody messed + * up a mnt_want/drop_write() pair. If this happens, the + * filesystem was probably unable to make r/w->r/o transitions. * The locking used to deal with mnt_count decrement provides barriers, * so mnt_get_writers() below is safe. */ WARN_ON(mnt_get_writers(mnt)); if (unlikely(mnt->mnt_pins.first)) mnt_pin_kill(mnt); + hlist_for_each_entry_safe(m, p, &mnt->mnt_stuck_children, mnt_umount) { + hlist_del(&m->mnt_umount); + mntput(&m->mnt); + } fsnotify_vfsmount_delete(&mnt->mnt); dput(mnt->mnt.mnt_root); deactivate_super(mnt->mnt.mnt_sb); @@ -1168,6 +1164,7 @@ static void mntput_no_expire(struct mount *mnt) struct mount *p, *tmp; list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) { __put_mountpoint(unhash_mnt(p), &list); + hlist_add_head(&p->mnt_umount, &mnt->mnt_stuck_children); } } unlock_mount_hash(); @@ -1360,6 +1357,8 @@ EXPORT_SYMBOL(may_umount); static void namespace_unlock(void) { struct hlist_head head; + struct hlist_node *p; + struct mount *m; LIST_HEAD(list); hlist_move_list(&unmounted, &head); @@ -1374,7 +1373,10 @@ static void namespace_unlock(void) synchronize_rcu_expedited(); - group_pin_kill(&head); + hlist_for_each_entry_safe(m, p, &head, mnt_umount) { + hlist_del(&m->mnt_umount); + mntput(&m->mnt); + } } static inline void namespace_lock(void) @@ -1461,8 +1463,6 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how) disconnect = disconnect_mount(p, how); - pin_insert_group(&p->mnt_umount, &p->mnt_parent->mnt, - disconnect ? &unmounted : NULL); if (mnt_has_parent(p)) { mnt_add_count(p->mnt_parent, -1); if (!disconnect) { @@ -1470,6 +1470,7 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how) list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts); } else { umount_mnt(p); + hlist_add_head(&p->mnt_umount, &unmounted); } } change_mnt_propagation(p, MS_PRIVATE); @@ -1622,8 +1623,8 @@ void __detach_mounts(struct dentry *dentry) while (!hlist_empty(&mp->m_list)) { mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list); if (mnt->mnt.mnt_flags & MNT_UMOUNT) { - hlist_add_head(&mnt->mnt_umount.s_list, &unmounted); umount_mnt(mnt); + hlist_add_head(&mnt->mnt_umount, &unmounted); } else umount_tree(mnt, UMOUNT_CONNECTED); } diff --git a/include/linux/fs_pin.h b/include/linux/fs_pin.h index 7cab74d66f85..bdd09fd2520c 100644 --- a/include/linux/fs_pin.h +++ b/include/linux/fs_pin.h @@ -20,6 +20,5 @@ static inline void init_fs_pin(struct fs_pin *p, void (*kill)(struct fs_pin *)) } void pin_remove(struct fs_pin *); -void pin_insert_group(struct fs_pin *, struct vfsmount *, struct hlist_head *); void pin_insert(struct fs_pin *, struct vfsmount *); void pin_kill(struct fs_pin *);