switch the IO-triggering parts of umount to fs_pin

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

3 files changed, 20 insertions, 29 deletions

diff --git a/fs/fs_pin.c b/fs/fs_pin.c
index 0c77bdc238b2..b06c98796afb 100644
--- a/fs/fs_pin.c
+++ b/fs/fs_pin.c
@@ -1,7 +1,6 @@
 #include <linux/fs.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
-#include <linux/fs_pin.h>
 #include "internal.h"
 #include "mount.h"
 
diff --git a/fs/mount.h b/fs/mount.h
index 0ad6f760ce52..6a61c2b3e385 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -2,6 +2,7 @@
 #include <linux/seq_file.h>
 #include <linux/poll.h>
 #include <linux/ns_common.h>
+#include <linux/fs_pin.h>
 
 struct mnt_namespace {
         atomic_t                count;
@@ -62,7 +63,8 @@ struct mount {
         int mnt_group_id;               /* peer group identifier */
         int mnt_expiry_mark;            /* true if marked for expiry */
         struct hlist_head mnt_pins;
-        struct path mnt_ex_mountpoint;
+        struct fs_pin mnt_umount;
+        struct dentry *mnt_ex_mountpoint;
 };
 
 #define MNT_NS_INTERNAL ERR_PTR(-EINVAL) /* distinct from any mnt_namespace */
diff --git a/fs/namespace.c b/fs/namespace.c
index cd1e9681a0cf..4a985ff0ddfc 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -190,6 +190,14 @@ 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);
+        dput(m->mnt_ex_mountpoint);
+        pin_remove(p);
+        mntput(&m->mnt);
+}
+
 static struct mount *alloc_vfsmnt(const char *name)
 {
         struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
@@ -229,6 +237,7 @@ static struct mount *alloc_vfsmnt(const char *name)
 #ifdef CONFIG_FSNOTIFY
                 INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks);
 #endif
+                init_fs_pin(&mnt->mnt_umount, drop_mountpoint);
         }
         return mnt;
 
@@ -1289,7 +1298,6 @@ static HLIST_HEAD(unmounted);	/* protected by namespace_sem */
 
 static void namespace_unlock(void)
 {
-        struct mount *mnt;
         struct hlist_head head = unmounted;
 
         if (likely(hlist_empty(&head))) {
@@ -1299,23 +1307,11 @@ static void namespace_unlock(void)
 
         head.first->pprev = &head.first;
         INIT_HLIST_HEAD(&unmounted);
-
-        /* undo decrements we'd done in umount_tree() */
-        hlist_for_each_entry(mnt, &head, mnt_hash)
-                if (mnt->mnt_ex_mountpoint.mnt)
-                        mntget(mnt->mnt_ex_mountpoint.mnt);
-
         up_write(&namespace_sem);
 
         synchronize_rcu();
 
-        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);
-        }
+        group_pin_kill(&head);
 }
 
 static inline void namespace_lock(void)
@@ -1334,7 +1330,6 @@ void umount_tree(struct mount *mnt, int how)
 {
         HLIST_HEAD(tmp_list);
         struct mount *p;
-        struct mount *last = NULL;
 
         for (p = mnt; p; p = next_mnt(p, mnt)) {
                 hlist_del_init_rcu(&p->mnt_hash);
@@ -1347,33 +1342,28 @@ void umount_tree(struct mount *mnt, int how)
         if (how)
                 propagate_umount(&tmp_list);
 
-        hlist_for_each_entry(p, &tmp_list, mnt_hash) {
+        while (!hlist_empty(&tmp_list)) {
+                p = hlist_entry(tmp_list.first, struct mount, mnt_hash);
+                hlist_del_init_rcu(&p->mnt_hash);
                 list_del_init(&p->mnt_expire);
                 list_del_init(&p->mnt_list);
                 __touch_mnt_namespace(p->mnt_ns);
                 p->mnt_ns = NULL;
                 if (how < 2)
                         p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
+
+                pin_insert_group(&p->mnt_umount, &p->mnt_parent->mnt, &unmounted);
                 if (mnt_has_parent(p)) {
                         hlist_del_init(&p->mnt_mp_list);
                         put_mountpoint(p->mnt_mp);
                         mnt_add_count(p->mnt_parent, -1);
-                        /* move the reference to mountpoint into ->mnt_ex_mountpoint */
-                        p->mnt_ex_mountpoint.dentry = p->mnt_mountpoint;
-                        p->mnt_ex_mountpoint.mnt = &p->mnt_parent->mnt;
+                        /* old mountpoint will be dropped when we can do that */
+                        p->mnt_ex_mountpoint = p->mnt_mountpoint;
                         p->mnt_mountpoint = p->mnt.mnt_root;
                         p->mnt_parent = p;
                         p->mnt_mp = NULL;
                 }
                 change_mnt_propagation(p, MS_PRIVATE);
-                last = p;
-        }
-        if (last) {
-                last->mnt_hash.next = unmounted.first;
-                if (unmounted.first)
-                        unmounted.first->pprev = &last->mnt_hash.next;
-                unmounted.first = tmp_list.first;
-                unmounted.first->pprev = &unmounted.first;
         }
 }