3 files changed, 23 insertions, 4 deletions

diff --git a/fs/mount.h b/fs/mount.h
index b29e42f05f34..d55297f2fa05 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -10,7 +10,7 @@ struct mnt_namespace {
         struct user_namespace   *user_ns;
         u64                     seq;    /* Sequence number to prevent loops */
         wait_queue_head_t poll;
-        int event;
+        u64 event;
 };
 
 struct mnt_pcp {
@@ -104,6 +104,9 @@ struct proc_mounts {
         struct mnt_namespace *ns;
         struct path root;
         int (*show)(struct seq_file *, struct vfsmount *);
+        void *cached_mount;
+        u64 cached_event;
+        loff_t cached_index;
 };
 
 #define proc_mounts(p) (container_of((p), struct proc_mounts, m))
diff --git a/fs/namespace.c b/fs/namespace.c
index 65233a5f390a..a66aff5bd3fe 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -52,7 +52,7 @@ static int __init set_mphash_entries(char *str)
 }
 __setup("mphash_entries=", set_mphash_entries);
 
-static int event;
+static u64 event;
 static DEFINE_IDA(mnt_id_ida);
 static DEFINE_IDA(mnt_group_ida);
 static DEFINE_SPINLOCK(mnt_id_lock);
@@ -1100,14 +1100,29 @@ static void *m_start(struct seq_file *m, loff_t *pos)
         struct proc_mounts *p = proc_mounts(m);
 
         down_read(&namespace_sem);
-        return seq_list_start(&p->ns->list, *pos);
+        if (p->cached_event == p->ns->event) {
+                void *v = p->cached_mount;
+                if (*pos == p->cached_index)
+                        return v;
+                if (*pos == p->cached_index + 1) {
+                        v = seq_list_next(v, &p->ns->list, &p->cached_index);
+                        return p->cached_mount = v;
+                }
+        }
+
+        p->cached_event = p->ns->event;
+        p->cached_mount = seq_list_start(&p->ns->list, *pos);
+        p->cached_index = *pos;
+        return p->cached_mount;
 }
 
 static void *m_next(struct seq_file *m, void *v, loff_t *pos)
 {
         struct proc_mounts *p = proc_mounts(m);
 
-        return seq_list_next(v, &p->ns->list, pos);
+        p->cached_mount = seq_list_next(v, &p->ns->list, pos);
+        p->cached_index = *pos;
+        return p->cached_mount;
 }
 
 static void m_stop(struct seq_file *m, void *v)
diff --git a/fs/proc_namespace.c b/fs/proc_namespace.c
index 7be26f03a3f5..1a81373947f3 100644
--- a/fs/proc_namespace.c
+++ b/fs/proc_namespace.c
@@ -267,6 +267,7 @@ static int mounts_open_common(struct inode *inode, struct file *file,
         p->root = root;
         p->m.poll_event = ns->event;
         p->show = show;
+        p->cached_event = ~0ULL;
 
         return 0;