12 files changed, 573 insertions, 138 deletions

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 518ebe609e2b..2a99116edc47 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -43,6 +43,7 @@ Table of Contents
   2.13  /proc/<pid>/oom_score - Display current oom-killer score
   2.14  /proc/<pid>/io - Display the IO accounting fields
   2.15  /proc/<pid>/coredump_filter - Core dump filtering settings
+  2.16  /proc/<pid>/mountinfo - Information about mounts
 
 ------------------------------------------------------------------------------
 Preface
@@ -2348,4 +2349,41 @@ For example:
   $ echo 0x7 > /proc/self/coredump_filter
   $ ./some_program
 
+2.16    /proc/<pid>/mountinfo - Information about mounts
+--------------------------------------------------------
+
+This file contains lines of the form:
+
+36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
+(1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)
+
+(1) mount ID:  unique identifier of the mount (may be reused after umount)
+(2) parent ID:  ID of parent (or of self for the top of the mount tree)
+(3) major:minor:  value of st_dev for files on filesystem
+(4) root:  root of the mount within the filesystem
+(5) mount point:  mount point relative to the process's root
+(6) mount options:  per mount options
+(7) optional fields:  zero or more fields of the form "tag[:value]"
+(8) separator:  marks the end of the optional fields
+(9) filesystem type:  name of filesystem of the form "type[.subtype]"
+(10) mount source:  filesystem specific information or "none"
+(11) super options:  per super block options
+
+Parsers should ignore all unrecognised optional fields.  Currently the
+possible optional fields are:
+
+shared:X  mount is shared in peer group X
+master:X  mount is slave to peer group X
+propagate_from:X  mount is slave and receives propagation from peer group X (*)
+unbindable  mount is unbindable
+
+(*) X is the closest dominant peer group under the process's root.  If
+X is the immediate master of the mount, or if there's no dominant peer
+group under the same root, then only the "master:X" field is present
+and not the "propagate_from:X" field.
+
+For more information on mount propagation see:
+
+  Documentation/filesystems/sharedsubtree.txt
+
 ------------------------------------------------------------------------------
diff --git a/fs/dcache.c b/fs/dcache.c
index 43455776711e..3ee588d5f585 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1746,12 +1746,21 @@ shouldnt_be_hashed:
         goto shouldnt_be_hashed;
 }
 
+static int prepend(char **buffer, int *buflen, const char *str,
+                          int namelen)
+{
+        *buflen -= namelen;
+        if (*buflen < 0)
+                return -ENAMETOOLONG;
+        *buffer -= namelen;
+        memcpy(*buffer, str, namelen);
+        return 0;
+}
+
 /**
  * d_path - return the path of a dentry
- * @dentry: dentry to report
- * @vfsmnt: vfsmnt to which the dentry belongs
- * @root: root dentry
- * @rootmnt: vfsmnt to which the root dentry belongs
+ * @path: the dentry/vfsmount to report
+ * @root: root vfsmnt/dentry (may be modified by this function)
  * @buffer: buffer to return value in
  * @buflen: buffer length
  *
@@ -1761,23 +1770,22 @@ shouldnt_be_hashed:
  * Returns the buffer or an error code if the path was too long.
  *
  * "buflen" should be positive. Caller holds the dcache_lock.
+ *
+ * If path is not reachable from the supplied root, then the value of
+ * root is changed (without modifying refcounts).
  */
-static char *__d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
-                       struct path *root, char *buffer, int buflen)
+char *__d_path(const struct path *path, struct path *root,
+               char *buffer, int buflen)
 {
+        struct dentry *dentry = path->dentry;
+        struct vfsmount *vfsmnt = path->mnt;
         char * end = buffer+buflen;
         char * retval;
-        int namelen;
-
-        *--end = '\0';
-        buflen--;
-        if (!IS_ROOT(dentry) && d_unhashed(dentry)) {
-                buflen -= 10;
-                end -= 10;
-                if (buflen < 0)
+
+        prepend(&end, &buflen, "\0", 1);
+        if (!IS_ROOT(dentry) && d_unhashed(dentry) &&
+                (prepend(&end, &buflen, " (deleted)", 10) != 0))
                         goto Elong;
-                memcpy(end, " (deleted)", 10);
-        }
 
         if (buflen < 1)
                 goto Elong;
@@ -1804,13 +1812,10 @@ static char *__d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
                 }
                 parent = dentry->d_parent;
                 prefetch(parent);
-                namelen = dentry->d_name.len;
-                buflen -= namelen + 1;
-                if (buflen < 0)
+                if ((prepend(&end, &buflen, dentry->d_name.name,
+                                dentry->d_name.len) != 0) ||
+                    (prepend(&end, &buflen, "/", 1) != 0))
                         goto Elong;
-                end -= namelen;
-                memcpy(end, dentry->d_name.name, namelen);
-                *--end = '/';
                 retval = end;
                 dentry = parent;
         }
@@ -1818,12 +1823,12 @@ static char *__d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
         return retval;
 
 global_root:
-        namelen = dentry->d_name.len;
-        buflen -= namelen;
-        if (buflen < 0)
+        retval += 1;    /* hit the slash */
+        if (prepend(&retval, &buflen, dentry->d_name.name,
+                    dentry->d_name.len) != 0)
                 goto Elong;
-        retval -= namelen-1;    /* hit the slash */
-        memcpy(retval, dentry->d_name.name, namelen);
+        root->mnt = vfsmnt;
+        root->dentry = dentry;
         return retval;
 Elong:
         return ERR_PTR(-ENAMETOOLONG);
@@ -1846,6 +1851,7 @@ char *d_path(struct path *path, char *buf, int buflen)
 {
         char *res;
         struct path root;
+        struct path tmp;
 
         /*
          * We have various synthetic filesystems that never get mounted.  On
@@ -1859,10 +1865,11 @@ char *d_path(struct path *path, char *buf, int buflen)
 
         read_lock(&current->fs->lock);
         root = current->fs->root;
-        path_get(&current->fs->root);
+        path_get(&root);
         read_unlock(&current->fs->lock);
         spin_lock(&dcache_lock);
-        res = __d_path(path->dentry, path->mnt, &root, buf, buflen);
+        tmp = root;
+        res = __d_path(path, &tmp, buf, buflen);
         spin_unlock(&dcache_lock);
         path_put(&root);
         return res;
@@ -1890,6 +1897,48 @@ char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
 }
 
 /*
+ * Write full pathname from the root of the filesystem into the buffer.
+ */
+char *dentry_path(struct dentry *dentry, char *buf, int buflen)
+{
+        char *end = buf + buflen;
+        char *retval;
+
+        spin_lock(&dcache_lock);
+        prepend(&end, &buflen, "\0", 1);
+        if (!IS_ROOT(dentry) && d_unhashed(dentry) &&
+                (prepend(&end, &buflen, "//deleted", 9) != 0))
+                        goto Elong;
+        if (buflen < 1)
+                goto Elong;
+        /* Get '/' right */
+        retval = end-1;
+        *retval = '/';
+
+        for (;;) {
+                struct dentry *parent;
+                if (IS_ROOT(dentry))
+                        break;
+
+                parent = dentry->d_parent;
+                prefetch(parent);
+
+                if ((prepend(&end, &buflen, dentry->d_name.name,
+                                dentry->d_name.len) != 0) ||
+                    (prepend(&end, &buflen, "/", 1) != 0))
+                        goto Elong;
+
+                retval = end;
+                dentry = parent;
+        }
+        spin_unlock(&dcache_lock);
+        return retval;
+Elong:
+        spin_unlock(&dcache_lock);
+        return ERR_PTR(-ENAMETOOLONG);
+}
+
+/*
  * NOTE! The user-level library version returns a
  * character pointer. The kernel system call just
  * returns the length of the buffer filled (which
@@ -1918,9 +1967,9 @@ asmlinkage long sys_getcwd(char __user *buf, unsigned long size)
 
         read_lock(&current->fs->lock);
         pwd = current->fs->pwd;
-        path_get(&current->fs->pwd);
+        path_get(&pwd);
         root = current->fs->root;
-        path_get(&current->fs->root);
+        path_get(&root);
         read_unlock(&current->fs->lock);
 
         error = -ENOENT;
@@ -1928,9 +1977,10 @@ asmlinkage long sys_getcwd(char __user *buf, unsigned long size)
         spin_lock(&dcache_lock);
         if (pwd.dentry->d_parent == pwd.dentry || !d_unhashed(pwd.dentry)) {
                 unsigned long len;
+                struct path tmp = root;
                 char * cwd;
 
-                cwd = __d_path(pwd.dentry, pwd.mnt, &root, page, PAGE_SIZE);
+                cwd = __d_path(&pwd, &tmp, page, PAGE_SIZE);
                 spin_unlock(&dcache_lock);
 
                 error = PTR_ERR(cwd);
diff --git a/fs/namespace.c b/fs/namespace.c
index 1bf302d0478b..0505fb61aa74 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -27,6 +27,7 @@
 #include <linux/mount.h>
 #include <linux/ramfs.h>
 #include <linux/log2.h>
+#include <linux/idr.h>
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
 #include "pnode.h"
@@ -39,6 +40,8 @@
 __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock);
 
 static int event;
+static DEFINE_IDA(mnt_id_ida);
+static DEFINE_IDA(mnt_group_ida);
 
 static struct list_head *mount_hashtable __read_mostly;
 static struct kmem_cache *mnt_cache __read_mostly;
@@ -58,10 +61,63 @@ static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
 
 #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16)
 
+/* allocation is serialized by namespace_sem */
+static int mnt_alloc_id(struct vfsmount *mnt)
+{
+        int res;
+
+retry:
+        ida_pre_get(&mnt_id_ida, GFP_KERNEL);
+        spin_lock(&vfsmount_lock);
+        res = ida_get_new(&mnt_id_ida, &mnt->mnt_id);
+        spin_unlock(&vfsmount_lock);
+        if (res == -EAGAIN)
+                goto retry;
+
+        return res;
+}
+
+static void mnt_free_id(struct vfsmount *mnt)
+{
+        spin_lock(&vfsmount_lock);
+        ida_remove(&mnt_id_ida, mnt->mnt_id);
+        spin_unlock(&vfsmount_lock);
+}
+
+/*
+ * Allocate a new peer group ID
+ *
+ * mnt_group_ida is protected by namespace_sem
+ */
+static int mnt_alloc_group_id(struct vfsmount *mnt)
+{
+        if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
+                return -ENOMEM;
+
+        return ida_get_new_above(&mnt_group_ida, 1, &mnt->mnt_group_id);
+}
+
+/*
+ * Release a peer group ID
+ */
+void mnt_release_group_id(struct vfsmount *mnt)
+{
+        ida_remove(&mnt_group_ida, mnt->mnt_group_id);
+        mnt->mnt_group_id = 0;
+}
+
 struct vfsmount *alloc_vfsmnt(const char *name)
 {
         struct vfsmount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
         if (mnt) {
+                int err;
+
+                err = mnt_alloc_id(mnt);
+                if (err) {
+                        kmem_cache_free(mnt_cache, mnt);
+                        return NULL;
+                }
+
                 atomic_set(&mnt->mnt_count, 1);
                 INIT_LIST_HEAD(&mnt->mnt_hash);
                 INIT_LIST_HEAD(&mnt->mnt_child);
@@ -353,6 +409,7 @@ EXPORT_SYMBOL(simple_set_mnt);
 void free_vfsmnt(struct vfsmount *mnt)
 {
         kfree(mnt->mnt_devname);
+        mnt_free_id(mnt);
         kmem_cache_free(mnt_cache, mnt);
 }
 
@@ -499,6 +556,17 @@ static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
         struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname);
 
         if (mnt) {
+                if (flag & (CL_SLAVE | CL_PRIVATE))
+                        mnt->mnt_group_id = 0; /* not a peer of original */
+                else
+                        mnt->mnt_group_id = old->mnt_group_id;
+
+                if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
+                        int err = mnt_alloc_group_id(mnt);
+                        if (err)
+                                goto out_free;
+                }
+
                 mnt->mnt_flags = old->mnt_flags;
                 atomic_inc(&sb->s_active);
                 mnt->mnt_sb = sb;
@@ -528,6 +596,10 @@ static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
                 }
         }
         return mnt;
+
+ out_free:
+        free_vfsmnt(mnt);
+        return NULL;
 }
 
 static inline void __mntput(struct vfsmount *mnt)
@@ -652,20 +724,21 @@ void save_mount_options(struct super_block *sb, char *options)
 }
 EXPORT_SYMBOL(save_mount_options);
 
+#ifdef CONFIG_PROC_FS
 /* iterator */
 static void *m_start(struct seq_file *m, loff_t *pos)
 {
-        struct mnt_namespace *n = m->private;
+        struct proc_mounts *p = m->private;
 
         down_read(&namespace_sem);
-        return seq_list_start(&n->list, *pos);
+        return seq_list_start(&p->ns->list, *pos);
 }
 
 static void *m_next(struct seq_file *m, void *v, loff_t *pos)
 {
-        struct mnt_namespace *n = m->private;
+        struct proc_mounts *p = m->private;
 
-        return seq_list_next(v, &n->list, pos);
+        return seq_list_next(v, &p->ns->list, pos);
 }
 
 static void m_stop(struct seq_file *m, void *v)
@@ -673,20 +746,30 @@ static void m_stop(struct seq_file *m, void *v)
         up_read(&namespace_sem);
 }
 
-static int show_vfsmnt(struct seq_file *m, void *v)
+struct proc_fs_info {
+        int flag;
+        const char *str;
+};
+
+static void show_sb_opts(struct seq_file *m, struct super_block *sb)
 {
-        struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
-        int err = 0;
-        static struct proc_fs_info {
-                int flag;
-                char *str;
-        } fs_info[] = {
+        static const struct proc_fs_info fs_info[] = {
                 { MS_SYNCHRONOUS, ",sync" },
                 { MS_DIRSYNC, ",dirsync" },
                 { MS_MANDLOCK, ",mand" },
                 { 0, NULL }
         };
-        static struct proc_fs_info mnt_info[] = {
+        const struct proc_fs_info *fs_infop;
+
+        for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
+                if (sb->s_flags & fs_infop->flag)
+                        seq_puts(m, fs_infop->str);
+        }
+}
+
+static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt)
+{
+        static const struct proc_fs_info mnt_info[] = {
                 { MNT_NOSUID, ",nosuid" },
                 { MNT_NODEV, ",nodev" },
                 { MNT_NOEXEC, ",noexec" },
@@ -695,40 +778,108 @@ static int show_vfsmnt(struct seq_file *m, void *v)
                 { MNT_RELATIME, ",relatime" },
                 { 0, NULL }
         };
-        struct proc_fs_info *fs_infop;
+        const struct proc_fs_info *fs_infop;
+
+        for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
+                if (mnt->mnt_flags & fs_infop->flag)
+                        seq_puts(m, fs_infop->str);
+        }
+}
+
+static void show_type(struct seq_file *m, struct super_block *sb)
+{
+        mangle(m, sb->s_type->name);
+        if (sb->s_subtype && sb->s_subtype[0]) {
+                seq_putc(m, '.');
+                mangle(m, sb->s_subtype);
+        }
+}
+
+static int show_vfsmnt(struct seq_file *m, void *v)
+{
+        struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
+        int err = 0;
         struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
 
         mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
         seq_putc(m, ' ');
         seq_path(m, &mnt_path, " \t\n\\");
         seq_putc(m, ' ');
-        mangle(m, mnt->mnt_sb->s_type->name);
-        if (mnt->mnt_sb->s_subtype && mnt->mnt_sb->s_subtype[0]) {
-                seq_putc(m, '.');
-                mangle(m, mnt->mnt_sb->s_subtype);
-        }
+        show_type(m, mnt->mnt_sb);
         seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");
-        for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
-                if (mnt->mnt_sb->s_flags & fs_infop->flag)
-                        seq_puts(m, fs_infop->str);
-        }
-        for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
-                if (mnt->mnt_flags & fs_infop->flag)
-                        seq_puts(m, fs_infop->str);
-        }
+        show_sb_opts(m, mnt->mnt_sb);
+        show_mnt_opts(m, mnt);
         if (mnt->mnt_sb->s_op->show_options)
                 err = mnt->mnt_sb->s_op->show_options(m, mnt);
         seq_puts(m, " 0 0\n");
         return err;
 }
 
-struct seq_operations mounts_op = {
+const struct seq_operations mounts_op = {
         .start  = m_start,
         .next   = m_next,
         .stop   = m_stop,
         .show   = show_vfsmnt
 };
 
+static int show_mountinfo(struct seq_file *m, void *v)
+{
+        struct proc_mounts *p = m->private;
+        struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
+        struct super_block *sb = mnt->mnt_sb;
+        struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
+        struct path root = p->root;
+        int err = 0;
+
+        seq_printf(m, "%i %i %u:%u ", mnt->mnt_id, mnt->mnt_parent->mnt_id,
+                   MAJOR(sb->s_dev), MINOR(sb->s_dev));
+        seq_dentry(m, mnt->mnt_root, " \t\n\\");
+        seq_putc(m, ' ');
+        seq_path_root(m, &mnt_path, &root, " \t\n\\");
+        if (root.mnt != p->root.mnt || root.dentry != p->root.dentry) {
+                /*
+                 * Mountpoint is outside root, discard that one.  Ugly,
+                 * but less so than trying to do that in iterator in a
+                 * race-free way (due to renames).
+                 */
+                return SEQ_SKIP;
+        }
+        seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw");
+        show_mnt_opts(m, mnt);
+
+        /* Tagged fields ("foo:X" or "bar") */
+        if (IS_MNT_SHARED(mnt))
+                seq_printf(m, " shared:%i", mnt->mnt_group_id);
+        if (IS_MNT_SLAVE(mnt)) {
+                int master = mnt->mnt_master->mnt_group_id;
+                int dom = get_dominating_id(mnt, &p->root);
+                seq_printf(m, " master:%i", master);
+                if (dom && dom != master)
+                        seq_printf(m, " propagate_from:%i", dom);
+        }
+        if (IS_MNT_UNBINDABLE(mnt))
+                seq_puts(m, " unbindable");
+
+        /* Filesystem specific data */
+        seq_puts(m, " - ");
+        show_type(m, sb);
+        seq_putc(m, ' ');
+        mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
+        seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw");
+        show_sb_opts(m, sb);
+        if (sb->s_op->show_options)
+                err = sb->s_op->show_options(m, mnt);
+        seq_putc(m, '\n');
+        return err;
+}
+
+const struct seq_operations mountinfo_op = {
+        .start  = m_start,
+        .next   = m_next,
+        .stop   = m_stop,
+        .show   = show_mountinfo,
+};
+
 static int show_vfsstat(struct seq_file *m, void *v)
 {
         struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
@@ -749,7 +900,7 @@ static int show_vfsstat(struct seq_file *m, void *v)
 
         /* file system type */
         seq_puts(m, "with fstype ");
-        mangle(m, mnt->mnt_sb->s_type->name);
+        show_type(m, mnt->mnt_sb);
 
         /* optional statistics */
         if (mnt->mnt_sb->s_op->show_stats) {
@@ -761,12 +912,13 @@ static int show_vfsstat(struct seq_file *m, void *v)
         return err;
 }
 
-struct seq_operations mountstats_op = {
+const struct seq_operations mountstats_op = {
         .start  = m_start,
         .next   = m_next,
         .stop   = m_stop,
         .show   = show_vfsstat,
 };
+#endif  /* CONFIG_PROC_FS */
 
 /**
  * may_umount_tree - check if a mount tree is busy
@@ -1108,6 +1260,33 @@ void drop_collected_mounts(struct vfsmount *mnt)
         release_mounts(&umount_list);
 }
 
+static void cleanup_group_ids(struct vfsmount *mnt, struct vfsmount *end)
+{
+        struct vfsmount *p;
+
+        for (p = mnt; p != end; p = next_mnt(p, mnt)) {
+                if (p->mnt_group_id && !IS_MNT_SHARED(p))
+                        mnt_release_group_id(p);
+        }
+}
+
+static int invent_group_ids(struct vfsmount *mnt, bool recurse)
+{
+        struct vfsmount *p;
+
+        for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
+                if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
+                        int err = mnt_alloc_group_id(p);
+                        if (err) {
+                                cleanup_group_ids(mnt, p);
+                                return err;
+                        }
+                }
+        }
+
+        return 0;
+}
+
 /*
  *  @source_mnt : mount tree to be attached
  *  @nd         : place the mount tree @source_mnt is attached
@@ -1178,9 +1357,16 @@ static int attach_recursive_mnt(struct vfsmount *source_mnt,
         struct vfsmount *dest_mnt = path->mnt;
         struct dentry *dest_dentry = path->dentry;
         struct vfsmount *child, *p;
+        int err;
 
-        if (propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list))
-                return -EINVAL;
+        if (IS_MNT_SHARED(dest_mnt)) {
+                err = invent_group_ids(source_mnt, true);
+                if (err)
+                        goto out;
+        }
+        err = propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list);
+        if (err)
+                goto out_cleanup_ids;
 
         if (IS_MNT_SHARED(dest_mnt)) {
                 for (p = source_mnt; p; p = next_mnt(p, source_mnt))
@@ -1203,6 +1389,12 @@ static int attach_recursive_mnt(struct vfsmount *source_mnt,
         }
         spin_unlock(&vfsmount_lock);
         return 0;
+
+ out_cleanup_ids:
+        if (IS_MNT_SHARED(dest_mnt))
+                cleanup_group_ids(source_mnt, NULL);
+ out:
+        return err;
 }
 
 static int graft_tree(struct vfsmount *mnt, struct path *path)
@@ -1243,6 +1435,7 @@ static noinline int do_change_type(struct nameidata *nd, int flag)
         struct vfsmount *m, *mnt = nd->path.mnt;
         int recurse = flag & MS_REC;
         int type = flag & ~MS_REC;
+        int err = 0;
 
         if (!capable(CAP_SYS_ADMIN))
                 return -EPERM;
@@ -1251,12 +1444,20 @@ static noinline int do_change_type(struct nameidata *nd, int flag)
                 return -EINVAL;
 
         down_write(&namespace_sem);
+        if (type == MS_SHARED) {
+                err = invent_group_ids(mnt, recurse);
+                if (err)
+                        goto out_unlock;
+        }
+
         spin_lock(&vfsmount_lock);
         for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
                 change_mnt_propagation(m, type);
         spin_unlock(&vfsmount_lock);
+
+ out_unlock:
         up_write(&namespace_sem);
-        return 0;
+        return err;
 }
 
 /*
diff --git a/fs/pnode.c b/fs/pnode.c
index f968e35d9785..8d5f392ec3d3 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -28,6 +28,57 @@ static inline struct vfsmount *next_slave(struct vfsmount *p)
         return list_entry(p->mnt_slave.next, struct vfsmount, mnt_slave);
 }
 
+/*
+ * Return true if path is reachable from root
+ *
+ * namespace_sem is held, and mnt is attached
+ */
+static bool is_path_reachable(struct vfsmount *mnt, struct dentry *dentry,
+                         const struct path *root)
+{
+        while (mnt != root->mnt && mnt->mnt_parent != mnt) {
+                dentry = mnt->mnt_mountpoint;
+                mnt = mnt->mnt_parent;
+        }
+        return mnt == root->mnt && is_subdir(dentry, root->dentry);
+}
+
+static struct vfsmount *get_peer_under_root(struct vfsmount *mnt,
+                                            struct mnt_namespace *ns,
+                                            const struct path *root)
+{
+        struct vfsmount *m = mnt;
+
+        do {
+                /* Check the namespace first for optimization */
+                if (m->mnt_ns == ns && is_path_reachable(m, m->mnt_root, root))
+                        return m;
+
+                m = next_peer(m);
+        } while (m != mnt);
+
+        return NULL;
+}
+
+/*
+ * Get ID of closest dominating peer group having a representative
+ * under the given root.
+ *
+ * Caller must hold namespace_sem
+ */
+int get_dominating_id(struct vfsmount *mnt, const struct path *root)
+{
+        struct vfsmount *m;
+
+        for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) {
+                struct vfsmount *d = get_peer_under_root(m, mnt->mnt_ns, root);
+                if (d)
+                        return d->mnt_group_id;
+        }
+
+        return 0;
+}
+
 static int do_make_slave(struct vfsmount *mnt)
 {
         struct vfsmount *peer_mnt = mnt, *master = mnt->mnt_master;
@@ -46,7 +97,11 @@ static int do_make_slave(struct vfsmount *mnt)
                 if (peer_mnt == mnt)
                         peer_mnt = NULL;
         }
+        if (IS_MNT_SHARED(mnt) && list_empty(&mnt->mnt_share))
+                mnt_release_group_id(mnt);
+
         list_del_init(&mnt->mnt_share);
+        mnt->mnt_group_id = 0;
 
         if (peer_mnt)
                 master = peer_mnt;
@@ -68,7 +123,6 @@ static int do_make_slave(struct vfsmount *mnt)
         }
         mnt->mnt_master = master;
         CLEAR_MNT_SHARED(mnt);
-        INIT_LIST_HEAD(&mnt->mnt_slave_list);
         return 0;
 }
 
diff --git a/fs/pnode.h b/fs/pnode.h
index 973c3f825e7d..958665d662af 100644
--- a/fs/pnode.h
+++ b/fs/pnode.h
@@ -36,4 +36,5 @@ int propagate_mnt(struct vfsmount *, struct dentry *, struct vfsmount *,
 int propagate_umount(struct list_head *);
 int propagate_mount_busy(struct vfsmount *, int);
 void mnt_release_group_id(struct vfsmount *);
+int get_dominating_id(struct vfsmount *mnt, const struct path *root);
 #endif /* _LINUX_PNODE_H */
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 7313c62e3e9d..c5e412a00b17 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -502,17 +502,14 @@ static const struct inode_operations proc_def_inode_operations = {
         .setattr        = proc_setattr,
 };
 
-extern const struct seq_operations mounts_op;
-struct proc_mounts {
-        struct seq_file m;
-        int event;
-};
-
-static int mounts_open(struct inode *inode, struct file *file)
+static int mounts_open_common(struct inode *inode, struct file *file,
+                              const struct seq_operations *op)
 {
         struct task_struct *task = get_proc_task(inode);
         struct nsproxy *nsp;
         struct mnt_namespace *ns = NULL;
+        struct fs_struct *fs = NULL;
+        struct path root;
         struct proc_mounts *p;
         int ret = -EINVAL;
 
@@ -525,40 +522,61 @@ static int mounts_open(struct inode *inode, struct file *file)
                                 get_mnt_ns(ns);
                 }
                 rcu_read_unlock();
-
+                if (ns)
+                        fs = get_fs_struct(task);
                 put_task_struct(task);
         }
 
-        if (ns) {
-                ret = -ENOMEM;
-                p = kmalloc(sizeof(struct proc_mounts), GFP_KERNEL);
-                if (p) {
-                        file->private_data = &p->m;
-                        ret = seq_open(file, &mounts_op);
-                        if (!ret) {
-                                p->m.private = ns;
-                                p->event = ns->event;
-                                return 0;
-                        }
-                        kfree(p);
-                }
-                put_mnt_ns(ns);
-        }
+        if (!ns)
+                goto err;
+        if (!fs)
+                goto err_put_ns;
+
+        read_lock(&fs->lock);
+        root = fs->root;
+        path_get(&root);
+        read_unlock(&fs->lock);
+        put_fs_struct(fs);
+
+        ret = -ENOMEM;
+        p = kmalloc(sizeof(struct proc_mounts), GFP_KERNEL);
+        if (!p)
+                goto err_put_path;
+
+        file->private_data = &p->m;
+        ret = seq_open(file, op);
+        if (ret)
+                goto err_free;
+
+        p->m.private = p;
+        p->ns = ns;
+        p->root = root;
+        p->event = ns->event;
+
+        return 0;
+
+ err_free:
+        kfree(p);
+ err_put_path:
+        path_put(&root);
+ err_put_ns:
+        put_mnt_ns(ns);
+ err:
         return ret;
 }
 
 static int mounts_release(struct inode *inode, struct file *file)
 {
-        struct seq_file *m = file->private_data;
-        struct mnt_namespace *ns = m->private;
-        put_mnt_ns(ns);
+        struct proc_mounts *p = file->private_data;
+        path_put(&p->root);
+        put_mnt_ns(p->ns);
         return seq_release(inode, file);
 }
 
 static unsigned mounts_poll(struct file *file, poll_table *wait)
 {
         struct proc_mounts *p = file->private_data;
-        struct mnt_namespace *ns = p->m.private;
+        struct mnt_namespace *ns = p->ns;
         unsigned res = 0;
 
         poll_wait(file, &ns->poll, wait);
@@ -573,6 +591,11 @@ static unsigned mounts_poll(struct file *file, poll_table *wait)
         return res;
 }
 
+static int mounts_open(struct inode *inode, struct file *file)
+{
+        return mounts_open_common(inode, file, &mounts_op);
+}
+
 static const struct file_operations proc_mounts_operations = {
         .open           = mounts_open,
         .read           = seq_read,
@@ -581,38 +604,22 @@ static const struct file_operations proc_mounts_operations = {
         .poll           = mounts_poll,
 };
 
-extern const struct seq_operations mountstats_op;
-static int mountstats_open(struct inode *inode, struct file *file)
+static int mountinfo_open(struct inode *inode, struct file *file)
 {
-        int ret = seq_open(file, &mountstats_op);
-
-        if (!ret) {
-                struct seq_file *m = file->private_data;
-                struct nsproxy *nsp;
-                struct mnt_namespace *mnt_ns = NULL;
-                struct task_struct *task = get_proc_task(inode);
-
-                if (task) {
-                        rcu_read_lock();
-                        nsp = task_nsproxy(task);
-                        if (nsp) {
-                                mnt_ns = nsp->mnt_ns;
-                                if (mnt_ns)
-                                        get_mnt_ns(mnt_ns);
-                        }
-                        rcu_read_unlock();
+        return mounts_open_common(inode, file, &mountinfo_op);
+}
 
-                        put_task_struct(task);
-                }
+static const struct file_operations proc_mountinfo_operations = {
+        .open           = mountinfo_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = mounts_release,
+        .poll           = mounts_poll,
+};
 
-                if (mnt_ns)
-                        m->private = mnt_ns;
-                else {
-                        seq_release(inode, file);
-                        ret = -EINVAL;
-                }
-        }
-        return ret;
+static int mountstats_open(struct inode *inode, struct file *file)
+{
+        return mounts_open_common(inode, file, &mountstats_op);
 }
 
 static const struct file_operations proc_mountstats_operations = {
@@ -2309,6 +2316,7 @@ static const struct pid_entry tgid_base_stuff[] = {
         LNK("root",       root),
         LNK("exe",        exe),
         REG("mounts",     S_IRUGO, mounts),
+        REG("mountinfo",  S_IRUGO, mountinfo),
         REG("mountstats", S_IRUSR, mountstats),
 #ifdef CONFIG_PROC_PAGE_MONITOR
         REG("clear_refs", S_IWUSR, clear_refs),
@@ -2641,6 +2649,7 @@ static const struct pid_entry tid_base_stuff[] = {
         LNK("root",      root),
         LNK("exe",       exe),
         REG("mounts",    S_IRUGO, mounts),
+        REG("mountinfo",  S_IRUGO, mountinfo),
 #ifdef CONFIG_PROC_PAGE_MONITOR
         REG("clear_refs", S_IWUSR, clear_refs),
         REG("smaps",     S_IRUGO, smaps),
diff --git a/fs/seq_file.c b/fs/seq_file.c
index cdfd996ca6ef..3f54dbd6c49b 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -350,28 +350,40 @@ int seq_printf(struct seq_file *m, const char *f, ...)
 }
 EXPORT_SYMBOL(seq_printf);
 
+static char *mangle_path(char *s, char *p, char *esc)
+{
+        while (s <= p) {
+                char c = *p++;
+                if (!c) {
+                        return s;
+                } else if (!strchr(esc, c)) {
+                        *s++ = c;
+                } else if (s + 4 > p) {
+                        break;
+                } else {
+                        *s++ = '\\';
+                        *s++ = '0' + ((c & 0300) >> 6);
+                        *s++ = '0' + ((c & 070) >> 3);
+                        *s++ = '0' + (c & 07);
+                }
+        }
+        return NULL;
+}
+
+/*
+ * return the absolute path of 'dentry' residing in mount 'mnt'.
+ */
 int seq_path(struct seq_file *m, struct path *path, char *esc)
 {
         if (m->count < m->size) {
                 char *s = m->buf + m->count;
                 char *p = d_path(path, s, m->size - m->count);
                 if (!IS_ERR(p)) {
-                        while (s <= p) {
-                                char c = *p++;
-                                if (!c) {
-                                        p = m->buf + m->count;
-                                        m->count = s - m->buf;
-                                        return s - p;
-                                } else if (!strchr(esc, c)) {
-                                        *s++ = c;
-                                } else if (s + 4 > p) {
-                                        break;
-                                } else {
-                                        *s++ = '\\';
-                                        *s++ = '0' + ((c & 0300) >> 6);
-                                        *s++ = '0' + ((c & 070) >> 3);
-                                        *s++ = '0' + (c & 07);
-                                }
+                        s = mangle_path(s, p, esc);
+                        if (s) {
+                                p = m->buf + m->count;
+                                m->count = s - m->buf;
+                                return s - p;
                         }
                 }
         }
@@ -380,6 +392,57 @@ int seq_path(struct seq_file *m, struct path *path, char *esc)
 }
 EXPORT_SYMBOL(seq_path);
 
+/*
+ * Same as seq_path, but relative to supplied root.
+ *
+ * root may be changed, see __d_path().
+ */
+int seq_path_root(struct seq_file *m, struct path *path, struct path *root,
+                  char *esc)
+{
+        int err = -ENAMETOOLONG;
+        if (m->count < m->size) {
+                char *s = m->buf + m->count;
+                char *p;
+
+                spin_lock(&dcache_lock);
+                p = __d_path(path, root, s, m->size - m->count);
+                spin_unlock(&dcache_lock);
+                err = PTR_ERR(p);
+                if (!IS_ERR(p)) {
+                        s = mangle_path(s, p, esc);
+                        if (s) {
+                                p = m->buf + m->count;
+                                m->count = s - m->buf;
+                                return 0;
+                        }
+                }
+        }
+        m->count = m->size;
+        return err;
+}
+
+/*
+ * returns the path of the 'dentry' from the root of its filesystem.
+ */
+int seq_dentry(struct seq_file *m, struct dentry *dentry, char *esc)
+{
+        if (m->count < m->size) {
+                char *s = m->buf + m->count;
+                char *p = dentry_path(dentry, s, m->size - m->count);
+                if (!IS_ERR(p)) {
+                        s = mangle_path(s, p, esc);
+                        if (s) {
+                                p = m->buf + m->count;
+                                m->count = s - m->buf;
+                                return s - p;
+                        }
+                }
+        }
+        m->count = m->size;
+        return -1;
+}
+
 static void *single_start(struct seq_file *p, loff_t *pos)
 {
         return NULL + (*pos == 0);
diff --git a/fs/xattr.c b/fs/xattr.c
index f7062da505d4..89a942f07e1b 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -307,7 +307,6 @@ sys_fsetxattr(int fd, char __user *name, void __user *value,
                 error = setxattr(dentry, name, value, size, flags);
                 mnt_drop_write(f->f_path.mnt);
         }
-out_fput:
         fput(f);
         return error;
 }
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index fabd16d03a27..cfb1627ac51c 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -301,7 +301,9 @@ extern int d_validate(struct dentry *, struct dentry *);
  */
 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 
+extern char *__d_path(const struct path *path, struct path *root, char *, int);
 extern char *d_path(struct path *, char *, int);
+extern char *dentry_path(struct dentry *, char *, int);
 
 /* Allocation counts.. */
 
diff --git a/include/linux/mnt_namespace.h b/include/linux/mnt_namespace.h
index 8eed44f8ca73..830bbcd449d6 100644
--- a/include/linux/mnt_namespace.h
+++ b/include/linux/mnt_namespace.h
@@ -5,6 +5,7 @@
 #include <linux/mount.h>
 #include <linux/sched.h>
 #include <linux/nsproxy.h>
+#include <linux/seq_file.h>
 
 struct mnt_namespace {
         atomic_t                count;
@@ -14,6 +15,13 @@ struct mnt_namespace {
         int event;
 };
 
+struct proc_mounts {
+        struct seq_file m; /* must be the first element */
+        struct mnt_namespace *ns;
+        struct path root;
+        int event;
+};
+
 extern struct mnt_namespace *copy_mnt_ns(unsigned long, struct mnt_namespace *,
                 struct fs_struct *);
 extern void __put_mnt_ns(struct mnt_namespace *ns);
@@ -37,5 +45,9 @@ static inline void get_mnt_ns(struct mnt_namespace *ns)
         atomic_inc(&ns->count);
 }
 
+extern const struct seq_operations mounts_op;
+extern const struct seq_operations mountinfo_op;
+extern const struct seq_operations mountstats_op;
+
 #endif
 #endif
diff --git a/include/linux/mount.h b/include/linux/mount.h
index 87b24cea1863..b4836d58f428 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -56,6 +56,8 @@ struct vfsmount {
         struct list_head mnt_slave;     /* slave list entry */
         struct vfsmount *mnt_master;    /* slave is on master->mnt_slave_list */
         struct mnt_namespace *mnt_ns;   /* containing namespace */
+        int mnt_id;                     /* mount identifier */
+        int mnt_group_id;               /* peer group identifier */
         /*
          * We put mnt_count & mnt_expiry_mark at the end of struct vfsmount
          * to let these frequently modified fields in a separate cache line
diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
index d65796dc26d9..5b5369c3c209 100644
--- a/include/linux/seq_file.h
+++ b/include/linux/seq_file.h
@@ -10,6 +10,7 @@ struct seq_operations;
 struct file;
 struct path;
 struct inode;
+struct dentry;
 
 struct seq_file {
         char *buf;
@@ -44,6 +45,9 @@ int seq_printf(struct seq_file *, const char *, ...)
         __attribute__ ((format (printf,2,3)));
 
 int seq_path(struct seq_file *, struct path *, char *);
+int seq_dentry(struct seq_file *, struct dentry *, char *);
+int seq_path_root(struct seq_file *m, struct path *path, struct path *root,
+                  char *esc);
 
 int single_open(struct file *, int (*)(struct seq_file *, void *), void *);
 int single_release(struct inode *, struct file *);