1 files changed, 579 insertions, 68 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 94f026ec990a..0505fb61aa74 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -17,6 +17,7 @@
 #include <linux/quotaops.h>
 #include <linux/acct.h>
 #include <linux/capability.h>
+#include <linux/cpumask.h>
 #include <linux/module.h>
 #include <linux/sysfs.h>
 #include <linux/seq_file.h>
@@ -26,6 +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"
@@ -38,6 +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;
@@ -55,10 +59,65 @@ static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
         return tmp & (HASH_SIZE - 1);
 }
 
+#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);
@@ -68,6 +127,7 @@ struct vfsmount *alloc_vfsmnt(const char *name)
                 INIT_LIST_HEAD(&mnt->mnt_share);
                 INIT_LIST_HEAD(&mnt->mnt_slave_list);
                 INIT_LIST_HEAD(&mnt->mnt_slave);
+                atomic_set(&mnt->__mnt_writers, 0);
                 if (name) {
                         int size = strlen(name) + 1;
                         char *newname = kmalloc(size, GFP_KERNEL);
@@ -80,6 +140,263 @@ struct vfsmount *alloc_vfsmnt(const char *name)
         return mnt;
 }
 
+/*
+ * Most r/o checks on a fs are for operations that take
+ * discrete amounts of time, like a write() or unlink().
+ * We must keep track of when those operations start
+ * (for permission checks) and when they end, so that
+ * we can determine when writes are able to occur to
+ * a filesystem.
+ */
+/*
+ * __mnt_is_readonly: check whether a mount is read-only
+ * @mnt: the mount to check for its write status
+ *
+ * This shouldn't be used directly ouside of the VFS.
+ * It does not guarantee that the filesystem will stay
+ * r/w, just that it is right *now*.  This can not and
+ * should not be used in place of IS_RDONLY(inode).
+ * mnt_want/drop_write() will _keep_ the filesystem
+ * r/w.
+ */
+int __mnt_is_readonly(struct vfsmount *mnt)
+{
+        if (mnt->mnt_flags & MNT_READONLY)
+                return 1;
+        if (mnt->mnt_sb->s_flags & MS_RDONLY)
+                return 1;
+        return 0;
+}
+EXPORT_SYMBOL_GPL(__mnt_is_readonly);
+
+struct mnt_writer {
+        /*
+         * If holding multiple instances of this lock, they
+         * must be ordered by cpu number.
+         */
+        spinlock_t lock;
+        struct lock_class_key lock_class; /* compiles out with !lockdep */
+        unsigned long count;
+        struct vfsmount *mnt;
+} ____cacheline_aligned_in_smp;
+static DEFINE_PER_CPU(struct mnt_writer, mnt_writers);
+
+static int __init init_mnt_writers(void)
+{
+        int cpu;
+        for_each_possible_cpu(cpu) {
+                struct mnt_writer *writer = &per_cpu(mnt_writers, cpu);
+                spin_lock_init(&writer->lock);
+                lockdep_set_class(&writer->lock, &writer->lock_class);
+                writer->count = 0;
+        }
+        return 0;
+}
+fs_initcall(init_mnt_writers);
+
+static void unlock_mnt_writers(void)
+{
+        int cpu;
+        struct mnt_writer *cpu_writer;
+
+        for_each_possible_cpu(cpu) {
+                cpu_writer = &per_cpu(mnt_writers, cpu);
+                spin_unlock(&cpu_writer->lock);
+        }
+}
+
+static inline void __clear_mnt_count(struct mnt_writer *cpu_writer)
+{
+        if (!cpu_writer->mnt)
+                return;
+        /*
+         * This is in case anyone ever leaves an invalid,
+         * old ->mnt and a count of 0.
+         */
+        if (!cpu_writer->count)
+                return;
+        atomic_add(cpu_writer->count, &cpu_writer->mnt->__mnt_writers);
+        cpu_writer->count = 0;
+}
+ /*
+ * must hold cpu_writer->lock
+ */
+static inline void use_cpu_writer_for_mount(struct mnt_writer *cpu_writer,
+                                          struct vfsmount *mnt)
+{
+        if (cpu_writer->mnt == mnt)
+                return;
+        __clear_mnt_count(cpu_writer);
+        cpu_writer->mnt = mnt;
+}
+
+/*
+ * Most r/o checks on a fs are for operations that take
+ * discrete amounts of time, like a write() or unlink().
+ * We must keep track of when those operations start
+ * (for permission checks) and when they end, so that
+ * we can determine when writes are able to occur to
+ * a filesystem.
+ */
+/**
+ * mnt_want_write - get write access to a mount
+ * @mnt: the mount on which to take a write
+ *
+ * This tells the low-level filesystem that a write is
+ * about to be performed to it, and makes sure that
+ * writes are allowed before returning success.  When
+ * the write operation is finished, mnt_drop_write()
+ * must be called.  This is effectively a refcount.
+ */
+int mnt_want_write(struct vfsmount *mnt)
+{
+        int ret = 0;
+        struct mnt_writer *cpu_writer;
+
+        cpu_writer = &get_cpu_var(mnt_writers);
+        spin_lock(&cpu_writer->lock);
+        if (__mnt_is_readonly(mnt)) {
+                ret = -EROFS;
+                goto out;
+        }
+        use_cpu_writer_for_mount(cpu_writer, mnt);
+        cpu_writer->count++;
+out:
+        spin_unlock(&cpu_writer->lock);
+        put_cpu_var(mnt_writers);
+        return ret;
+}
+EXPORT_SYMBOL_GPL(mnt_want_write);
+
+static void lock_mnt_writers(void)
+{
+        int cpu;
+        struct mnt_writer *cpu_writer;
+
+        for_each_possible_cpu(cpu) {
+                cpu_writer = &per_cpu(mnt_writers, cpu);
+                spin_lock(&cpu_writer->lock);
+                __clear_mnt_count(cpu_writer);
+                cpu_writer->mnt = NULL;
+        }
+}
+
+/*
+ * These per-cpu write counts are not guaranteed to have
+ * matched increments and decrements on any given cpu.
+ * A file open()ed for write on one cpu and close()d on
+ * another cpu will imbalance this count.  Make sure it
+ * does not get too far out of whack.
+ */
+static void handle_write_count_underflow(struct vfsmount *mnt)
+{
+        if (atomic_read(&mnt->__mnt_writers) >=
+            MNT_WRITER_UNDERFLOW_LIMIT)
+                return;
+        /*
+         * It isn't necessary to hold all of the locks
+         * at the same time, but doing it this way makes
+         * us share a lot more code.
+         */
+        lock_mnt_writers();
+        /*
+         * vfsmount_lock is for mnt_flags.
+         */
+        spin_lock(&vfsmount_lock);
+        /*
+         * If coalescing the per-cpu writer counts did not
+         * get us back to a positive writer count, we have
+         * a bug.
+         */
+        if ((atomic_read(&mnt->__mnt_writers) < 0) &&
+            !(mnt->mnt_flags & MNT_IMBALANCED_WRITE_COUNT)) {
+                printk(KERN_DEBUG "leak detected on mount(%p) writers "
+                                "count: %d\n",
+                        mnt, atomic_read(&mnt->__mnt_writers));
+                WARN_ON(1);
+                /* use the flag to keep the dmesg spam down */
+                mnt->mnt_flags |= MNT_IMBALANCED_WRITE_COUNT;
+        }
+        spin_unlock(&vfsmount_lock);
+        unlock_mnt_writers();
+}
+
+/**
+ * mnt_drop_write - give up write access to a mount
+ * @mnt: the mount on which to give up write access
+ *
+ * Tells the low-level filesystem that we are done
+ * performing writes to it.  Must be matched with
+ * mnt_want_write() call above.
+ */
+void mnt_drop_write(struct vfsmount *mnt)
+{
+        int must_check_underflow = 0;
+        struct mnt_writer *cpu_writer;
+
+        cpu_writer = &get_cpu_var(mnt_writers);
+        spin_lock(&cpu_writer->lock);
+
+        use_cpu_writer_for_mount(cpu_writer, mnt);
+        if (cpu_writer->count > 0) {
+                cpu_writer->count--;
+        } else {
+                must_check_underflow = 1;
+                atomic_dec(&mnt->__mnt_writers);
+        }
+
+        spin_unlock(&cpu_writer->lock);
+        /*
+         * Logically, we could call this each time,
+         * but the __mnt_writers cacheline tends to
+         * be cold, and makes this expensive.
+         */
+        if (must_check_underflow)
+                handle_write_count_underflow(mnt);
+        /*
+         * This could be done right after the spinlock
+         * is taken because the spinlock keeps us on
+         * the cpu, and disables preemption.  However,
+         * putting it here bounds the amount that
+         * __mnt_writers can underflow.  Without it,
+         * we could theoretically wrap __mnt_writers.
+         */
+        put_cpu_var(mnt_writers);
+}
+EXPORT_SYMBOL_GPL(mnt_drop_write);
+
+static int mnt_make_readonly(struct vfsmount *mnt)
+{
+        int ret = 0;
+
+        lock_mnt_writers();
+        /*
+         * With all the locks held, this value is stable
+         */
+        if (atomic_read(&mnt->__mnt_writers) > 0) {
+                ret = -EBUSY;
+                goto out;
+        }
+        /*
+         * nobody can do a successful mnt_want_write() with all
+         * of the counts in MNT_DENIED_WRITE and the locks held.
+         */
+        spin_lock(&vfsmount_lock);
+        if (!ret)
+                mnt->mnt_flags |= MNT_READONLY;
+        spin_unlock(&vfsmount_lock);
+out:
+        unlock_mnt_writers();
+        return ret;
+}
+
+static void __mnt_unmake_readonly(struct vfsmount *mnt)
+{
+        spin_lock(&vfsmount_lock);
+        mnt->mnt_flags &= ~MNT_READONLY;
+        spin_unlock(&vfsmount_lock);
+}
+
 int simple_set_mnt(struct vfsmount *mnt, struct super_block *sb)
 {
         mnt->mnt_sb = sb;
@@ -92,6 +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);
 }
 
@@ -238,6 +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;
@@ -267,11 +596,44 @@ 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)
 {
+        int cpu;
         struct super_block *sb = mnt->mnt_sb;
+        /*
+         * We don't have to hold all of the locks at the
+         * same time here because we know that we're the
+         * last reference to mnt and that no new writers
+         * can come in.
+         */
+        for_each_possible_cpu(cpu) {
+                struct mnt_writer *cpu_writer = &per_cpu(mnt_writers, cpu);
+                if (cpu_writer->mnt != mnt)
+                        continue;
+                spin_lock(&cpu_writer->lock);
+                atomic_add(cpu_writer->count, &mnt->__mnt_writers);
+                cpu_writer->count = 0;
+                /*
+                 * Might as well do this so that no one
+                 * ever sees the pointer and expects
+                 * it to be valid.
+                 */
+                cpu_writer->mnt = NULL;
+                spin_unlock(&cpu_writer->lock);
+        }
+        /*
+         * 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.
+         */
+        WARN_ON(atomic_read(&mnt->__mnt_writers));
         dput(mnt->mnt_root);
         free_vfsmnt(mnt);
         deactivate_super(sb);
@@ -362,20 +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)
@@ -383,20 +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" },
@@ -405,40 +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);
-        }
-        seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? " 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_type(m, mnt->mnt_sb);
+        seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");
+        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);
@@ -459,7 +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) {
@@ -471,12 +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
@@ -801,23 +1243,50 @@ Enomem:
 struct vfsmount *collect_mounts(struct vfsmount *mnt, struct dentry *dentry)
 {
         struct vfsmount *tree;
-        down_read(&namespace_sem);
+        down_write(&namespace_sem);
         tree = copy_tree(mnt, dentry, CL_COPY_ALL | CL_PRIVATE);
-        up_read(&namespace_sem);
+        up_write(&namespace_sem);
         return tree;
 }
 
 void drop_collected_mounts(struct vfsmount *mnt)
 {
         LIST_HEAD(umount_list);
-        down_read(&namespace_sem);
+        down_write(&namespace_sem);
         spin_lock(&vfsmount_lock);
         umount_tree(mnt, 0, &umount_list);
         spin_unlock(&vfsmount_lock);
-        up_read(&namespace_sem);
+        up_write(&namespace_sem);
         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
@@ -888,9 +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))
@@ -913,34 +1389,40 @@ 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 nameidata *nd)
+static int graft_tree(struct vfsmount *mnt, struct path *path)
 {
         int err;
         if (mnt->mnt_sb->s_flags & MS_NOUSER)
                 return -EINVAL;
 
-        if (S_ISDIR(nd->path.dentry->d_inode->i_mode) !=
+        if (S_ISDIR(path->dentry->d_inode->i_mode) !=
               S_ISDIR(mnt->mnt_root->d_inode->i_mode))
                 return -ENOTDIR;
 
         err = -ENOENT;
-        mutex_lock(&nd->path.dentry->d_inode->i_mutex);
-        if (IS_DEADDIR(nd->path.dentry->d_inode))
+        mutex_lock(&path->dentry->d_inode->i_mutex);
+        if (IS_DEADDIR(path->dentry->d_inode))
                 goto out_unlock;
 
-        err = security_sb_check_sb(mnt, nd);
+        err = security_sb_check_sb(mnt, path);
         if (err)
                 goto out_unlock;
 
         err = -ENOENT;
-        if (IS_ROOT(nd->path.dentry) || !d_unhashed(nd->path.dentry))
-                err = attach_recursive_mnt(mnt, &nd->path, NULL);
+        if (IS_ROOT(path->dentry) || !d_unhashed(path->dentry))
+                err = attach_recursive_mnt(mnt, path, NULL);
 out_unlock:
-        mutex_unlock(&nd->path.dentry->d_inode->i_mutex);
+        mutex_unlock(&path->dentry->d_inode->i_mutex);
         if (!err)
-                security_sb_post_addmount(mnt, nd);
+                security_sb_post_addmount(mnt, path);
         return err;
 }
 
@@ -953,6 +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;
@@ -961,12 +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;
 }
 
 /*
@@ -1004,7 +1495,7 @@ static noinline int do_loopback(struct nameidata *nd, char *old_name,
         if (!mnt)
                 goto out;
 
-        err = graft_tree(mnt, nd);
+        err = graft_tree(mnt, &nd->path);
         if (err) {
                 LIST_HEAD(umount_list);
                 spin_lock(&vfsmount_lock);
@@ -1019,6 +1510,23 @@ out:
         return err;
 }
 
+static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
+{
+        int error = 0;
+        int readonly_request = 0;
+
+        if (ms_flags & MS_RDONLY)
+                readonly_request = 1;
+        if (readonly_request == __mnt_is_readonly(mnt))
+                return 0;
+
+        if (readonly_request)
+                error = mnt_make_readonly(mnt);
+        else
+                __mnt_unmake_readonly(mnt);
+        return error;
+}
+
 /*
  * change filesystem flags. dir should be a physical root of filesystem.
  * If you've mounted a non-root directory somewhere and want to do remount
@@ -1041,7 +1549,10 @@ static noinline int do_remount(struct nameidata *nd, int flags, int mnt_flags,
                 return -EINVAL;
 
         down_write(&sb->s_umount);
-        err = do_remount_sb(sb, flags, data, 0);
+        if (flags & MS_BIND)
+                err = change_mount_flags(nd->path.mnt, flags);
+        else
+                err = do_remount_sb(sb, flags, data, 0);
         if (!err)
                 nd->path.mnt->mnt_flags = mnt_flags;
         up_write(&sb->s_umount);
@@ -1191,7 +1702,7 @@ int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd,
                 goto unlock;
 
         newmnt->mnt_flags = mnt_flags;
-        if ((err = graft_tree(newmnt, nd)))
+        if ((err = graft_tree(newmnt, &nd->path)))
                 goto unlock;
 
         if (fslist) /* add to the specified expiration list */
@@ -1425,6 +1936,8 @@ long do_mount(char *dev_name, char *dir_name, char *type_page,
                 mnt_flags |= MNT_NODIRATIME;
         if (flags & MS_RELATIME)
                 mnt_flags |= MNT_RELATIME;
+        if (flags & MS_RDONLY)
+                mnt_flags |= MNT_READONLY;
 
         flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE |
                    MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT);
@@ -1434,7 +1947,8 @@ long do_mount(char *dev_name, char *dir_name, char *type_page,
         if (retval)
                 return retval;
 
-        retval = security_sb_mount(dev_name, &nd, type_page, flags, data_page);
+        retval = security_sb_mount(dev_name, &nd.path,
+                                   type_page, flags, data_page);
         if (retval)
                 goto dput_out;
 
@@ -1674,15 +2188,13 @@ asmlinkage long sys_pivot_root(const char __user * new_root,
                                const char __user * put_old)
 {
         struct vfsmount *tmp;
-        struct nameidata new_nd, old_nd, user_nd;
-        struct path parent_path, root_parent;
+        struct nameidata new_nd, old_nd;
+        struct path parent_path, root_parent, root;
         int error;
 
         if (!capable(CAP_SYS_ADMIN))
                 return -EPERM;
 
-        lock_kernel();
-
         error = __user_walk(new_root, LOOKUP_FOLLOW | LOOKUP_DIRECTORY,
                             &new_nd);
         if (error)
@@ -1695,14 +2207,14 @@ asmlinkage long sys_pivot_root(const char __user * new_root,
         if (error)
                 goto out1;
 
-        error = security_sb_pivotroot(&old_nd, &new_nd);
+        error = security_sb_pivotroot(&old_nd.path, &new_nd.path);
         if (error) {
                 path_put(&old_nd.path);
                 goto out1;
         }
 
         read_lock(&current->fs->lock);
-        user_nd.path = current->fs->root;
+        root = current->fs->root;
         path_get(&current->fs->root);
         read_unlock(&current->fs->lock);
         down_write(&namespace_sem);
@@ -1710,9 +2222,9 @@ asmlinkage long sys_pivot_root(const char __user * new_root,
         error = -EINVAL;
         if (IS_MNT_SHARED(old_nd.path.mnt) ||
                 IS_MNT_SHARED(new_nd.path.mnt->mnt_parent) ||
-                IS_MNT_SHARED(user_nd.path.mnt->mnt_parent))
+                IS_MNT_SHARED(root.mnt->mnt_parent))
                 goto out2;
-        if (!check_mnt(user_nd.path.mnt))
+        if (!check_mnt(root.mnt))
                 goto out2;
         error = -ENOENT;
         if (IS_DEADDIR(new_nd.path.dentry->d_inode))
@@ -1722,13 +2234,13 @@ asmlinkage long sys_pivot_root(const char __user * new_root,
         if (d_unhashed(old_nd.path.dentry) && !IS_ROOT(old_nd.path.dentry))
                 goto out2;
         error = -EBUSY;
-        if (new_nd.path.mnt == user_nd.path.mnt ||
-            old_nd.path.mnt == user_nd.path.mnt)
+        if (new_nd.path.mnt == root.mnt ||
+            old_nd.path.mnt == root.mnt)
                 goto out2; /* loop, on the same file system  */
         error = -EINVAL;
-        if (user_nd.path.mnt->mnt_root != user_nd.path.dentry)
+        if (root.mnt->mnt_root != root.dentry)
                 goto out2; /* not a mountpoint */
-        if (user_nd.path.mnt->mnt_parent == user_nd.path.mnt)
+        if (root.mnt->mnt_parent == root.mnt)
                 goto out2; /* not attached */
         if (new_nd.path.mnt->mnt_root != new_nd.path.dentry)
                 goto out2; /* not a mountpoint */
@@ -1750,27 +2262,26 @@ asmlinkage long sys_pivot_root(const char __user * new_root,
         } else if (!is_subdir(old_nd.path.dentry, new_nd.path.dentry))
                 goto out3;
         detach_mnt(new_nd.path.mnt, &parent_path);
-        detach_mnt(user_nd.path.mnt, &root_parent);
+        detach_mnt(root.mnt, &root_parent);
         /* mount old root on put_old */
-        attach_mnt(user_nd.path.mnt, &old_nd.path);
+        attach_mnt(root.mnt, &old_nd.path);
         /* mount new_root on / */
         attach_mnt(new_nd.path.mnt, &root_parent);
         touch_mnt_namespace(current->nsproxy->mnt_ns);
         spin_unlock(&vfsmount_lock);
-        chroot_fs_refs(&user_nd.path, &new_nd.path);
-        security_sb_post_pivotroot(&user_nd, &new_nd);
+        chroot_fs_refs(&root, &new_nd.path);
+        security_sb_post_pivotroot(&root, &new_nd.path);
         error = 0;
         path_put(&root_parent);
         path_put(&parent_path);
 out2:
         mutex_unlock(&old_nd.path.dentry->d_inode->i_mutex);
         up_write(&namespace_sem);
-        path_put(&user_nd.path);
+        path_put(&root);
         path_put(&old_nd.path);
 out1:
         path_put(&new_nd.path);
 out0:
-        unlock_kernel();
         return error;
 out3:
         spin_unlock(&vfsmount_lock);