1 files changed, 60 insertions, 21 deletions

diff --git a/fs/super.c b/fs/super.c
index c183835566c1..1709ed029a2c 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -244,7 +244,6 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
         mutex_init(&s->s_vfs_rename_mutex);
         lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key);
         mutex_init(&s->s_dquot.dqio_mutex);
-        mutex_init(&s->s_dquot.dqonoff_mutex);
         s->s_maxbytes = MAX_NON_LFS;
         s->s_op = &default_op;
         s->s_time_gran = 1000000000;
@@ -558,6 +557,13 @@ void drop_super(struct super_block *sb)
 
 EXPORT_SYMBOL(drop_super);
 
+void drop_super_exclusive(struct super_block *sb)
+{
+        up_write(&sb->s_umount);
+        put_super(sb);
+}
+EXPORT_SYMBOL(drop_super_exclusive);
+
 /**
  *      iterate_supers - call function for all active superblocks
  *      @f: function to call
@@ -628,15 +634,7 @@ void iterate_supers_type(struct file_system_type *type,
 
 EXPORT_SYMBOL(iterate_supers_type);
 
-/**
- *      get_super - get the superblock of a device
- *      @bdev: device to get the superblock for
- *      
- *      Scans the superblock list and finds the superblock of the file system
- *      mounted on the device given. %NULL is returned if no match is found.
- */
-
-struct super_block *get_super(struct block_device *bdev)
+static struct super_block *__get_super(struct block_device *bdev, bool excl)
 {
         struct super_block *sb;
 
@@ -651,11 +649,17 @@ rescan:
                 if (sb->s_bdev == bdev) {
                         sb->s_count++;
                         spin_unlock(&sb_lock);
-                        down_read(&sb->s_umount);
+                        if (!excl)
+                                down_read(&sb->s_umount);
+                        else
+                                down_write(&sb->s_umount);
                         /* still alive? */
                         if (sb->s_root && (sb->s_flags & MS_BORN))
                                 return sb;
-                        up_read(&sb->s_umount);
+                        if (!excl)
+                                up_read(&sb->s_umount);
+                        else
+                                up_write(&sb->s_umount);
                         /* nope, got unmounted */
                         spin_lock(&sb_lock);
                         __put_super(sb);
@@ -666,32 +670,67 @@ rescan:
         return NULL;
 }
 
-EXPORT_SYMBOL(get_super);
-
 /**
- *      get_super_thawed - get thawed superblock of a device
+ *      get_super - get the superblock of a device
  *      @bdev: device to get the superblock for
  *
  *      Scans the superblock list and finds the superblock of the file system
- *      mounted on the device. The superblock is returned once it is thawed
- *      (or immediately if it was not frozen). %NULL is returned if no match
- *      is found.
+ *      mounted on the device given. %NULL is returned if no match is found.
  */
-struct super_block *get_super_thawed(struct block_device *bdev)
+struct super_block *get_super(struct block_device *bdev)
+{
+        return __get_super(bdev, false);
+}
+EXPORT_SYMBOL(get_super);
+
+static struct super_block *__get_super_thawed(struct block_device *bdev,
+                                              bool excl)
 {
         while (1) {
-                struct super_block *s = get_super(bdev);
+                struct super_block *s = __get_super(bdev, excl);
                 if (!s || s->s_writers.frozen == SB_UNFROZEN)
                         return s;
-                up_read(&s->s_umount);
+                if (!excl)
+                        up_read(&s->s_umount);
+                else
+                        up_write(&s->s_umount);
                 wait_event(s->s_writers.wait_unfrozen,
                            s->s_writers.frozen == SB_UNFROZEN);
                 put_super(s);
         }
 }
+
+/**
+ *      get_super_thawed - get thawed superblock of a device
+ *      @bdev: device to get the superblock for
+ *
+ *      Scans the superblock list and finds the superblock of the file system
+ *      mounted on the device. The superblock is returned once it is thawed
+ *      (or immediately if it was not frozen). %NULL is returned if no match
+ *      is found.
+ */
+struct super_block *get_super_thawed(struct block_device *bdev)
+{
+        return __get_super_thawed(bdev, false);
+}
 EXPORT_SYMBOL(get_super_thawed);
 
 /**
+ *      get_super_exclusive_thawed - get thawed superblock of a device
+ *      @bdev: device to get the superblock for
+ *
+ *      Scans the superblock list and finds the superblock of the file system
+ *      mounted on the device. The superblock is returned once it is thawed
+ *      (or immediately if it was not frozen) and s_umount semaphore is held
+ *      in exclusive mode. %NULL is returned if no match is found.
+ */
+struct super_block *get_super_exclusive_thawed(struct block_device *bdev)
+{
+        return __get_super_thawed(bdev, true);
+}
+EXPORT_SYMBOL(get_super_exclusive_thawed);
+
+/**
  * get_active_super - get an active reference to the superblock of a device
  * @bdev: device to get the superblock for
  *