1 files changed, 64 insertions, 3 deletions

diff --git a/fs/super.c b/fs/super.c
index 0e7207b9815c..19eb70b374bc 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -465,6 +465,48 @@ rescan:
 }
 
 EXPORT_SYMBOL(get_super);
+
+/**
+ * get_active_super - get an active reference to 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.  Returns the superblock with an active
+ * reference and s_umount held exclusively or %NULL if none was found.
+ */
+struct super_block *get_active_super(struct block_device *bdev)
+{
+        struct super_block *sb;
+
+        if (!bdev)
+                return NULL;
+
+        spin_lock(&sb_lock);
+        list_for_each_entry(sb, &super_blocks, s_list) {
+                if (sb->s_bdev != bdev)
+                        continue;
+
+                sb->s_count++;
+                spin_unlock(&sb_lock);
+                down_write(&sb->s_umount);
+                if (sb->s_root) {
+                        spin_lock(&sb_lock);
+                        if (sb->s_count > S_BIAS) {
+                                atomic_inc(&sb->s_active);
+                                sb->s_count--;
+                                spin_unlock(&sb_lock);
+                                return sb;
+                        }
+                        spin_unlock(&sb_lock);
+                }
+                up_write(&sb->s_umount);
+                put_super(sb);
+                yield();
+                spin_lock(&sb_lock);
+        }
+        spin_unlock(&sb_lock);
+        return NULL;
+}
  
 struct super_block * user_get_super(dev_t dev)
 {
@@ -527,11 +569,15 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
 {
         int retval;
         int remount_rw;
-        
+
+        if (sb->s_frozen != SB_UNFROZEN)
+                return -EBUSY;
+
 #ifdef CONFIG_BLOCK
         if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
                 return -EACCES;
 #endif
+
         if (flags & MS_RDONLY)
                 acct_auto_close(sb);
         shrink_dcache_sb(sb);
@@ -743,9 +789,14 @@ int get_sb_bdev(struct file_system_type *fs_type,
          * will protect the lockfs code from trying to start a snapshot
          * while we are mounting
          */
-        down(&bdev->bd_mount_sem);
+        mutex_lock(&bdev->bd_fsfreeze_mutex);
+        if (bdev->bd_fsfreeze_count > 0) {
+                mutex_unlock(&bdev->bd_fsfreeze_mutex);
+                error = -EBUSY;
+                goto error_bdev;
+        }
         s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
-        up(&bdev->bd_mount_sem);
+        mutex_unlock(&bdev->bd_fsfreeze_mutex);
         if (IS_ERR(s))
                 goto error_s;
 
@@ -892,6 +943,16 @@ vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void
         if (error)
                 goto out_sb;
 
+        /*
+         * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
+         * but s_maxbytes was an unsigned long long for many releases. Throw
+         * this warning for a little while to try and catch filesystems that
+         * violate this rule. This warning should be either removed or
+         * converted to a BUG() in 2.6.34.
+         */
+        WARN((mnt->mnt_sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
+                "negative value (%lld)\n", type->name, mnt->mnt_sb->s_maxbytes);
+
         mnt->mnt_mountpoint = mnt->mnt_root;
         mnt->mnt_parent = mnt;
         up_write(&mnt->mnt_sb->s_umount);