md/bitmap: tidy up i_writecount handling in md/bitmap

md/bitmap modifies i_writecount of a bitmap file to make sure that no-one else
writes to it.  The reverting of the change is sometimes done twice, and there
is one error path where it is omitted.

This patch tidies that up.
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Adrian Bunk <bunk@kernel.org>

drivers/md/bitmap.c

@@ -641,7 +641,6 @@ static void drain_write_queues(struct bitmap *bitmap)
 static void bitmap_file_put(struct bitmap *bitmap)
 {
 	struct file *file;
-	struct inode *inode;
 	unsigned long flags;
 
 	spin_lock_irqsave(&bitmap->lock, flags);
@@ -655,13 +654,8 @@ static void bitmap_file_put(struct bitmap *bitmap)
 
 	bitmap_file_unmap(bitmap);
 
-	if (file) {
-		inode = file->f_mapping->host;
-		spin_lock(&inode->i_lock);
-		atomic_set(&inode->i_writecount, 1); /* allow writes again */
-		spin_unlock(&inode->i_lock);
+	if (file)
 		fput(file);
-	}
 }
 
 

drivers/md/md.c

@@ -2644,6 +2644,32 @@ static int restart_array(mddev_t *mddev)
 	return err;
 }
 
+/* similar to deny_write_access, but accounts for our holding a reference
+ * to the file ourselves */
+static int deny_bitmap_write_access(struct file * file)
+{
+	struct inode *inode = file->f_mapping->host;
+
+	spin_lock(&inode->i_lock);
+	if (atomic_read(&inode->i_writecount) > 1) {
+		spin_unlock(&inode->i_lock);
+		return -ETXTBSY;
+	}
+	atomic_set(&inode->i_writecount, -1);
+	spin_unlock(&inode->i_lock);
+
+	return 0;
+}
+
+static void restore_bitmap_write_access(struct file *file)
+{
+	struct inode *inode = file->f_mapping->host;
+
+	spin_lock(&inode->i_lock);
+	atomic_set(&inode->i_writecount, 1);
+	spin_unlock(&inode->i_lock);
+}
+
 static int do_md_stop(mddev_t * mddev, int ro)
 {
 	int err = 0;
@@ -2705,7 +2731,7 @@ static int do_md_stop(mddev_t * mddev, int ro)
 
 		bitmap_destroy(mddev);
 		if (mddev->bitmap_file) {
-			atomic_set(&mddev->bitmap_file->f_dentry->d_inode->i_writecount, 1);
+			restore_bitmap_write_access(mddev->bitmap_file);
 			fput(mddev->bitmap_file);
 			mddev->bitmap_file = NULL;
 		}
@@ -3299,23 +3325,6 @@ static int hot_add_disk(mddev_t * mddev, dev_t dev)
 	return err;
 }
 
-/* similar to deny_write_access, but accounts for our holding a reference
- * to the file ourselves */
-static int deny_bitmap_write_access(struct file * file)
-{
-	struct inode *inode = file->f_mapping->host;
-
-	spin_lock(&inode->i_lock);
-	if (atomic_read(&inode->i_writecount) > 1) {
-		spin_unlock(&inode->i_lock);
-		return -ETXTBSY;
-	}
-	atomic_set(&inode->i_writecount, -1);
-	spin_unlock(&inode->i_lock);
-
-	return 0;
-}
-
 static int set_bitmap_file(mddev_t *mddev, int fd)
 {
 	int err;
@@ -3363,8 +3372,10 @@ static int set_bitmap_file(mddev_t *mddev, int fd)
 		mddev->pers->quiesce(mddev, 0);
 	}
 	if (fd < 0) {
-		if (mddev->bitmap_file)
+		if (mddev->bitmap_file) {
+			restore_bitmap_write_access(mddev->bitmap_file);
 			fput(mddev->bitmap_file);
+		}
 		mddev->bitmap_file = NULL;
 	}