[PATCH] clean up argument passing in writeback paths

The writeback code paths which walk the superblocks and inodes are
getting an increasing arguments passed to them.

The patch wraps those args into the new `struct writeback_control',
and uses that instead.  There is no functional change.

The new writeback_control structure is passed down through the
writeback paths in the place where the old `nr_to_write' pointer used
to be.

writeback_control will be used to pass new information up and down the
writeback paths.  Such as whether the writeback should be non-blocking,
and whether queue congestion was encountered.

3 files changed, 25 insertions, 13 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 622481a00115..e421e95b9320 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -279,6 +279,7 @@ struct iattr {
  */
 struct page;
 struct address_space;
+struct writeback_control;
 
 struct address_space_operations {
 	int (*writepage)(struct page *);
@@ -286,10 +287,10 @@ struct address_space_operations {
 	int (*sync_page)(struct page *);
 
 	/* Write back some dirty pages from this mapping. */
-	int (*writepages)(struct address_space *, int *nr_to_write);
+	int (*writepages)(struct address_space *, struct writeback_control *);
 
 	/* Perform a writeback as a memory-freeing operation. */
-	int (*vm_writeback)(struct page *, int *nr_to_write);
+	int (*vm_writeback)(struct page *, struct writeback_control *);
 
 	/* Set a page dirty */
 	int (*set_page_dirty)(struct page *page);
@@ -1261,7 +1262,8 @@ extern loff_t generic_file_llseek(struct file *file, loff_t offset, int origin);
 extern loff_t remote_llseek(struct file *file, loff_t offset, int origin);
 extern int generic_file_open(struct inode * inode, struct file * filp);
 
-extern int generic_vm_writeback(struct page *page, int *nr_to_write);
+extern int generic_vm_writeback(struct page *page,
+				struct writeback_control *wbc);
 
 extern struct file_operations generic_ro_fops;
 
diff --git a/include/linux/mpage.h b/include/linux/mpage.h
index 52253d90f55d..86aa7b676274 100644
--- a/include/linux/mpage.h
+++ b/include/linux/mpage.h
@@ -10,14 +10,16 @@
  * nested includes.  Get it right in the .c file).
  */
 
+struct writeback_control;
+
 int mpage_readpages(struct address_space *mapping, struct list_head *pages,
 				unsigned nr_pages, get_block_t get_block);
 int mpage_readpage(struct page *page, get_block_t get_block);
 int mpage_writepages(struct address_space *mapping,
-		int *nr_to_write, get_block_t get_block);
+		struct writeback_control *wbc, get_block_t get_block);
 
 static inline int
-generic_writepages(struct address_space *mapping, int *nr_to_write)
+generic_writepages(struct address_space *mapping, struct writeback_control *wbc)
 {
-	return mpage_writepages(mapping, nr_to_write, NULL);
+	return mpage_writepages(mapping, wbc, NULL);
 }
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 5de884cd6a7c..b12971f8eeb0 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -33,16 +33,24 @@ enum writeback_sync_modes {
 	WB_SYNC_HOLD =  3,	/* Hold the inode on sb_dirty for sys_sync() */
 };
 
-void writeback_unlocked_inodes(int *nr_to_write,
-			       enum writeback_sync_modes sync_mode,
-			       unsigned long *older_than_this);
+/*
+ * A control structure which tells the writeback code what to do
+ */
+struct writeback_control {
+	struct backing_dev_info *bdi;	/* If !NULL, only write back this
+					   queue */
+	enum writeback_sync_modes sync_mode;
+	unsigned long *older_than_this;	/* If !NULL, only write back inodes
+					   older than this */
+	long nr_to_write;		/* Write this many pages, and decrement
+					   this for each page written */
+};
+	
+void writeback_inodes(struct writeback_control *wbc);
 void wake_up_inode(struct inode *inode);
 void __wait_on_inode(struct inode * inode);
 void sync_inodes_sb(struct super_block *, int wait);
 void sync_inodes(int wait);
-void writeback_backing_dev(struct backing_dev_info *bdi, int *nr_to_write,
-			enum writeback_sync_modes sync_mode,
-			unsigned long *older_than_this);
 
 /* writeback.h requires fs.h; it, too, is not included from here. */
 static inline void wait_on_inode(struct inode *inode)
@@ -65,7 +73,7 @@ extern int dirty_expire_centisecs;
 void balance_dirty_pages(struct address_space *mapping);
 void balance_dirty_pages_ratelimited(struct address_space *mapping);
 int pdflush_operation(void (*fn)(unsigned long), unsigned long arg0);
-int do_writepages(struct address_space *mapping, int *nr_to_write);
+int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
 
 /* pdflush.c */
 extern int nr_pdflush_threads;	/* Global so it can be exported to sysctl