consolidate generic_writepages and mpage_writepages

Clean up massive code duplication between mpage_writepages() and
generic_writepages().

The new generic function, write_cache_pages() takes a function pointer
argument, which will be called for each page to be written.

Maybe cifs_writepages() too can use this infrastructure, but I'm not
touching that with a ten-foot pole.

The upcoming page writeback support in fuse will also want this.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Acked-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 2 deletions

diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index daa6c125f66e..050915b59576 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -111,9 +111,15 @@ balance_dirty_pages_ratelimited(struct address_space *mapping)
         balance_dirty_pages_ratelimited_nr(mapping, 1);
 }
 
+typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
+                                void *data);
+
 int pdflush_operation(void (*fn)(unsigned long), unsigned long arg0);
-extern int generic_writepages(struct address_space *mapping,
-                              struct writeback_control *wbc);
+int generic_writepages(struct address_space *mapping,
+                       struct writeback_control *wbc);
+int write_cache_pages(struct address_space *mapping,
+                      struct writeback_control *wbc, writepage_t writepage,
+                      void *data);
 int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
 int sync_page_range(struct inode *inode, struct address_space *mapping,
                         loff_t pos, loff_t count);