ext4: use redirty_page_for_writepage() in ext4_bio_write_page()

When we cannot write a page we should use redirty_page_for_writepage()
instead of plain set_page_dirty(). That tells writeback code we have
problems, redirties only the page (redirtying buffers is not needed),
and updates mm accounting of failed page writes.

Also move clearing of buffer dirty flag after io_submit_add_bh(). At that
moment we are sure buffer will be going to disk.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/page-io.c

@@ -23,6 +23,7 @@
 #include <linux/workqueue.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
+#include <linux/mm.h>
 
 #include "ext4_jbd2.h"
 #include "xattr.h"
@@ -434,7 +435,7 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
 
 	io_page = kmem_cache_alloc(io_page_cachep, GFP_NOFS);
 	if (!io_page) {
-		set_page_dirty(page);
+		redirty_page_for_writepage(wbc, page);
 		unlock_page(page);
 		return -ENOMEM;
 	}
@@ -466,17 +467,17 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
 			set_buffer_uptodate(bh);
 			continue;
 		}
-		clear_buffer_dirty(bh);
 		ret = io_submit_add_bh(io, io_page, inode, wbc, bh);
 		if (ret) {
 			/*
 			 * We only get here on ENOMEM.  Not much else
 			 * we can do but mark the page as dirty, and
 			 * better luck next time.
 			 */
-			set_page_dirty(page);
+			redirty_page_for_writepage(wbc, page);
 			break;
 		}
+		clear_buffer_dirty(bh);
 	}
 	unlock_page(page);
 	/*