From: Jerome Marchand <jmarchan@redhat.com>
Date: Tue, 3 Mar 2009 17:27:26 +0100
Subject: [misc] IO accounting: write accounting
Message-id: 20090303162957.654984299@dhcp-0-152.brq.redhat.com
O-Subject: [RHEL5.4 Patch 04/12] IO accounting: write accounting
Bugzilla: 461636
RH-Acked-by: Jiri Pirko <jpirko@redhat.com>

bz461636

Accounting writes is fairly simple: whenever a process flips a page from clean
to dirty, we accuse it of having caused a write to underlying storage of
PAGE_CACHE_SIZE bytes.

This may overestimate the amount of writing: the page-dirtying may cause only
one buffer_head's worth of writeout.  Fixing that is possible, but probably a
bit messy and isn't obviously important.

Patch is upstream
commit 55e829af06681e5d731c03ba04febbd1c76ca293

diff --git a/fs/buffer.c b/fs/buffer.c
index eb2c148..80c238d 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -35,6 +35,7 @@
 #include <linux/hash.h>
 #include <linux/suspend.h>
 #include <linux/buffer_head.h>
+#include <linux/task_io_accounting_ops.h>
 #include <linux/bio.h>
 #include <linux/notifier.h>
 #include <linux/cpu.h>
@@ -861,8 +862,10 @@ int __set_page_dirty_buffers(struct page *page)
 	if (!TestSetPageDirty(page)) {
 		write_lock_irq(&mapping->tree_lock);
 		if (page->mapping) {	/* Race with truncate? */
-			if (mapping_cap_account_dirty(mapping))
+			if (mapping_cap_account_dirty(mapping)) {
 				__inc_zone_page_state(page, NR_FILE_DIRTY);
+				task_io_account_write(PAGE_CACHE_SIZE);
+			}
 			radix_tree_tag_set(&mapping->page_tree,
 						page_index(page),
 						PAGECACHE_TAG_DIRTY);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index cb415a8..4fa0f54 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -21,6 +21,7 @@
 #include <linux/writeback.h>
 #include <linux/init.h>
 #include <linux/backing-dev.h>
+#include <linux/task_io_accounting_ops.h>
 #include <linux/blkdev.h>
 #include <linux/mpage.h>
 #include <linux/percpu.h>
@@ -636,9 +637,11 @@ int __set_page_dirty_nobuffers(struct page *page)
 			mapping2 = page_mapping(page);
 			if (mapping2) { /* Race with truncate? */
 				BUG_ON(mapping2 != mapping);
-				if (mapping_cap_account_dirty(mapping))
+				if (mapping_cap_account_dirty(mapping)) {
 					__inc_zone_page_state(page,
 								NR_FILE_DIRTY);
+					task_io_account_write(PAGE_CACHE_SIZE);
+				}
 				radix_tree_tag_set(&mapping->page_tree,
 					page_index(page), PAGECACHE_TAG_DIRTY);
 			}