From: Wu Fengguang <fengguang.wu@intel.com>
Date: Mon, 8 Aug 2011 21:19:47 +0000 (-0600)
Subject: btrfs: fix dirtied pages accounting on sub-page writes
X-Git-Tag: v3.3-rc1~112^2~6
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=32c7f202a4801252a0f3578807b75a961f792870;p=linux.git

btrfs: fix dirtied pages accounting on sub-page writes

When doing 1KB sequential writes to the same page,
balance_dirty_pages_ratelimited_nr() should be called once instead of 4
times, the latter makes the dirtier tasks be throttled much too heavy.

Fix it with proper de-accounting on clear_page_dirty_for_io().

CC: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 97fbe939c050..bfb620ead295 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1136,7 +1136,8 @@ static noinline int prepare_pages(struct btrfs_root *root, struct file *file,
 				     GFP_NOFS);
 	}
 	for (i = 0; i < num_pages; i++) {
-		clear_page_dirty_for_io(pages[i]);
+		if (clear_page_dirty_for_io(pages[i]))
+			account_page_redirty(pages[i]);
 		set_page_extent_mapped(pages[i]);
 		WARN_ON(!PageLocked(pages[i]));
 	}