linux-kernel - [PATCH 5/8] fs,btrfs: Allow kswapd to writeback pages

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Date:	Mon, 19 Jul 2010 14:11:27 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org
Cc:	Dave Chinner <david@...morbit.com>,
	Chris Mason <chris.mason@...cle.com>,
	Nick Piggin <npiggin@...e.de>, Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Christoph Hellwig <hch@...radead.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Mel Gorman <mel@....ul.ie>
Subject: [PATCH 5/8] fs,btrfs: Allow kswapd to writeback pages

As only kswapd and memcg are writing back pages, there should be no
danger of overflowing the stack. Allow the writing back of dirty pages
in btrfs from the VM.

Signed-off-by: Mel Gorman <mel@....ul.ie>
---
 fs/btrfs/disk-io.c |   21 +--------------------
 fs/btrfs/inode.c   |    6 ------
 2 files changed, 1 insertions(+), 26 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 34f7c37..e4aa547 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -696,26 +696,7 @@ static int btree_writepage(struct page *page, struct writeback_control *wbc)
 	int was_dirty;
 
 	tree = &BTRFS_I(page->mapping->host)->io_tree;
-	if (!(current->flags & PF_MEMALLOC)) {
-		return extent_write_full_page(tree, page,
-					      btree_get_extent, wbc);
-	}
-
-	redirty_page_for_writepage(wbc, page);
-	eb = btrfs_find_tree_block(root, page_offset(page),
-				      PAGE_CACHE_SIZE);
-	WARN_ON(!eb);
-
-	was_dirty = test_and_set_bit(EXTENT_BUFFER_DIRTY, &eb->bflags);
-	if (!was_dirty) {
-		spin_lock(&root->fs_info->delalloc_lock);
-		root->fs_info->dirty_metadata_bytes += PAGE_CACHE_SIZE;
-		spin_unlock(&root->fs_info->delalloc_lock);
-	}
-	free_extent_buffer(eb);
-
-	unlock_page(page);
-	return 0;
+	return extent_write_full_page(tree, page, btree_get_extent, wbc);
 }
 
 static int btree_writepages(struct address_space *mapping,
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 1bff92a..5c0e604 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5859,12 +5859,6 @@ static int btrfs_writepage(struct page *page, struct writeback_control *wbc)
 {
 	struct extent_io_tree *tree;
 
-
-	if (current->flags & PF_MEMALLOC) {
-		redirty_page_for_writepage(wbc, page);
-		unlock_page(page);
-		return 0;
-	}
 	tree = &BTRFS_I(page->mapping->host)->io_tree;
 	return extent_write_full_page(tree, page, btrfs_get_extent, wbc);
 }
-- 
1.7.1

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