[PATCH 05/27] btrfs: avoid duplicate balance_dirty_pages_ratelimited() calls

[Wu Fengguang]

When doing 1KB sequential writes to the same page,
balance_dirty_pages_ratelimited() should be called once instead of 4
times. Failing to do so will make all tasks throttled much too heavy.

CC: Chris Mason <chris.mason@xxxxxxxxxx>
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
 fs/btrfs/file.c       |   11 +++++++----
 fs/btrfs/ioctl.c      |    6 ++++--
 fs/btrfs/relocation.c |    6 ++++--
 3 files changed, 15 insertions(+), 8 deletions(-)

--- linux-next.orig/fs/btrfs/file.c	2011-02-21 14:24:56.000000000 +0800
+++ linux-next/fs/btrfs/file.c	2011-02-21 14:37:34.000000000 +0800
@@ -770,7 +770,8 @@ out:
 static noinline int prepare_pages(struct btrfs_root *root, struct file *file,
 			 struct page **pages, size_t num_pages,
 			 loff_t pos, unsigned long first_index,
-			 unsigned long last_index, size_t write_bytes)
+			 unsigned long last_index, size_t write_bytes,
+			 int *nr_dirtied)
 {
 	struct extent_state *cached_state = NULL;
 	int i;
@@ -837,7 +838,8 @@ again:
 				     GFP_NOFS);
 	}
 	for (i = 0; i < num_pages; i++) {
-		clear_page_dirty_for_io(pages[i]);
+		if (!clear_page_dirty_for_io(pages[i]))
+			(*nr_dirtied)++;
 		set_page_extent_mapped(pages[i]);
 		WARN_ON(!PageLocked(pages[i]));
 	}
@@ -989,6 +991,7 @@ static ssize_t btrfs_file_aio_write(stru
 	}
 
 	while (iov_iter_count(&i) > 0) {
+		int nr_dirtied = 0;
 		size_t offset = pos & (PAGE_CACHE_SIZE - 1);
 		size_t write_bytes = min(iov_iter_count(&i),
 					 nrptrs * (size_t)PAGE_CACHE_SIZE -
@@ -1015,7 +1018,7 @@ static ssize_t btrfs_file_aio_write(stru
 
 		ret = prepare_pages(root, file, pages, num_pages,
 				    pos, first_index, last_index,
-				    write_bytes);
+				    write_bytes, &nr_dirtied);
 		if (ret) {
 			btrfs_delalloc_release_space(inode,
 					num_pages << PAGE_CACHE_SHIFT);
@@ -1050,7 +1053,7 @@ static ssize_t btrfs_file_aio_write(stru
 			} else {
 				balance_dirty_pages_ratelimited_nr(
 							inode->i_mapping,
-							dirty_pages);
+							nr_dirtied);
 				if (dirty_pages <
 				(root->leafsize >> PAGE_CACHE_SHIFT) + 1)
 					btrfs_btree_balance_dirty(root, 1);
--- linux-next.orig/fs/btrfs/ioctl.c	2011-02-21 14:24:56.000000000 +0800
+++ linux-next/fs/btrfs/ioctl.c	2011-02-21 14:26:21.000000000 +0800
@@ -654,6 +654,7 @@ static int btrfs_defrag_file(struct file
 	u64 skip = 0;
 	u64 defrag_end = 0;
 	unsigned long i;
+	int dirtied;
 	int ret;
 	int compress_type = BTRFS_COMPRESS_ZLIB;
 
@@ -766,7 +767,7 @@ again:
 
 		btrfs_set_extent_delalloc(inode, page_start, page_end, NULL);
 		ClearPageChecked(page);
-		set_page_dirty(page);
+		dirtied = set_page_dirty(page);
 		unlock_extent(io_tree, page_start, page_end, GFP_NOFS);
 
 loop_unlock:
@@ -774,7 +775,8 @@ loop_unlock:
 		page_cache_release(page);
 		mutex_unlock(&inode->i_mutex);
 
-		balance_dirty_pages_ratelimited_nr(inode->i_mapping, 1);
+		if (dirtied)
+			balance_dirty_pages_ratelimited_nr(inode->i_mapping, 1);
 		i++;
 	}
 
--- linux-next.orig/fs/btrfs/relocation.c	2011-02-21 14:24:56.000000000 +0800
+++ linux-next/fs/btrfs/relocation.c	2011-02-21 14:26:21.000000000 +0800
@@ -2902,6 +2902,7 @@ static int relocate_file_extent_cluster(
 	struct file_ra_state *ra;
 	int nr = 0;
 	int ret = 0;
+	int dirtied;
 
 	if (!cluster->nr)
 		return 0;
@@ -2978,7 +2979,7 @@ static int relocate_file_extent_cluster(
 		}
 
 		btrfs_set_extent_delalloc(inode, page_start, page_end, NULL);
-		set_page_dirty(page);
+		dirtied = set_page_dirty(page);
 
 		unlock_extent(&BTRFS_I(inode)->io_tree,
 			      page_start, page_end, GFP_NOFS);
@@ -2986,7 +2987,8 @@ static int relocate_file_extent_cluster(
 		page_cache_release(page);
 
 		index++;
-		balance_dirty_pages_ratelimited(inode->i_mapping);
+		if (dirtied)
+			balance_dirty_pages_ratelimited(inode->i_mapping);
 		btrfs_throttle(BTRFS_I(inode)->root);
 	}
 	WARN_ON(nr != cluster->nr);


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