[PATCH] ext3: Avoid starting a transaction in writepage when not necessary

[Jan Kara]

This does the same as commit 9e80d407736161d9b8b0c5a0d44f786e44c322ea
(avoid starting a transaction when no block allocation is needed)
but for data=writeback mode of ext3. We also cleanup the data=ordered
case a bit to stick to coding style...

Signed-off-by: Jan Kara <jack@xxxxxxx>
---
 fs/ext3/inode.c |   23 ++++++++++++++++++-----
 1 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c
index 4a09ff1..70c86b0 100644
--- a/fs/ext3/inode.c
+++ b/fs/ext3/inode.c
@@ -1512,12 +1512,16 @@ static int ext3_ordered_writepage(struct page *page,
 	if (!page_has_buffers(page)) {
 		create_empty_buffers(page, inode->i_sb->s_blocksize,
 				(1 << BH_Dirty)|(1 << BH_Uptodate));
-	} else if (!walk_page_buffers(NULL, page_buffers(page), 0, PAGE_CACHE_SIZE, NULL, buffer_unmapped)) {
-		/* Provide NULL instead of get_block so that we catch bugs if buffers weren't really mapped */
-		return block_write_full_page(page, NULL, wbc);
+		page_bufs = page_buffers(page);
+	} else {
+		page_bufs = page_buffers(page);
+		if (!walk_page_buffers(NULL, page_bufs, 0, PAGE_CACHE_SIZE,
+				       NULL, buffer_unmapped)) {
+			/* Provide NULL get_block() to catch bugs if buffers
+			 * weren't really mapped */
+			return block_write_full_page(page, NULL, wbc);
+		}
 	}
-	page_bufs = page_buffers(page);
-
 	handle = ext3_journal_start(inode, ext3_writepage_trans_blocks(inode));
 
 	if (IS_ERR(handle)) {
@@ -1572,6 +1576,15 @@ static int ext3_writeback_writepage(struct page *page,
 	if (ext3_journal_current_handle())
 		goto out_fail;
 
+	if (page_has_buffers(page)) {
+		if (!walk_page_buffers(NULL, page_buffers(page), 0,
+				      PAGE_CACHE_SIZE, NULL, buffer_unmapped)) {
+			/* Provide NULL get_block() to catch bugs if buffers
+			 * weren't really mapped */
+			return block_write_full_page(page, NULL, wbc);
+		}
+	}
+
 	handle = ext3_journal_start(inode, ext3_writepage_trans_blocks(inode));
 	if (IS_ERR(handle)) {
 		ret = PTR_ERR(handle);
-- 
1.6.0.2


--liOOAslEiF7prFVr--
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