[PATCH] Btrfs: remove repeated eb->pages check in, disk-io.c/csum_dirty_buffer

[PATCH] Btrfs: remove repeated eb->pages check in, disk-io.c/csum_dirty_buffer

[Wang Sheng-Hui]

In csum_dirty_buffer, we first get eb from page->private.
Then we check if the page is the first page of eb. Later
we check it again. Remove the repeated check here.

Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>
---
 fs/btrfs/disk-io.c |    8 +++-----
 1 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 22e98e0..8919c56 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -432,14 +432,12 @@ static int csum_dirty_buffer(struct btrfs_root *root, struct page *page)
 	tree = &BTRFS_I(page->mapping->host)->io_tree;

 	eb = (struct extent_buffer *)page->private;
-	if (page != eb->pages[0])
-		return 0;
-	found_start = btrfs_header_bytenr(eb);
-	if (found_start != start) {
+	if (page != eb->pages[0]) {
 		WARN_ON(1);
 		return 0;
 	}
-	if (eb->pages[0] != page) {
+	found_start = btrfs_header_bytenr(eb);
+	if (found_start != start) {
 		WARN_ON(1);
 		return 0;
 	}
-- 
1.7.5.4

Re: [PATCH] Btrfs: remove repeated eb->pages check in, disk-io.c/csum_dirty_buffer

[Chris Mason]

On Mon, Oct 08, 2012 at 07:26:15AM -0600, Wang Sheng-Hui wrote:
> In csum_dirty_buffer, we first get eb from page->private.
> Then we check if the page is the first page of eb. Later
> we check it again. Remove the repeated check here.

You had the right idea here, two checks and one has a warning, so you
kept the warning.  But when the metadata block size is bigger than a
page, the WARN_ON triggers for any page that isn't the first one in the
extent buffer.

I kept this commit but removed the WARN_ON(1)

-chris