btrfs: Factor out tree->ops->merge_bio_hook call

In submit_extent_page, there's a visually noisy if statement that, in
the midst of other conditions, does the tree dependency for tree->ops
and tree->ops->merge_bio_hook before calling it, and then another
condition afterwards. If an error is returned from merge_bio_hook,
there's no way to catch it. It's considered a routine "1" return
value instead of a failure.

This patch factors out the dependency check into a new local merge_bio
routine and BUG's on an error. The if statement is less noisy as a side-
effect.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>

1 files changed, 14 insertions, 3 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index a4a7a18..c342e92 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2429,6 +2429,19 @@ static int submit_one_bio(int rw, struct bio *bio, int mirror_num,
 	return ret;
 }
 
+static int merge_bio(struct extent_io_tree *tree, struct page *page,
+		     unsigned long offset, size_t size, struct bio *bio,
+		     unsigned long bio_flags)
+{
+	int ret = 0;
+	if (tree->ops && tree->ops->merge_bio_hook)
+		ret = tree->ops->merge_bio_hook(page, offset, size, bio,
+						bio_flags);
+	BUG_ON(ret < 0);
+	return ret;
+
+}
+
 static int submit_extent_page(int rw, struct extent_io_tree *tree,
 			      struct page *page, sector_t sector,
 			      size_t size, unsigned long offset,
@@ -2457,9 +2470,7 @@ static int submit_extent_page(int rw, struct extent_io_tree *tree,
 				sector;
 
 		if (prev_bio_flags != bio_flags || !contig ||
-		    (tree->ops && tree->ops->merge_bio_hook &&
-		     tree->ops->merge_bio_hook(page, offset, page_size, bio,
-					       bio_flags)) ||
+		    merge_bio(tree, page, offset, page_size, bio, bio_flags) ||
 		    bio_add_page(bio, page, page_size, offset) < page_size) {
 			ret = submit_one_bio(rw, bio, mirror_num,
 					     prev_bio_flags);