[PATCH v10 20/41] btrfs: extract page adding function

[Naohiro Aota <naohiro.aota@wdc.com>]

This commit extract page adding to bio part from submit_extent_page(). The
page is added only when bio_flags are the same, contiguous and the added
page fits in the same stripe as pages in the bio.

Condition checkings are reordered to allow early return to avoid possibly
heavy btrfs_bio_fits_in_stripe() calling.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
---
 fs/btrfs/extent_io.c | 56 ++++++++++++++++++++++++++++++++------------
 1 file changed, 41 insertions(+), 15 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index e91c504fe973..868ae0874a34 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3012,6 +3012,44 @@ struct bio *btrfs_bio_clone_partial(struct bio *orig, int offset, int size)
 	return bio;
 }
 
+/**
+ * btrfs_bio_add_page	-	attempt to add a page to bio
+ * @bio:	destination bio
+ * @page:	page to add to the bio
+ * @logical:	offset of the new bio or to check whether we are adding
+ *              a contiguous page to the previous one
+ * @pg_offset:	starting offset in the page
+ * @size:	portion of page that we want to write
+ * @prev_bio_flags:  flags of previous bio to see if we can merge the current one
+ * @bio_flags:	flags of the current bio to see if we can merge them
+ *
+ * Attempt to add a page to bio considering stripe alignment etc. Return
+ * true if successfully page added. Otherwise, return false.
+ */
+static bool btrfs_bio_add_page(struct bio *bio, struct page *page, u64 logical,
+			       unsigned int size, unsigned int pg_offset,
+			       unsigned long prev_bio_flags,
+			       unsigned long bio_flags)
+{
+	sector_t sector = logical >> SECTOR_SHIFT;
+	bool contig;
+
+	if (prev_bio_flags != bio_flags)
+		return false;
+
+	if (prev_bio_flags & EXTENT_BIO_COMPRESSED)
+		contig = bio->bi_iter.bi_sector == sector;
+	else
+		contig = bio_end_sector(bio) == sector;
+	if (!contig)
+		return false;
+
+	if (btrfs_bio_fits_in_stripe(page, size, bio, bio_flags))
+		return false;
+
+	return bio_add_page(bio, page, size, pg_offset) == size;
+}
+
 /*
  * @opf:	bio REQ_OP_* and REQ_* flags as one value
  * @wbc:	optional writeback control for io accounting
@@ -3040,27 +3078,15 @@ static int submit_extent_page(unsigned int opf,
 	int ret = 0;
 	struct bio *bio;
 	size_t page_size = min_t(size_t, size, PAGE_SIZE);
-	sector_t sector = offset >> 9;
 	struct extent_io_tree *tree = &BTRFS_I(page->mapping->host)->io_tree;
 
 	ASSERT(bio_ret);
 
 	if (*bio_ret) {
-		bool contig;
-		bool can_merge = true;
-
 		bio = *bio_ret;
-		if (prev_bio_flags & EXTENT_BIO_COMPRESSED)
-			contig = bio->bi_iter.bi_sector == sector;
-		else
-			contig = bio_end_sector(bio) == sector;
-
-		if (btrfs_bio_fits_in_stripe(page, page_size, bio, bio_flags))
-			can_merge = false;
-
-		if (prev_bio_flags != bio_flags || !contig || !can_merge ||
-		    force_bio_submit ||
-		    bio_add_page(bio, page, page_size, pg_offset) < page_size) {
+		if (force_bio_submit ||
+		    !btrfs_bio_add_page(bio, page, offset, page_size, pg_offset,
+					prev_bio_flags, bio_flags)) {
 			ret = submit_one_bio(bio, mirror_num, prev_bio_flags);
 			if (ret < 0) {
 				*bio_ret = NULL;
-- 
2.27.0