f2fs: avoid small data writes by skipping writepages

This patch introduces nr_pages_to_skip(sbi, type) to determine writepages can
be skipped.
The dentry, node, and meta pages can be conrolled by F2FS without breaking the
FS consistency.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index c3d5e3689ffc..bbd976100d14 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -664,3 +664,22 @@ static inline unsigned int max_hw_blocks(struct f2fs_sb_info *sbi)
 	struct request_queue *q = bdev_get_queue(bdev);
 	return SECTOR_TO_BLOCK(sbi, queue_max_sectors(q));
 }
+
+/*
+ * It is very important to gather dirty pages and write at once, so that we can
+ * submit a big bio without interfering other data writes.
+ * By default, 512 pages for directory data,
+ * 512 pages (2MB) * 3 for three types of nodes, and
+ * max_bio_blocks for meta are set.
+ */
+static inline int nr_pages_to_skip(struct f2fs_sb_info *sbi, int type)
+{
+	if (type == DATA)
+		return sbi->blocks_per_seg;
+	else if (type == NODE)
+		return 3 * sbi->blocks_per_seg;
+	else if (type == META)
+		return MAX_BIO_BLOCKS(max_hw_blocks(sbi));
+	else
+		return 0;
+}