f2fs: avoid writing node/metapages during writes

Let's keep more node/meta pages in run time.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/segment.h

@@ -715,9 +715,9 @@ 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;
+		return 8 * sbi->blocks_per_seg;
 	else if (type == META)
-		return MAX_BIO_BLOCKS(sbi);
+		return 8 * MAX_BIO_BLOCKS(sbi);
 	else
 		return 0;
 }
@@ -736,7 +736,7 @@ static inline long nr_pages_to_write(struct f2fs_sb_info *sbi, int type,
 	nr_to_write = wbc->nr_to_write;
 
 	if (type == NODE)
-		desired = 3 * max_hw_blocks(sbi);
+		desired = 2 * max_hw_blocks(sbi);
 	else
 		desired = MAX_BIO_BLOCKS(sbi);