f2fs: modify the number of issued pages to merge IOs

When testing f2fs on an SSD, I found some 128 page IOs followed by 1 page IO
were issued by f2fs_write_node_pages.
This means that there were some mishandling flows which degrades performance.

Previous f2fs_write_node_pages determines the number of pages to be written,
nr_to_write, as follows.

1. The bio_get_nr_vecs returns 129 pages.
2. The bio_alloc makes a room for 128 pages.
3. The initial 128 pages go into one bio.
4. The existing bio is submitted, and a new bio is prepared for the last 1 page.
5. Finally, sync_node_pages submits the last 1 page bio.

The problem is from the use of bio_get_nr_vecs, so this patch replace it
with max_hw_blocks using queue_max_sectors.

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

1 files changed, 2 insertions, 4 deletions

diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index f14eb7b8b2c4..7209d637f942 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1171,7 +1171,6 @@ static int f2fs_write_node_pages(struct address_space *mapping,
                             struct writeback_control *wbc)
 {
         struct f2fs_sb_info *sbi = F2FS_SB(mapping->host->i_sb);
-        struct block_device *bdev = sbi->sb->s_bdev;
         long nr_to_write = wbc->nr_to_write;
 
         /* First check balancing cached NAT entries */
@@ -1185,10 +1184,9 @@ static int f2fs_write_node_pages(struct address_space *mapping,
                 return 0;
 
         /* if mounting is failed, skip writing node pages */
-        wbc->nr_to_write = bio_get_nr_vecs(bdev);
+        wbc->nr_to_write = max_hw_blocks(sbi);
         sync_node_pages(sbi, 0, wbc);
-        wbc->nr_to_write = nr_to_write -
-                (bio_get_nr_vecs(bdev) - wbc->nr_to_write);
+        wbc->nr_to_write = nr_to_write - (max_hw_blocks(sbi) - wbc->nr_to_write);
         return 0;
 }