f2fs: avoid IO split due to mixed WB_SYNC_ALL and WB_SYNC_NONE
If two threads try to flush dirty pages in different inodes respectively,
f2fs_write_data_pages() will produce WRITE and WRITE_SYNC one at a time,
resulting in a lot of 4KB seperated IOs.
So, this patch gives higher priority to WB_SYNC_ALL IOs and gathers write
IOs with a big WRITE_SYNC'ed bio.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 8f36080..b1cac6d 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1605,8 +1605,10 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
last_idx = page->index;
}
- if (--wbc->nr_to_write <= 0 &&
- wbc->sync_mode == WB_SYNC_NONE) {
+ /* give a priority to WB_SYNC threads */
+ if ((atomic_read(&F2FS_M_SB(mapping)->wb_sync_req) ||
+ --wbc->nr_to_write <= 0) &&
+ wbc->sync_mode == WB_SYNC_NONE) {
done = 1;
break;
}
@@ -1662,9 +1664,18 @@ static int f2fs_write_data_pages(struct address_space *mapping,
trace_f2fs_writepages(mapping->host, wbc, DATA);
+ /* to avoid spliting IOs due to mixed WB_SYNC_ALL and WB_SYNC_NONE */
+ if (wbc->sync_mode == WB_SYNC_ALL)
+ atomic_inc(&sbi->wb_sync_req);
+ else if (atomic_read(&sbi->wb_sync_req))
+ goto skip_write;
+
blk_start_plug(&plug);
ret = f2fs_write_cache_pages(mapping, wbc);
blk_finish_plug(&plug);
+
+ if (wbc->sync_mode == WB_SYNC_ALL)
+ atomic_dec(&sbi->wb_sync_req);
/*
* if some pages were truncated, we cannot guarantee its mapping->host
* to detect pending bios.