f2fs: in prior to issue big discard

Keep issuing big size discard in prior instead of the one with random
size, so that we expect that it will help to:
- be quick to recycle unused large space in flash storage device.
- give a chance for
  a) wait to merge small piece discards into bigger one, or
  b) avoid issuing discards while they have being reallocated by SSR.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index c1faf6d35a8d..d81a365930b5 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -188,6 +188,11 @@ struct discard_entry {
 	unsigned char discard_map[SIT_VBLOCK_MAP_SIZE];	/* segment discard bitmap */
 };
 
+/* max discard pend list number */
+#define MAX_PLIST_NUM		512
+#define plist_idx(blk_num)	((blk_num) >= MAX_PLIST_NUM ?		\
+					(MAX_PLIST_NUM - 1) : (blk_num - 1))
+
 enum {
 	D_PREP,
 	D_SUBMIT,
@@ -221,7 +226,7 @@ struct discard_cmd {
 struct discard_cmd_control {
 	struct task_struct *f2fs_issue_discard;	/* discard thread */
 	struct list_head entry_list;		/* 4KB discard entry list */
-	struct list_head pend_list;		/* store pending entries */
+	struct list_head pend_list[MAX_PLIST_NUM];/* store pending entries */
 	struct list_head wait_list;		/* store on-flushing entries */
 	wait_queue_head_t discard_wait_queue;	/* waiting queue for wake-up */
 	struct mutex cmd_lock;