f2fs: relax async discard commands more

This patch relaxes async discard commands to avoid waiting its end_io during
checkpoint.
Instead of waiting them during checkpoint, it will be done when actually reusing
them.

Test on initial partition of nvme drive.

 # time fstrim /mnt/test

Before : 6.158s
After : 4.822s

Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index bdcfe2a..e0db895f 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -183,6 +183,8 @@
 
 struct bio_entry {
 	struct list_head list;
+	block_t lstart;
+	block_t len;
 	struct bio *bio;
 	struct completion event;
 	int error;
@@ -2111,7 +2113,7 @@
 void invalidate_blocks(struct f2fs_sb_info *, block_t);
 bool is_checkpointed_data(struct f2fs_sb_info *, block_t);
 void refresh_sit_entry(struct f2fs_sb_info *, block_t, block_t);
-void f2fs_wait_all_discard_bio(struct f2fs_sb_info *);
+void f2fs_wait_discard_bio(struct f2fs_sb_info *, block_t);
 void clear_prefree_segments(struct f2fs_sb_info *, struct cp_control *);
 void release_discard_addrs(struct f2fs_sb_info *);
 int npages_for_summary_flush(struct f2fs_sb_info *, bool);