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>

fs/f2fs/checkpoint.c

@@ -1254,7 +1254,6 @@ int write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 		f2fs_bug_on(sbi, prefree_segments(sbi));
 		flush_sit_entries(sbi, cpc);
 		clear_prefree_segments(sbi, cpc);
-		f2fs_wait_all_discard_bio(sbi);
 		unblock_operations(sbi);
 		goto out;
 	}
@@ -1273,12 +1272,10 @@ int write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 
 	/* unlock all the fs_lock[] in do_checkpoint() */
 	err = do_checkpoint(sbi, cpc);
-	if (err) {
+	if (err)
 		release_discard_addrs(sbi);
-	} else {
+	else
 		clear_prefree_segments(sbi, cpc);
-		f2fs_wait_all_discard_bio(sbi);
-	}
 
 	unblock_operations(sbi);
 	stat_inc_cp_count(sbi->stat_info);

fs/f2fs/f2fs.h

@@ -183,6 +183,8 @@ struct discard_entry {
 
 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 destroy_flush_cmd_control(struct f2fs_sb_info *, bool);
 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);

fs/f2fs/segment.c

@@ -625,20 +625,23 @@ static void locate_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno)
 }
 
 static struct bio_entry *__add_bio_entry(struct f2fs_sb_info *sbi,
-							struct bio *bio)
+			struct bio *bio, block_t lstart, block_t len)
 {
 	struct list_head *wait_list = &(SM_I(sbi)->wait_list);
 	struct bio_entry *be = f2fs_kmem_cache_alloc(bio_entry_slab, GFP_NOFS);
 
 	INIT_LIST_HEAD(&be->list);
 	be->bio = bio;
+	be->lstart = lstart;
+	be->len = len;
 	init_completion(&be->event);
 	list_add_tail(&be->list, wait_list);
 
 	return be;
 }
 
-void f2fs_wait_all_discard_bio(struct f2fs_sb_info *sbi)
+/* This should be covered by global mutex, &sit_i->sentry_lock */
+void f2fs_wait_discard_bio(struct f2fs_sb_info *sbi, block_t blkaddr)
 {
 	struct list_head *wait_list = &(SM_I(sbi)->wait_list);
 	struct bio_entry *be, *tmp;
@@ -647,7 +650,15 @@ void f2fs_wait_all_discard_bio(struct f2fs_sb_info *sbi)
 		struct bio *bio = be->bio;
 		int err;
 
+		if (!completion_done(&be->event)) {
+			if ((be->lstart <= blkaddr &&
+					blkaddr < be->lstart + be->len) ||
+					blkaddr == NULL_ADDR)
 				wait_for_completion_io(&be->event);
+			else
+				continue;
+		}
+
 		err = be->error;
 		if (err == -EOPNOTSUPP)
 			err = 0;
@@ -675,6 +686,7 @@ static int __f2fs_issue_discard_async(struct f2fs_sb_info *sbi,
 		struct block_device *bdev, block_t blkstart, block_t blklen)
 {
 	struct bio *bio = NULL;
+	block_t lblkstart = blkstart;
 	int err;
 
 	trace_f2fs_issue_discard(sbi->sb, blkstart, blklen);
@@ -689,14 +701,14 @@ static int __f2fs_issue_discard_async(struct f2fs_sb_info *sbi,
 				SECTOR_FROM_BLOCK(blklen),
 				GFP_NOFS, 0, &bio);
 	if (!err && bio) {
-		struct bio_entry *be = __add_bio_entry(sbi, bio);
+		struct bio_entry *be = __add_bio_entry(sbi, bio,
+						lblkstart, blklen);
 
 		bio->bi_private = be;
 		bio->bi_end_io = f2fs_submit_bio_wait_endio;
 		bio->bi_opf |= REQ_SYNC;
 		submit_bio(bio);
 	}
-
 	return err;
 }
 
@@ -1575,6 +1587,8 @@ void allocate_data_block(struct f2fs_sb_info *sbi, struct page *page,
 
 	*new_blkaddr = NEXT_FREE_BLKADDR(sbi, curseg);
 
+	f2fs_wait_discard_bio(sbi, *new_blkaddr);
+
 	/*
 	 * __add_sum_entry should be resided under the curseg_mutex
 	 * because, this function updates a summary entry in the

fs/f2fs/super.c

@@ -770,6 +770,9 @@ static void f2fs_put_super(struct super_block *sb)
 		write_checkpoint(sbi, &cpc);
 	}
 
+	/* be sure to wait for any on-going discard commands */
+	f2fs_wait_discard_bio(sbi, NULL_ADDR);
+
 	/* write_checkpoint can update stat informaion */
 	f2fs_destroy_stats(sbi);