[PATCH v2] f2fs: give another chance to issue discard with current granularity

[Chao Yu]

If discard IOs are blocked by user IO, do not skip to select and issue
discard with lower granularity, retry with current granularity.

Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
---
v2:
- fix deadloop.
 fs/f2fs/segment.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 1f9ae8270f86..6e2b2e717a40 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1191,7 +1191,7 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
 	struct discard_cmd *dc, *tmp;
 	struct blk_plug plug;
 	int i, iter = 0, issued = 0;
-	bool io_interrupted = false;
+	bool io_interrupted = false, end_up = false;
 
 	for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
 		if (i + 1 < dpolicy->granularity)
@@ -1199,6 +1199,7 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
 		pend_list = &dcc->pend_list[i];
 
 		mutex_lock(&dcc->cmd_lock);
+retry:
 		if (list_empty(pend_list))
 			goto next;
 		if (unlikely(dcc->rbtree_check))
@@ -1217,14 +1218,23 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
 			__submit_discard_cmd(sbi, dpolicy, dc);
 			issued++;
 skip:
-			if (++iter >= dpolicy->max_requests)
+			if (++iter >= dpolicy->max_requests) {
+				end_up = true;
 				break;
+			}
 		}
 		blk_finish_plug(&plug);
+
+		/*
+		 * if discard IO was interrupted by user IOs, give another
+		 * chance to issue discard with current granularity.
+		 */
+		if (io_interrupted && !end_up)
+			goto retry;
 next:
 		mutex_unlock(&dcc->cmd_lock);
 
-		if (iter >= dpolicy->max_requests)
+		if (end_up)
 			break;
 	}
 
-- 
2.18.0.rc1