[PATCH v3] f2fs: fix to freeze GC and discard threads quickly

[Daeho Jeong <daeho43@gmail.com>]

From: Daeho Jeong <daehojeong@google.com>

Suspend can fail if kernel threads do not freeze for a while.
f2fs_gc and f2fs_discard threads can perform long-running operations
that prevent them from reaching a freeze point in a timely manner.

This patch adds explicit freezing checks in the following locations:
1. f2fs_gc: Added a check at the 'retry' label to exit the loop quickly
   if freezing is requested, especially during heavy GC rounds.
2. __issue_discard_cmd: Added a 'suspended' flag to break both inner and
   outer loops during discard command issuance if freezing is detected
   after at least one command has been issued.
3. __issue_discard_cmd_orderly: Added a similar check for orderly discard
   to ensure responsiveness.

These checks ensure that the threads release locks safely and enter the
frozen state.

Signed-off-by: Daeho Jeong <daehojeong@google.com>
---
v3: removed unnecessary suspended check
v2: add freezing check in do_garbage_collect()
---
 fs/f2fs/gc.c      | 10 ++++++++++
 fs/f2fs/segment.c | 12 +++++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 981eac629fe9..f07746a14aa4 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -1883,12 +1883,18 @@ static int do_garbage_collect(struct f2fs_sb_info *sbi,
 				sbi->next_victim_seg[gc_type] =
 					(cur_segno + 1 < sec_end_segno) ?
 					cur_segno + 1 : NULL_SEGNO;
+
+			if (unlikely(freezing(current))) {
+				folio_put_refs(sum_folio, 2);
+				goto stop;
+			}
 		}
 next_block:
 		folio_put_refs(sum_folio, 2);
 		segno = block_end_segno;
 	}
 
+stop:
 	if (submitted)
 		f2fs_submit_merged_write(sbi, data_type);
 
@@ -1962,6 +1968,10 @@ int f2fs_gc(struct f2fs_sb_info *sbi, struct f2fs_gc_control *gc_control)
 		goto stop;
 	}
 retry:
+	if (unlikely(freezing(current))) {
+		ret = 0;
+		goto stop;
+	}
 	ret = __get_victim(sbi, &segno, gc_type, gc_control->one_time);
 	if (ret) {
 		/* allow to search victim from sections has pinned data */
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index e9b6d774b985..0c4fb4270185 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1606,6 +1606,9 @@ static void __issue_discard_cmd_orderly(struct f2fs_sb_info *sbi,
 		if (dc->state != D_PREP)
 			goto next;
 
+		if (*issued > 0 && unlikely(freezing(current)))
+			break;
+
 		if (dpolicy->io_aware && !is_idle(sbi, DISCARD_TIME)) {
 			io_interrupted = true;
 			break;
@@ -1645,6 +1648,7 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
 	struct blk_plug plug;
 	int i, issued;
 	bool io_interrupted = false;
+	bool suspended = false;
 
 	if (dpolicy->timeout)
 		f2fs_update_time(sbi, UMOUNT_DISCARD_TIMEOUT);
@@ -1675,6 +1679,11 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
 		list_for_each_entry_safe(dc, tmp, pend_list, list) {
 			f2fs_bug_on(sbi, dc->state != D_PREP);
 
+			if (issued > 0 && unlikely(freezing(current))) {
+				suspended = true;
+				break;
+			}
+
 			if (dpolicy->timeout &&
 				f2fs_time_over(sbi, UMOUNT_DISCARD_TIMEOUT))
 				break;
@@ -1694,7 +1703,8 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
 next:
 		mutex_unlock(&dcc->cmd_lock);
 
-		if (issued >= dpolicy->max_requests || io_interrupted)
+		if (issued >= dpolicy->max_requests || io_interrupted ||
+					suspended)
 			break;
 	}
 
-- 
2.53.0.880.g73c4285caa-goog