linux-kernel - Re: [PATCH 1/2] f2fs: flush pending checkpoints when freezing super

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Message-ID: <YwaD7mJpMLhEm5wd@google.com>
Date:   Wed, 24 Aug 2022 13:02:54 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [PATCH 1/2] f2fs: flush pending checkpoints when freezing super

This avoids -EINVAL when trying to freeze f2fs.

Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
---

 Change log from v1:
  - do not check cprc->f2fs_issue_ckpt in f2fs_flush_ckpt_thread

 fs/f2fs/checkpoint.c | 24 ++++++++++++++++++------
 fs/f2fs/f2fs.h       |  1 +
 fs/f2fs/super.c      |  5 ++---
 3 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 7de48e791920..7bf1feb5ac78 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -1893,15 +1893,27 @@ int f2fs_start_ckpt_thread(struct f2fs_sb_info *sbi)
 void f2fs_stop_ckpt_thread(struct f2fs_sb_info *sbi)
 {
 	struct ckpt_req_control *cprc = &sbi->cprc_info;
+	struct task_struct *ckpt_task;
 
-	if (cprc->f2fs_issue_ckpt) {
-		struct task_struct *ckpt_task = cprc->f2fs_issue_ckpt;
+	if (!cprc->f2fs_issue_ckpt)
+		return;
 
-		cprc->f2fs_issue_ckpt = NULL;
-		kthread_stop(ckpt_task);
+	ckpt_task = cprc->f2fs_issue_ckpt;
+	cprc->f2fs_issue_ckpt = NULL;
+	kthread_stop(ckpt_task);
 
-		flush_remained_ckpt_reqs(sbi, NULL);
-	}
+	f2fs_flush_ckpt_thread(sbi);
+}
+
+void f2fs_flush_ckpt_thread(struct f2fs_sb_info *sbi)
+{
+	struct ckpt_req_control *cprc = &sbi->cprc_info;
+
+	flush_remained_ckpt_reqs(sbi, NULL);
+
+	/* Let's wait for the previous dispatched checkpoint. */
+	while (atomic_read(&cprc->queued_ckpt))
+		io_schedule_timeout(DEFAULT_IO_TIMEOUT);
 }
 
 void f2fs_init_ckpt_req_control(struct f2fs_sb_info *sbi)
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 6770210aae70..088c3d1574b8 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -3711,6 +3711,7 @@ static inline bool f2fs_need_rand_seg(struct f2fs_sb_info *sbi)
  * checkpoint.c
  */
 void f2fs_stop_checkpoint(struct f2fs_sb_info *sbi, bool end_io);
+void f2fs_flush_ckpt_thread(struct f2fs_sb_info *sbi);
 struct page *f2fs_grab_meta_page(struct f2fs_sb_info *sbi, pgoff_t index);
 struct page *f2fs_get_meta_page(struct f2fs_sb_info *sbi, pgoff_t index);
 struct page *f2fs_get_meta_page_retry(struct f2fs_sb_info *sbi, pgoff_t index);
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index e910f0e39d76..4f2ff50b247c 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1671,9 +1671,8 @@ static int f2fs_freeze(struct super_block *sb)
 	if (is_sbi_flag_set(F2FS_SB(sb), SBI_IS_DIRTY))
 		return -EINVAL;
 
-	/* ensure no checkpoint required */
-	if (!llist_empty(&F2FS_SB(sb)->cprc_info.issue_list))
-		return -EINVAL;
+	/* Let's flush checkpoints and stop the thread. */
+	f2fs_flush_ckpt_thread(F2FS_SB(sb));
 
 	/* to avoid deadlock on f2fs_evict_inode->SB_FREEZE_FS */
 	set_sbi_flag(F2FS_SB(sb), SBI_IS_FREEZING);
-- 
2.37.1.595.g718a3a8f04-goog