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From:   Ye Bin <yebin10@huawei.com>
To:     <tytso@mit.edu>, <adilger.kernel@dilger.ca>,
        <linux-ext4@vger.kernel.org>
CC:     <linux-kernel@vger.kernel.org>, <jack@suse.cz>,
        Ye Bin <yebin10@huawei.com>
Subject: [PATCH -next v2 2/6] ext4: introduce last_check_time record previous check time
Date:   Sat, 11 Sep 2021 17:00:55 +0800
Message-ID: <20210911090059.1876456-3-yebin10@huawei.com>
In-Reply-To: <20210911090059.1876456-1-yebin10@huawei.com>
References: <20210911090059.1876456-1-yebin10@huawei.com>
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kmmpd:
...
    diff = jiffies - last_update_time;
    if (diff > mmp_check_interval * HZ) {
...
As "mmp_check_interval = 2 * mmp_update_interval", 'diff' always little
than 'mmp_update_interval', so there will never trigger detection.
Introduce last_check_time record previous check time.

Signed-off-by: Ye Bin <yebin10@huawei.com>
---
 fs/ext4/mmp.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c
index 12af6dc8457b..c781b09a78c9 100644
--- a/fs/ext4/mmp.c
+++ b/fs/ext4/mmp.c
@@ -152,6 +152,7 @@ static int kmmpd(void *data)
 	int mmp_update_interval = le16_to_cpu(es->s_mmp_update_interval);
 	unsigned mmp_check_interval;
 	unsigned long last_update_time;
+	unsigned long last_check_time;
 	unsigned long diff;
 	int retval = 0;
 
@@ -170,6 +171,7 @@ static int kmmpd(void *data)
 
 	memcpy(mmp->mmp_nodename, init_utsname()->nodename,
 	       sizeof(mmp->mmp_nodename));
+	last_check_time = jiffies;
 
 	while (!kthread_should_stop() && !sb_rdonly(sb)) {
 		if (!ext4_has_feature_mmp(sb)) {
@@ -198,17 +200,18 @@ static int kmmpd(void *data)
 		}
 
 		diff = jiffies - last_update_time;
-		if (diff < mmp_update_interval * HZ)
+		if (diff < mmp_update_interval * HZ) {
 			schedule_timeout_interruptible(mmp_update_interval *
 						       HZ - diff);
+			diff = jiffies - last_update_time;
+		}
 
 		/*
 		 * We need to make sure that more than mmp_check_interval
-		 * seconds have not passed since writing. If that has happened
-		 * we need to check if the MMP block is as we left it.
+		 * seconds have not passed since check. If that has happened
+		 * we need to check if the MMP block is as we write it.
 		 */
-		diff = jiffies - last_update_time;
-		if (diff > mmp_check_interval * HZ) {
+		if (jiffies - last_check_time > mmp_check_interval * HZ) {
 			struct buffer_head *bh_check = NULL;
 			struct mmp_struct *mmp_check;
 
@@ -234,6 +237,7 @@ static int kmmpd(void *data)
 				goto wait_to_exit;
 			}
 			put_bh(bh_check);
+			last_check_time = jiffies;
 		}
 
 		 /*
-- 
2.31.1