Re: [PATCH -next 2/6] ext4: introduce last_check_time record previous check time

On 2021/9/9 10:20, Guoqing Jiang wrote:

On 9/6/21 10:47 PM, Ye Bin wrote:

quoted

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 <redacted>
---
  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..89797f12a815 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_update_time = jiffies;

I'm sorry, actually i want to init 'last_check_time' at here,  I will 
fix it in v2.
Thanks,
YeBin

quoted

        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) {

Before the above checking, seems last_check_time is not initialized yet.

quoted

              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;
          }
             /*

Thanks,
Guoqing
.