monitor: read_and_act: handle race conditions for resync_start

[thirdparty/mdadm.git] / monitor.c

diff --git a/monitor.c b/monitor.c
index 3cb421409ffd0105e550865f2287941c9577a797..60c5d5a286eb1b3a5210def0f0532edc7c2c4bff 100644 (file)
--- a/monitor.c
+++ b/monitor.c
@@ -75,18 +75,21 @@ static int read_attr(char *buf, int len, int fd)
        return n;
 }
 
-static unsigned long long read_resync_start(int fd)
+static void read_resync_start(int fd, unsigned long long *v)
 {
        char buf[30];
        int n;
 
        n = read_attr(buf, 30, fd);
-       if (n <= 0)
-               return 0;
+       if (n <= 0) {
+               dprintf("%s: Failed to read resync_start (%d)\n",
+                       __func__, fd);
+               return;
+       }
        if (strncmp(buf, "none", 4) == 0)
-               return MaxSector;
+               *v = MaxSector;
        else
-               return strtoull(buf, NULL, 10);
+               *v = strtoull(buf, NULL, 10);
 }
 
 static unsigned long long read_sync_completed(int fd)
@@ -237,13 +240,20 @@ static int read_and_act(struct active_array *a)
 
        a->curr_state = read_state(a->info.state_fd);
        a->curr_action = read_action(a->action_fd);
-       a->info.resync_start = read_resync_start(a->resync_start_fd);
+       if (a->curr_state != clear)
+               /*
+                * In "clear" state, resync_start may wrongly be set to "0"
+                * when the kernel called md_clean but didn't remove the
+                * sysfs attributes yet
+                */
+               read_resync_start(a->resync_start_fd, &a->info.resync_start);
        sync_completed = read_sync_completed(a->sync_completed_fd);
        for (mdi = a->info.devs; mdi ; mdi = mdi->next) {
                mdi->next_state = 0;
                mdi->curr_state = 0;
                if (mdi->state_fd >= 0) {
-                       mdi->recovery_start = read_resync_start(mdi->recovery_fd);
+                       read_resync_start(mdi->recovery_fd,
+                                         &mdi->recovery_start);
                        mdi->curr_state = read_dev_state(mdi->state_fd);
                }
        }