commit c76242c56efb4d799bb15af1035a5f503cb4b8f3
Author: Tomasz Majchrzak <tomasz.majchrzak@intel.com>
Date:   Wed Oct 4 10:18:21 2017 +0200

    mdmon: get safe mode delay file descriptor early
    
    After switch root new mdmon is started. It sends initrd mdmon a signal
    to terminate. initrd mdmon receives it and switches the safe mode delay
    to 1 ms in order to get array to clean state and flush last version of
    metadata. The problem is sysfs filesystem is not available to initrd mdmon
    after switch root so the original safe mode delay is unchanged. The delay
    is set to few seconds - if there is a lot of traffic on the filesystem,
    initrd mdmon doesn't terminate for a long time (no clean state). There
    are 2 instances of mdmon. initrd mdmon flushes metadata when array goes
    to clean state but this metadata might be already outdated.
    
    Use file descriptor obtained on mdmon start to change safe mode delay.
    
    Signed-off-by: Tomasz Majchrzak <tomasz.majchrzak@intel.com>
    Signed-off-by: Jes Sorensen <jsorensen@fb.com>

diff --git a/managemon.c b/managemon.c
index cc3c6f1..4e85398 100644
--- a/managemon.c
+++ b/managemon.c
@@ -129,6 +129,8 @@ static void close_aa(struct active_array *aa)
 		close(aa->metadata_fd);
 	if (aa->sync_completed_fd >= 0)
 		close(aa->sync_completed_fd);
+	if (aa->safe_mode_delay_fd >= 0)
+		close(aa->safe_mode_delay_fd);
 }
 
 static void free_aa(struct active_array *aa)
@@ -532,9 +534,15 @@ static void manage_member(struct mdstat_ent *mdstat,
 	if (a->container == NULL)
 		return;
 
-	if (sigterm && a->info.safe_mode_delay != 1) {
-		sysfs_set_safemode(&a->info, 1);
-		a->info.safe_mode_delay = 1;
+	if (sigterm && a->info.safe_mode_delay != 1 &&
+	    a->safe_mode_delay_fd >= 0) {
+		long int new_delay = 1;
+		char delay[10];
+		ssize_t len;
+
+		len = snprintf(delay, sizeof(delay), "0.%03ld\n", new_delay);
+		if (write(a->safe_mode_delay_fd, delay, len) == len)
+			a->info.safe_mode_delay = new_delay;
 	}
 
 	/* We don't check the array while any update is pending, as it
@@ -734,6 +742,8 @@ static void manage_new(struct mdstat_ent *mdstat,
 	new->resync_start_fd = sysfs_open2(new->info.sys_name, NULL, "resync_start");
 	new->metadata_fd = sysfs_open2(new->info.sys_name, NULL, "metadata_version");
 	new->sync_completed_fd = sysfs_open2(new->info.sys_name, NULL, "sync_completed");
+	new->safe_mode_delay_fd = sysfs_open2(new->info.sys_name, NULL,
+					      "safe_mode_delay");
 
 	dprintf("inst: %s action: %d state: %d\n", inst,
 		new->action_fd, new->info.state_fd);
diff --git a/mdmon.h b/mdmon.h
index 0b08c3d..818367c 100644
--- a/mdmon.h
+++ b/mdmon.h
@@ -35,6 +35,7 @@ struct active_array {
 	int resync_start_fd;
 	int metadata_fd; /* for monitoring rw/ro status */
 	int sync_completed_fd; /* for checkpoint notification events */
+	int safe_mode_delay_fd;
 	unsigned long long last_checkpoint; /* sync_completed fires for many
 					     * reasons this field makes sure the
 					     * kernel has made progress before