2 files changed, 61 insertions, 2 deletions

diff --git a/Documentation/md.txt b/Documentation/md.txt
index 03a13c462cf2..b19978e035fc 100644
--- a/Documentation/md.txt
+++ b/Documentation/md.txt
@@ -207,6 +207,15 @@ All md devices contain:
      available.  It will then appear at md/dev-XXX (depending on the
      name of the device) and further configuration is then possible.
 
+   safe_mode_delay
+     When an md array has seen no write requests for a certain period
+     of time, it will be marked as 'clean'.  When another write
+     request arrive, the array is marked as 'dirty' before the write
+     commenses.  This is known as 'safe_mode'.
+     The 'certain period' is controlled by this file which stores the
+     period as a number of seconds.  The default is 200msec (0.200).
+     Writing a value of 0 disables safemode.
+
    sync_speed_min
    sync_speed_max
      This are similar to /proc/sys/dev/raid/speed_limit_{min,max}
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 30a93d64921e..ad576ad2ca76 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -44,6 +44,7 @@
 #include <linux/suspend.h>
 #include <linux/poll.h>
 #include <linux/mutex.h>
+#include <linux/ctype.h>
 
 #include <linux/init.h>
 
@@ -1978,6 +1979,54 @@ static void analyze_sbs(mddev_t * mddev)
 }
 
 static ssize_t
+safe_delay_show(mddev_t *mddev, char *page)
+{
+        int msec = (mddev->safemode_delay*1000)/HZ;
+        return sprintf(page, "%d.%03d\n", msec/1000, msec%1000);
+}
+static ssize_t
+safe_delay_store(mddev_t *mddev, const char *cbuf, size_t len)
+{
+        int scale=1;
+        int dot=0;
+        int i;
+        unsigned long msec;
+        char buf[30];
+        char *e;
+        /* remove a period, and count digits after it */
+        if (len >= sizeof(buf))
+                return -EINVAL;
+        strlcpy(buf, cbuf, len);
+        buf[len] = 0;
+        for (i=0; i<len; i++) {
+                if (dot) {
+                        if (isdigit(buf[i])) {
+                                buf[i-1] = buf[i];
+                                scale *= 10;
+                        }
+                        buf[i] = 0;
+                } else if (buf[i] == '.') {
+                        dot=1;
+                        buf[i] = 0;
+                }
+        }
+        msec = simple_strtoul(buf, &e, 10);
+        if (e == buf || (*e && *e != '\n'))
+                return -EINVAL;
+        msec = (msec * 1000) / scale;
+        if (msec == 0)
+                mddev->safemode_delay = 0;
+        else {
+                mddev->safemode_delay = (msec*HZ)/1000;
+                if (mddev->safemode_delay == 0)
+                        mddev->safemode_delay = 1;
+        }
+        return len;
+}
+static struct md_sysfs_entry md_safe_delay =
+__ATTR(safe_mode_delay, 0644,safe_delay_show, safe_delay_store);
+
+static ssize_t
 level_show(mddev_t *mddev, char *page)
 {
         struct mdk_personality *p = mddev->pers;
@@ -2433,6 +2482,7 @@ static struct attribute *md_default_attrs[] = {
         &md_size.attr,
         &md_metadata.attr,
         &md_new_device.attr,
+        &md_safe_delay.attr,
         NULL,
 };
 
@@ -2708,7 +2758,7 @@ static int do_md_run(mddev_t * mddev)
         mddev->safemode = 0;
         mddev->safemode_timer.function = md_safemode_timeout;
         mddev->safemode_timer.data = (unsigned long) mddev;
-        mddev->safemode_delay = (20 * HZ)/1000 +1; /* 20 msec delay */
+        mddev->safemode_delay = (200 * HZ)/1000 +1; /* 200 msec delay */
         mddev->in_sync = 1;
 
         ITERATE_RDEV(mddev,rdev,tmp)
@@ -4594,7 +4644,7 @@ void md_write_end(mddev_t *mddev)
         if (atomic_dec_and_test(&mddev->writes_pending)) {
                 if (mddev->safemode == 2)
                         md_wakeup_thread(mddev->thread);
-                else
+                else if (mddev->safemode_delay)
                         mod_timer(&mddev->safemode_timer, jiffies + mddev->safemode_delay);
         }
 }