md: expose the degraded status of an assembled array through sysfs

The 'degraded' attribute is useful to quickly determine if the array is
degraded, instead of parsing 'mdadm -D' output or relying on the other
techniques (number of working devices against number of defined devices,
etc.).  The md code already keeps track of this attribute, so it's useful to
export it.

Signed-off-by: Iustin Pop <iusty@k1024.org>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 510625e3a965b26b59ef66a5578441f44ece1f8e..c059ae6f37e5ae1fe789e3fad66ad0a91da3a264 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2833,6 +2833,12 @@ sync_max_store(mddev_t *mddev, const char *buf, size_t len)
 static struct md_sysfs_entry md_sync_max =
 __ATTR(sync_speed_max, S_IRUGO|S_IWUSR, sync_max_show, sync_max_store);
 
+static ssize_t
+degraded_show(mddev_t *mddev, char *page)
+{
+       return sprintf(page, "%d\n", mddev->degraded);
+}
+static struct md_sysfs_entry md_degraded = __ATTR_RO(degraded);
 
 static ssize_t
 sync_speed_show(mddev_t *mddev, char *page)
@@ -2976,6 +2982,7 @@ static struct attribute *md_redundancy_attrs[] = {
        &md_suspend_lo.attr,
        &md_suspend_hi.attr,
        &md_bitmap.attr,
+       &md_degraded.attr,
        NULL,
 };
 static struct attribute_group md_redundancy_group = {