[PATCH 003 of 5] md: Expose the degraded status of an assembled array through sysfs

[NeilBrown <neilb@suse.de>]

From: Iustin Pop <iusty@k1024.org>

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>

### Diffstat output
 ./drivers/md/md.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff .prev/drivers/md/md.c ./drivers/md/md.c
--- .prev/drivers/md/md.c	2007-10-15 14:06:32.000000000 +1000
+++ ./drivers/md/md.c	2007-10-15 14:06:52.000000000 +1000
@@ -2833,6 +2833,12 @@ sync_max_store(mddev_t *mddev, const cha
 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_a
 	&md_suspend_lo.attr,
 	&md_suspend_hi.attr,
 	&md_bitmap.attr,
+	&md_degraded.attr,
 	NULL,
 };
 static struct attribute_group md_redundancy_group = {