md: support blocking writes to an array on device failure

Allows a userspace metadata handler to take action upon detecting a device
failure.

Based on an original patch by Neil Brown.

Changes:
-added blocked_wait waitqueue to rdev
-don't qualify Blocked with Faulty always let userspace block writes
-added md_wait_for_blocked_rdev to wait for the block device to be clear, if
 userspace misses the notification another one is sent every 5 seconds
-set MD_RECOVERY_NEEDED after clearing "blocked"
-kill DoBlock flag, just test mddev->external

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
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>

1 files changed, 32 insertions, 1 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index bec00b201a7..83eb78b0013 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1828,6 +1828,10 @@ state_show(mdk_rdev_t *rdev, char *page)
 		len += sprintf(page+len, "%swrite_mostly",sep);
 		sep = ",";
 	}
+	if (test_bit(Blocked, &rdev->flags)) {
+		len += sprintf(page+len, "%sblocked", sep);
+		sep = ",";
+	}
 	if (!test_bit(Faulty, &rdev->flags) &&
 	    !test_bit(In_sync, &rdev->flags)) {
 		len += sprintf(page+len, "%sspare", sep);
@@ -1844,6 +1848,8 @@ state_store(mdk_rdev_t *rdev, const char *buf, size_t len)
 	 *  remove  - disconnects the device
 	 *  writemostly - sets write_mostly
 	 *  -writemostly - clears write_mostly
+	 *  blocked - sets the Blocked flag
+	 *  -blocked - clears the Blocked flag
 	 */
 	int err = -EINVAL;
 	if (cmd_match(buf, "faulty") && rdev->mddev->pers) {
@@ -1866,6 +1872,16 @@ state_store(mdk_rdev_t *rdev, const char *buf, size_t len)
 	} else if (cmd_match(buf, "-writemostly")) {
 		clear_bit(WriteMostly, &rdev->flags);
 		err = 0;
+	} else if (cmd_match(buf, "blocked")) {
+		set_bit(Blocked, &rdev->flags);
+		err = 0;
+	} else if (cmd_match(buf, "-blocked")) {
+		clear_bit(Blocked, &rdev->flags);
+		wake_up(&rdev->blocked_wait);
+		set_bit(MD_RECOVERY_NEEDED, &rdev->mddev->recovery);
+		md_wakeup_thread(rdev->mddev->thread);
+
+		err = 0;
 	}
 	return err ? err : len;
 }
@@ -2194,7 +2210,9 @@ static mdk_rdev_t *md_import_device(dev_t newdev, int super_format, int super_mi
 			goto abort_free;
 		}
 	}
+
 	INIT_LIST_HEAD(&rdev->same_set);
+	init_waitqueue_head(&rdev->blocked_wait);
 
 	return rdev;
 
@@ -4958,6 +4976,9 @@ void md_error(mddev_t *mddev, mdk_rdev_t *rdev)
 
 	if (!rdev || test_bit(Faulty, &rdev->flags))
 		return;
+
+	if (mddev->external)
+		set_bit(Blocked, &rdev->flags);
 /*
 	dprintk("md_error dev:%s, rdev:(%d:%d), (caller: %p,%p,%p,%p).\n",
 		mdname(mddev),
@@ -5760,7 +5781,7 @@ static int remove_and_add_spares(mddev_t *mddev)
 
 	rdev_for_each(rdev, rtmp, mddev)
 		if (rdev->raid_disk >= 0 &&
-		    !mddev->external &&
+		    !test_bit(Blocked, &rdev->flags) &&
 		    (test_bit(Faulty, &rdev->flags) ||
 		     ! test_bit(In_sync, &rdev->flags)) &&
 		    atomic_read(&rdev->nr_pending)==0) {
@@ -5959,6 +5980,16 @@ void md_check_recovery(mddev_t *mddev)
 	}
 }
 
+void md_wait_for_blocked_rdev(mdk_rdev_t *rdev, mddev_t *mddev)
+{
+	sysfs_notify(&rdev->kobj, NULL, "state");
+	wait_event_timeout(rdev->blocked_wait,
+			   !test_bit(Blocked, &rdev->flags),
+			   msecs_to_jiffies(5000));
+	rdev_dec_pending(rdev, mddev);
+}
+EXPORT_SYMBOL(md_wait_for_blocked_rdev);
+
 static int md_notify_reboot(struct notifier_block *this,
 			    unsigned long code, void *x)
 {