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 bec00b201a73..83eb78b00137 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)
 {