[PATCH] md: restart a (raid5) reshape that has been aborted due to a read/write error

An error always aborts any resync/recovery/reshape on the understanding that
it will immediately be restarted if that still makes sense.  However a reshape
currently doesn't get restarted.  With this patch it does.

To avoid restarting when it is not possible to do work, we call into the
personality to check that a reshape is ok, and strengthen raid5_check_reshape
to fail if there are too many failed devices.

We also break some code out into a separate function: remove_and_add_spares as
the indent level for that code was getting crazy.

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>

2 files changed, 47 insertions, 29 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index b5744b1bd2ba..6c06e825cff5 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5357,6 +5357,44 @@ void md_do_sync(mddev_t *mddev)
 EXPORT_SYMBOL_GPL(md_do_sync);
 
 
+static int remove_and_add_spares(mddev_t *mddev)
+{
+        mdk_rdev_t *rdev;
+        struct list_head *rtmp;
+        int spares = 0;
+
+        ITERATE_RDEV(mddev,rdev,rtmp)
+                if (rdev->raid_disk >= 0 &&
+                    (test_bit(Faulty, &rdev->flags) ||
+                     ! test_bit(In_sync, &rdev->flags)) &&
+                    atomic_read(&rdev->nr_pending)==0) {
+                        if (mddev->pers->hot_remove_disk(
+                                    mddev, rdev->raid_disk)==0) {
+                                char nm[20];
+                                sprintf(nm,"rd%d", rdev->raid_disk);
+                                sysfs_remove_link(&mddev->kobj, nm);
+                                rdev->raid_disk = -1;
+                        }
+                }
+
+        if (mddev->degraded) {
+                ITERATE_RDEV(mddev,rdev,rtmp)
+                        if (rdev->raid_disk < 0
+                            && !test_bit(Faulty, &rdev->flags)) {
+                                rdev->recovery_offset = 0;
+                                if (mddev->pers->hot_add_disk(mddev,rdev)) {
+                                        char nm[20];
+                                        sprintf(nm, "rd%d", rdev->raid_disk);
+                                        sysfs_create_link(&mddev->kobj,
+                                                          &rdev->kobj, nm);
+                                        spares++;
+                                        md_new_event(mddev);
+                                } else
+                                        break;
+                        }
+        }
+        return spares;
+}
 /*
  * This routine is regularly called by all per-raid-array threads to
  * deal with generic issues like resync and super-block update.
@@ -5411,7 +5449,7 @@ void md_check_recovery(mddev_t *mddev)
                 return;
 
         if (mddev_trylock(mddev)) {
-                int spares =0;
+                int spares = 0;
 
                 spin_lock_irq(&mddev->write_lock);
                 if (mddev->safemode && !atomic_read(&mddev->writes_pending) &&
@@ -5474,35 +5512,13 @@ void md_check_recovery(mddev_t *mddev)
                  * Spare are also removed and re-added, to allow
                  * the personality to fail the re-add.
                  */
-                ITERATE_RDEV(mddev,rdev,rtmp)
-                        if (rdev->raid_disk >= 0 &&
-                            (test_bit(Faulty, &rdev->flags) || ! test_bit(In_sync, &rdev->flags)) &&
-                            atomic_read(&rdev->nr_pending)==0) {
-                                if (mddev->pers->hot_remove_disk(mddev, rdev->raid_disk)==0) {
-                                        char nm[20];
-                                        sprintf(nm,"rd%d", rdev->raid_disk);
-                                        sysfs_remove_link(&mddev->kobj, nm);
-                                        rdev->raid_disk = -1;
-                                }
-                        }
-
-                if (mddev->degraded) {
-                        ITERATE_RDEV(mddev,rdev,rtmp)
-                                if (rdev->raid_disk < 0
-                                    && !test_bit(Faulty, &rdev->flags)) {
-                                        rdev->recovery_offset = 0;
-                                        if (mddev->pers->hot_add_disk(mddev,rdev)) {
-                                                char nm[20];
-                                                sprintf(nm, "rd%d", rdev->raid_disk);
-                                                sysfs_create_link(&mddev->kobj, &rdev->kobj, nm);
-                                                spares++;
-                                                md_new_event(mddev);
-                                        } else
-                                                break;
-                                }
-                }
 
-                if (spares) {
+                if (mddev->reshape_position != MaxSector) {
+                        if (mddev->pers->check_reshape(mddev) != 0)
+                                /* Cannot proceed */
+                                goto unlock;
+                        set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
+                } else if ((spares = remove_and_add_spares(mddev))) {
                         clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
                         clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
                 } else if (mddev->recovery_cp < MaxSector) {
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 11c3d7bfa797..29fc06b47d4e 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3814,6 +3814,8 @@ static int raid5_check_reshape(mddev_t *mddev)
         if (err)
                 return err;
 
+        if (mddev->degraded > conf->max_degraded)
+                return -EINVAL;
         /* looks like we might be able to manage this */
         return 0;
 }