1 files changed, 75 insertions, 4 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index ab40529bdabe..d29215d966da 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4823,11 +4823,40 @@ static raid5_conf_t *setup_conf(mddev_t *mddev)
                 return ERR_PTR(-ENOMEM);
 }
 
+
+static int only_parity(int raid_disk, int algo, int raid_disks, int max_degraded)
+{
+        switch (algo) {
+        case ALGORITHM_PARITY_0:
+                if (raid_disk < max_degraded)
+                        return 1;
+                break;
+        case ALGORITHM_PARITY_N:
+                if (raid_disk >= raid_disks - max_degraded)
+                        return 1;
+                break;
+        case ALGORITHM_PARITY_0_6:
+                if (raid_disk == 0 || 
+                    raid_disk == raid_disks - 1)
+                        return 1;
+                break;
+        case ALGORITHM_LEFT_ASYMMETRIC_6:
+        case ALGORITHM_RIGHT_ASYMMETRIC_6:
+        case ALGORITHM_LEFT_SYMMETRIC_6:
+        case ALGORITHM_RIGHT_SYMMETRIC_6:
+                if (raid_disk == raid_disks - 1)
+                        return 1;
+        }
+        return 0;
+}
+
 static int run(mddev_t *mddev)
 {
         raid5_conf_t *conf;
         int working_disks = 0, chunk_size;
+        int dirty_parity_disks = 0;
         mdk_rdev_t *rdev;
+        sector_t reshape_offset = 0;
 
         if (mddev->recovery_cp != MaxSector)
                 printk(KERN_NOTICE "raid5: %s is not clean"
@@ -4861,6 +4890,7 @@ static int run(mddev_t *mddev)
                                "on a stripe boundary\n");
                         return -EINVAL;
                 }
+                reshape_offset = here_new * mddev->new_chunk_sectors;
                 /* here_new is the stripe we will write to */
                 here_old = mddev->reshape_position;
                 sector_div(here_old, mddev->chunk_sectors *
@@ -4916,10 +4946,51 @@ static int run(mddev_t *mddev)
         /*
          * 0 for a fully functional array, 1 or 2 for a degraded array.
          */
-        list_for_each_entry(rdev, &mddev->disks, same_set)
-                if (rdev->raid_disk >= 0 &&
-                    test_bit(In_sync, &rdev->flags))
+        list_for_each_entry(rdev, &mddev->disks, same_set) {
+                if (rdev->raid_disk < 0)
+                        continue;
+                if (test_bit(In_sync, &rdev->flags))
                         working_disks++;
+                /* This disc is not fully in-sync.  However if it
+                 * just stored parity (beyond the recovery_offset),
+                 * when we don't need to be concerned about the
+                 * array being dirty.
+                 * When reshape goes 'backwards', we never have
+                 * partially completed devices, so we only need
+                 * to worry about reshape going forwards.
+                 */
+                /* Hack because v0.91 doesn't store recovery_offset properly. */
+                if (mddev->major_version == 0 &&
+                    mddev->minor_version > 90)
+                        rdev->recovery_offset = reshape_offset;
+                        
+                printk("%d: w=%d pa=%d pr=%d m=%d a=%d r=%d op1=%d op2=%d\n",
+                       rdev->raid_disk, working_disks, conf->prev_algo,
+                       conf->previous_raid_disks, conf->max_degraded,
+                       conf->algorithm, conf->raid_disks, 
+                       only_parity(rdev->raid_disk,
+                                   conf->prev_algo,
+                                   conf->previous_raid_disks,
+                                   conf->max_degraded),
+                       only_parity(rdev->raid_disk,
+                                   conf->algorithm,
+                                   conf->raid_disks,
+                                   conf->max_degraded));
+                if (rdev->recovery_offset < reshape_offset) {
+                        /* We need to check old and new layout */
+                        if (!only_parity(rdev->raid_disk,
+                                         conf->algorithm,
+                                         conf->raid_disks,
+                                         conf->max_degraded))
+                                continue;
+                }
+                if (!only_parity(rdev->raid_disk,
+                                 conf->prev_algo,
+                                 conf->previous_raid_disks,
+                                 conf->max_degraded))
+                        continue;
+                dirty_parity_disks++;
+        }
 
         mddev->degraded = (max(conf->raid_disks, conf->previous_raid_disks)
                            - working_disks);
@@ -4935,7 +5006,7 @@ static int run(mddev_t *mddev)
         mddev->dev_sectors &= ~(mddev->chunk_sectors - 1);
         mddev->resync_max_sectors = mddev->dev_sectors;
 
-        if (mddev->degraded > 0 &&
+        if (mddev->degraded > dirty_parity_disks &&
             mddev->recovery_cp != MaxSector) {
                 if (mddev->ok_start_degraded)
                         printk(KERN_WARNING