md/raid5: Allow recovered part of partially recovered devices to be in-sync

During a recovery of reshape the early part of some devices might be
in-sync while the later parts are not.
We we know we are looking at an early part it is good to treat that
part as in-sync for stripe calculations.

This is particularly important for a reshape which suffers device
failure.  Treating the data as in-sync can mean the difference between
data-safety and data-loss.

Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index d4b233c..09f07da 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3031,7 +3031,6 @@ static void handle_stripe5(struct stripe_head *sh)
                mdk_rdev_t *rdev;
 
                dev = &sh->dev[i];
-               clear_bit(R5_Insync, &dev->flags);
 
                pr_debug("check %d: state 0x%lx toread %p read %p write %p "
                        "written %p\n", i, dev->flags, dev->toread, dev->read,
@@ -3068,17 +3067,27 @@ static void handle_stripe5(struct stripe_head *sh)
                        blocked_rdev = rdev;
                        atomic_inc(&rdev->nr_pending);
                }
-               if (!rdev || !test_bit(In_sync, &rdev->flags)) {
+               clear_bit(R5_Insync, &dev->flags);
+               if (!rdev)
+                       /* Not in-sync */;
+               else if (test_bit(In_sync, &rdev->flags))
+                       set_bit(R5_Insync, &dev->flags);
+               else {
+                       /* could be in-sync depending on recovery/reshape status */
+                       if (sh->sector + STRIPE_SECTORS <= rdev->recovery_offset)
+                               set_bit(R5_Insync, &dev->flags);
+               }
+               if (!test_bit(R5_Insync, &dev->flags)) {
                        /* The ReadError flag will just be confusing now */
                        clear_bit(R5_ReadError, &dev->flags);
                        clear_bit(R5_ReWrite, &dev->flags);
                }
-               if (!rdev || !test_bit(In_sync, &rdev->flags)
-                   || test_bit(R5_ReadError, &dev->flags)) {
+               if (test_bit(R5_ReadError, &dev->flags))
+                       clear_bit(R5_Insync, &dev->flags);
+               if (!test_bit(R5_Insync, &dev->flags)) {
                        s.failed++;
                        s.failed_num = i;
-               } else
-                       set_bit(R5_Insync, &dev->flags);
+               }
        }
        rcu_read_unlock();
 
@@ -3312,7 +3321,6 @@ static void handle_stripe6(struct stripe_head *sh)
        for (i=disks; i--; ) {
                mdk_rdev_t *rdev;
                dev = &sh->dev[i];
-               clear_bit(R5_Insync, &dev->flags);
 
                pr_debug("check %d: state 0x%lx read %p write %p written %p\n",
                        i, dev->flags, dev->toread, dev->towrite, dev->written);
@@ -3350,18 +3358,28 @@ static void handle_stripe6(struct stripe_head *sh)
                        blocked_rdev = rdev;
                        atomic_inc(&rdev->nr_pending);
                }
-               if (!rdev || !test_bit(In_sync, &rdev->flags)) {
+               clear_bit(R5_Insync, &dev->flags);
+               if (!rdev)
+                       /* Not in-sync */;
+               else if (test_bit(In_sync, &rdev->flags))
+                       set_bit(R5_Insync, &dev->flags);
+               else {
+                       /* in sync if before recovery_offset */
+                       if (sh->sector + STRIPE_SECTORS <= rdev->recovery_offset)
+                               set_bit(R5_Insync, &dev->flags);
+               }
+               if (!test_bit(R5_Insync, &dev->flags)) {
                        /* The ReadError flag will just be confusing now */
                        clear_bit(R5_ReadError, &dev->flags);
                        clear_bit(R5_ReWrite, &dev->flags);
                }
-               if (!rdev || !test_bit(In_sync, &rdev->flags)
-                   || test_bit(R5_ReadError, &dev->flags)) {
+               if (test_bit(R5_ReadError, &dev->flags))
+                       clear_bit(R5_Insync, &dev->flags);
+               if (!test_bit(R5_Insync, &dev->flags)) {
                        if (s.failed < 2)
                                r6s.failed_num[s.failed] = i;
                        s.failed++;
-               } else
-                       set_bit(R5_Insync, &dev->flags);
+               }
        }
        rcu_read_unlock();