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>

1 files changed, 30 insertions, 12 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index d4b233c25f2e..09f07dadf404 100644
--- 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();