[PATCH] md: fix --re-add for raid1 and raid6

If you have an array with a write-intent-bitmap, and you remove a device, then
re-add it, a full recovery isn't needed.  We detect a re-add by looking at
saved_raid_disk.  For raid1, it doesn't matter which disk it was, only whether
or not it was an active device.  The old code being removed set a value of
'mirror' which was then ignored, so it can go.  The changed code performs the
correct check.

For raid6, if there are two missing devices, make sure we chose the right slot
on --re-add rather than always the first slot.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 2da9d3ba902dd1337ff2d724e46838f9d604f148..3066c587b5391202dda91f8e4a9bdc977a4b335a 100644 (file)
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -953,9 +953,6 @@ static int raid1_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
        int mirror = 0;
        mirror_info_t *p;
 
-       if (rdev->saved_raid_disk >= 0 &&
-           conf->mirrors[rdev->saved_raid_disk].rdev == NULL)
-               mirror = rdev->saved_raid_disk;
        for (mirror=0; mirror < mddev->raid_disks; mirror++)
                if ( !(p=conf->mirrors+mirror)->rdev) {
 
@@ -972,7 +969,10 @@ static int raid1_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
                        p->head_position = 0;
                        rdev->raid_disk = mirror;
                        found = 1;
-                       if (rdev->saved_raid_disk != mirror)
+                       /* As all devices are equivalent, we don't need a full recovery
+                        * if this was recently any drive of the array
+                        */
+                       if (rdev->saved_raid_disk < 0)
                                conf->fullsync = 1;
                        rcu_assign_pointer(p->rdev, rdev);
                        break;

diff --git a/drivers/md/raid6main.c b/drivers/md/raid6main.c
index 00da37848d0556f298763d10690e87b077d0d821..0000d162d198a60d558ab4be3f54f608ff8b7473 100644 (file)
--- a/drivers/md/raid6main.c
+++ b/drivers/md/raid6main.c
@@ -2158,9 +2158,15 @@ static int raid6_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
                /* no point adding a device */
                return 0;
        /*
-        * find the disk ...
+        * find the disk ... but prefer rdev->saved_raid_disk
+        * if possible.
         */
-       for (disk=0; disk < mddev->raid_disks; disk++)
+       if (rdev->saved_raid_disk >= 0 &&
+           conf->disks[rdev->saved_raid_disk].rdev == NULL)
+               disk = rdev->saved_raid_disk;
+       else
+               disk = 0;
+       for ( ; disk < mddev->raid_disks; disk++)
                if ((p=conf->disks + disk)->rdev == NULL) {
                        clear_bit(In_sync, &rdev->flags);
                        rdev->raid_disk = disk;