dm raid: fix failed takeover/reshapes by keeping raid set frozen

Superblock updates where bogus causing some takovers/reshapes to fail.

Introduce new runtime flag (RT_FLAG_KEEP_RS_FROZEN) to keep a raid set
frozen when a layout change was requested.  Userpace will immediately
reload the table w/o the flags requesting such change once they made it
to the superblocks and any change of recovery/reshape offsets has to be
avoided until after read.

Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 7df4508..8d48651 100644 (file)
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -190,6 +190,7 @@ struct raid_dev {
 #define RT_FLAG_RS_BITMAP_LOADED       2
 #define RT_FLAG_UPDATE_SBS             3
 #define RT_FLAG_RESHAPE_RS             4
+#define RT_FLAG_KEEP_RS_FROZEN         5
 
 /* Array elements of 64 bit needed for rebuild/write_mostly bits */
 #define DISKS_ARRAY_ELEMS ((MAX_RAID_DEVICES + (sizeof(uint64_t) * 8 - 1)) / sizeof(uint64_t) / 8)
@@ -2727,6 +2728,7 @@ static int raid_ctr(struct dm_target *ti, unsigned argc, char **argv)
                        return r;
 
                set_bit(RT_FLAG_UPDATE_SBS, &rs->runtime_flags);
+               set_bit(RT_FLAG_KEEP_RS_FROZEN, &rs->runtime_flags);
                rs_set_new(rs);
        } else if (rs_reshape_requested(rs)) {
                if (rs_is_reshaping(rs)) {
@@ -2767,13 +2769,19 @@ static int raid_ctr(struct dm_target *ti, unsigned argc, char **argv)
                 *           Would cause allocations in raid1->check_reshape
                 *           though, thus more issues with potential failures
                 */
-               else if (rs_is_raid1(rs))
+               else if (rs_is_raid1(rs)) {
+                       set_bit(RT_FLAG_KEEP_RS_FROZEN, &rs->runtime_flags);
                        rs->md.raid_disks = rs->raid_disks;
+               }
+
+               if (test_bit(RT_FLAG_RESHAPE_RS, &rs->runtime_flags)) {
+                       set_bit(RT_FLAG_UPDATE_SBS, &rs->runtime_flags);
+                       set_bit(RT_FLAG_KEEP_RS_FROZEN, &rs->runtime_flags);
+               }
 
                if (rs->md.raid_disks < rs->raid_disks)
                        set_bit(MD_ARRAY_FIRST_USE, &rs->md.flags);
 
-               set_bit(RT_FLAG_UPDATE_SBS, &rs->runtime_flags);
                rs_set_cur(rs);
        } else
                rs_set_cur(rs);
@@ -3231,9 +3239,11 @@ static void raid_postsuspend(struct dm_target *ti)
 {
        struct raid_set *rs = ti->private;
 
-       mddev_suspend(&rs->md);
-       rs->md.ro = 1;
-       clear_bit(RT_FLAG_RS_RESUMED, &rs->runtime_flags);
+       if (test_and_clear_bit(RT_FLAG_RS_RESUMED, &rs->runtime_flags)) {
+               if (!rs->md.suspended)
+                       mddev_suspend(&rs->md);
+               rs->md.ro = 1;
+       }
 }
 
 static void attempt_restore_of_faulty_devices(struct raid_set *rs)
@@ -3308,6 +3318,18 @@ static int __load_dirty_region_bitmap(struct raid_set *rs)
        return r;
 }
 
+/* Enforce updating all superblocks */
+static void rs_update_sbs(struct raid_set *rs)
+{
+       struct mddev *mddev = &rs->md;
+       int ro = mddev->ro;
+
+       set_bit(MD_CHANGE_DEVS, &mddev->flags);
+       mddev->ro = 0;
+       md_update_sb(mddev, 1);
+       mddev->ro = ro;
+}
+
 /*
  * Reshape changes raid algorithm of @rs to new one within personality
  * (e.g. raid6_zr -> raid6_nc), changes stripe size, adds/removes
@@ -3356,9 +3378,12 @@ static int rs_start_reshape(struct raid_set *rs)
        if (!mddev->suspended)
                mddev_suspend(mddev);
 
-       mddev->ro = 0;
-       md_update_sb(mddev, 1);
-       mddev->ro = 1;
+       /*
+        * Now reshape got set up, update superblocks to
+        * reflect the fact so that a table reload will
+        * access proper superblock content in the ctr.
+        */
+       rs_update_sbs(rs);
 
        return 0;
 }
@@ -3375,22 +3400,12 @@ static int raid_preresume(struct dm_target *ti)
 
        /*
         * The superblocks need to be updated on disk if the
-        * array is new or __load_dirty_region_bitmap will overwrite them
-        * in core with old data.
-        *
-        * In case the array got modified (takeover/reshape/resize)
-        * or the data offsets on the component devices changed, they
-        * have to be updated as well.
-        *
-        * Have to switch to readwrite and back in order to
-        * allow for the superblock updates.
+        * array is new or new devices got added (thus zeroed
+        * out by userspace) or __load_dirty_region_bitmap
+        * will overwrite them in core with old data or fail.
         */
-       if (test_and_clear_bit(RT_FLAG_UPDATE_SBS, &rs->runtime_flags)) {
-               set_bit(MD_CHANGE_DEVS, &mddev->flags);
-               mddev->ro = 0;
-               md_update_sb(mddev, 1);
-               mddev->ro = 1;
-       }
+       if (test_bit(RT_FLAG_UPDATE_SBS, &rs->runtime_flags))
+               rs_update_sbs(rs);
 
        /*
         * Disable/enable discard support on raid set after any
@@ -3449,14 +3464,26 @@ static void raid_resume(struct dm_target *ti)
                 * devices are reachable again.
                 */
                attempt_restore_of_faulty_devices(rs);
-       }
+       } else {
+               mddev->ro = 0;
+               mddev->in_sync = 0;
 
-       mddev->ro = 0;
-       mddev->in_sync = 0;
-       clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
+               /*
+                * When passing in flags to the ctr, we expect userspace
+                * to reset them because they made it to the superblocks
+                * and reload the mapping anyway.
+                *
+                * -> only unfreeze recovery in case of a table reload or
+                *    we'll have a bogus recovery/reshape position
+                *    retrieved from the superblock by the ctr because
+                *    the ongoing recovery/reshape will change it after read.
+                */
+               if (!test_bit(RT_FLAG_KEEP_RS_FROZEN, &rs->runtime_flags))
+                       clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
 
-       if (mddev->suspended)
-               mddev_resume(mddev);
+               if (mddev->suspended)
+                       mddev_resume(mddev);
+       }
 }
 
 static struct target_type raid_target = {