md/raid5: strengthen check on reshape_position at run.

When reshaping, we work in units of the largest chunk size.
If changing from a larger to a smaller chunk size, that means we
reshape more than one stripe at a time.  So the required alignment
of reshape_position needs to take into account both the old
and new chunk size.

This means that both 'here_new' and 'here_old' are calculated with
respect to the same (maximum) chunk size, so testing if they are the
same when delta_disks is zero becomes pointless.

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

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index a98162f..e95219b 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -6688,6 +6688,8 @@ static int run(struct mddev *mddev)
                sector_t here_new, here_old;
                int old_disks;
                int max_degraded = (mddev->level == 6 ? 2 : 1);
+               int chunk_sectors;
+               int new_data_disks;
 
                if (mddev->new_level != mddev->level) {
                        printk(KERN_ERR "md/raid:%s: unsupported reshape "
@@ -6699,28 +6701,25 @@ static int run(struct mddev *mddev)
                /* reshape_position must be on a new-stripe boundary, and one
                 * further up in new geometry must map after here in old
                 * geometry.
+                * If the chunk sizes are different, then as we perform reshape
+                * in units of the largest of the two, reshape_position needs
+                * be a multiple of the largest chunk size times new data disks.
                 */
                here_new = mddev->reshape_position;
-               if (sector_div(here_new, mddev->new_chunk_sectors *
-                              (mddev->raid_disks - max_degraded))) {
+               chunk_sectors = max(mddev->chunk_sectors, mddev->new_chunk_sectors);
+               new_data_disks = mddev->raid_disks - max_degraded;
+               if (sector_div(here_new, chunk_sectors * new_data_disks)) {
                        printk(KERN_ERR "md/raid:%s: reshape_position not "
                               "on a stripe boundary\n", mdname(mddev));
                        return -EINVAL;
                }
-               reshape_offset = here_new * mddev->new_chunk_sectors;
+               reshape_offset = here_new * chunk_sectors;
                /* here_new is the stripe we will write to */
                here_old = mddev->reshape_position;
-               sector_div(here_old, mddev->chunk_sectors *
-                          (old_disks-max_degraded));
+               sector_div(here_old, chunk_sectors * (old_disks-max_degraded));
                /* here_old is the first stripe that we might need to read
                 * from */
                if (mddev->delta_disks == 0) {
-                       if ((here_new * mddev->new_chunk_sectors !=
-                            here_old * mddev->chunk_sectors)) {
-                               printk(KERN_ERR "md/raid:%s: reshape position is"
-                                      " confused - aborting\n", mdname(mddev));
-                               return -EINVAL;
-                       }
                        /* We cannot be sure it is safe to start an in-place
                         * reshape.  It is only safe if user-space is monitoring
                         * and taking constant backups.
@@ -6739,10 +6738,10 @@ static int run(struct mddev *mddev)
                                return -EINVAL;
                        }
                } else if (mddev->reshape_backwards
-                   ? (here_new * mddev->new_chunk_sectors + min_offset_diff <=
-                      here_old * mddev->chunk_sectors)
-                   : (here_new * mddev->new_chunk_sectors >=
-                      here_old * mddev->chunk_sectors + (-min_offset_diff))) {
+                   ? (here_new * chunk_sectors + min_offset_diff <=
+                      here_old * chunk_sectors)
+                   : (here_new * chunk_sectors >=
+                      here_old * chunk_sectors + (-min_offset_diff))) {
                        /* Reading from the same stripe as writing to - bad */
                        printk(KERN_ERR "md/raid:%s: reshape_position too early for "
                               "auto-recovery - aborting.\n",