md: Relax minimum size restrictions on chunk_size.

Currently, the 'chunk_size' of an array must be at-least PAGE_SIZE.

This makes moving an array to a machine with a larger PAGE_SIZE, or
changing the kernel to use a larger PAGE_SIZE, can stop an array from
working.

For RAID10 and RAID4/5/6, this is non-trivial to fix as the resync
process works on whole pages at a time, and assumes them to be wholly
within a stripe.  For other raid personalities, this restriction is
not needed at all and can be dropped.

So remove the test on chunk_size from common can, and add it in just
the places where it is needed: raid10 and raid4/5/6.

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

1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index d72be4b89e64..a36a7435edf5 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -4007,6 +4007,13 @@ static int run(mddev_t *mddev)
                 return -EIO;
         }
 
+        if (mddev->chunk_size < PAGE_SIZE) {
+                printk(KERN_ERR "md/raid5: chunk_size must be at least "
+                       "PAGE_SIZE but %d < %ld\n",
+                       mddev->chunk_size, PAGE_SIZE);
+                return -EINVAL;
+        }
+
         if (mddev->reshape_position != MaxSector) {
                 /* Check that we can continue the reshape.
                  * Currently only disks can change, it must