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, 3 insertions, 2 deletions

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 8bdc9bfc2887..e3794799f308 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -2028,8 +2028,9 @@ static int run(mddev_t *mddev)
         int nc, fc, fo;
         sector_t stride, size;
 
-        if (mddev->chunk_size == 0) {
-                printk(KERN_ERR "md/raid10: non-zero chunk size required.\n");
+        if (mddev->chunk_size < PAGE_SIZE) {
+                printk(KERN_ERR "md/raid10: chunk size must be "
+                       "at least PAGE_SIZE(%ld).\n", PAGE_SIZE);
                 return -EINVAL;
         }