md/raid5: don't let shrink_slab shrink too far.
authorNeilBrown <neilb@suse.com>
Mon, 3 Aug 2015 07:09:57 +0000 (17:09 +1000)
committerNeilBrown <neilb@suse.com>
Mon, 3 Aug 2015 07:10:56 +0000 (17:10 +1000)
commit49895bcc7e566ba455eb2996607d6fbd3447ce16
treee62f0eb74f454df5f6e219eba25ca965a591abd2
parentb6878d9e03043695dbf3fa1caa6dfc09db225b16
md/raid5: don't let shrink_slab shrink too far.

I have a report of drop_one_stripe() called from
raid5_cache_scan() apparently finding ->max_nr_stripes == 0.

This should not be allowed.

So add a test to keep max_nr_stripes above min_nr_stripes.

Also use a 'mask' rather than a 'mod' in drop_one_stripe
to ensure 'hash' is valid even if max_nr_stripes does reach zero.

Fixes: edbe83ab4c27 ("md/raid5: allow the stripe_cache to grow and shrink.")
Cc: stable@vger.kernel.org (4.1 - please release with 2d5b569b665)
Reported-by: Tomas Papan <tomas.papan@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.com>
drivers/md/raid5.c