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Commit 49895bcc authored by NeilBrown's avatar NeilBrown
Browse files

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: edbe83ab ("md/raid5: allow the stripe_cache to grow and shrink.")
Cc: stable@vger.kernel.org (4.1 - please release with 2d5b569b)
Reported-by: default avatarTomas Papan <tomas.papan@gmail.com>
Signed-off-by: default avatarNeilBrown <neilb@suse.com>
parent b6878d9e

drivers/md/raid5.c

+3 −2
Original line number Diff line number Diff line
@@ -2256,7 +2256,7 @@ static int resize_stripes(struct r5conf *conf, int newsize) 
static int drop_one_stripe(struct r5conf *conf)

{

	struct stripe_head *sh;

	int hash = (conf->max_nr_stripes - 1) % NR_STRIPE_HASH_LOCKS;

	int hash = (conf->max_nr_stripes - 1) & STRIPE_HASH_LOCKS_MASK;



	spin_lock_irq(conf->hash_locks + hash);

	sh = get_free_stripe(conf, hash);
@@ -6388,7 +6388,8 @@ static unsigned long raid5_cache_scan(struct shrinker *shrink, 


	if (mutex_trylock(&conf->cache_size_mutex)) {

		ret= 0;

		while (ret < sc->nr_to_scan) {

		while (ret < sc->nr_to_scan &&

		       conf->max_nr_stripes > conf->min_nr_stripes) {

			if (drop_one_stripe(conf) == 0) {

				ret = SHRINK_STOP;

				break;