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:edbe83ab4c
("md/raid5: allow the stripe_cache to grow and shrink.") Cc: stable@vger.kernel.org (4.1 - please release with2d5b569b66
) Reported-by: Tomas Papan <tomas.papan@gmail.com> Signed-off-by: NeilBrown <neilb@suse.com>
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49895bcc7e
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@ -2256,7 +2256,7 @@ static int resize_stripes(struct r5conf *conf, int newsize)
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static int drop_one_stripe(struct r5conf *conf)
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{
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struct stripe_head *sh;
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int hash = (conf->max_nr_stripes - 1) % NR_STRIPE_HASH_LOCKS;
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int hash = (conf->max_nr_stripes - 1) & STRIPE_HASH_LOCKS_MASK;
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spin_lock_irq(conf->hash_locks + hash);
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sh = get_free_stripe(conf, hash);
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@ -6388,7 +6388,8 @@ static unsigned long raid5_cache_scan(struct shrinker *shrink,
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if (mutex_trylock(&conf->cache_size_mutex)) {
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ret= 0;
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while (ret < sc->nr_to_scan) {
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while (ret < sc->nr_to_scan &&
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conf->max_nr_stripes > conf->min_nr_stripes) {
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if (drop_one_stripe(conf) == 0) {
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ret = SHRINK_STOP;
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break;
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