4.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: NeilBrown <neilb@xxxxxxxx>
commit 49895bcc7e566ba455eb2996607d6fbd3447ce16 upstream.
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.")
Reported-by: Tomas Papan <tomas.papan@xxxxxxxxx>
Signed-off-by: NeilBrown <neilb@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/raid5.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2245,7 +2245,7 @@ static int resize_stripes(struct r5conf
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);
@@ -6375,7 +6375,8 @@ static unsigned long raid5_cache_scan(st
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;
--
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