[PATCH 3/8] md: raid5: use refcount_t for reference counting instead atomic_t

From: Sebastian Andrzej Siewior
Date: Wed May 09 2018 - 15:40:05 EST

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refcount_t type and corresponding API should be used instead of atomic_t when
the variable is used as a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free situations.

Most changes are 1:1 replacements except for
BUG_ON(atomic_inc_return(&sh->count) != 1);

which has been turned into
refcount_inc(&sh->count);
BUG_ON(refcount_read(&sh->count) != 1);

Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
drivers/md/raid5-cache.c | 8 ++---
drivers/md/raid5-ppl.c | 2 +-
drivers/md/raid5.c | 67 ++++++++++++++++++++--------------------
drivers/md/raid5.h | 4 +--
4 files changed, 41 insertions(+), 40 deletions(-)

diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 3c65f52b68f5..532fdf56c117 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -1049,7 +1049,7 @@ int r5l_write_stripe(struct r5l_log *log, struct stripe_head *sh)
* don't delay.
*/
clear_bit(STRIPE_DELAYED, &sh->state);
- atomic_inc(&sh->count);
+ refcount_inc(&sh->count);

mutex_lock(&log->io_mutex);
/* meta + data */
@@ -1388,7 +1388,7 @@ static void r5c_flush_stripe(struct r5conf *conf, struct stripe_head *sh)
lockdep_assert_held(&conf->device_lock);

list_del_init(&sh->lru);
- atomic_inc(&sh->count);
+ refcount_inc(&sh->count);

set_bit(STRIPE_HANDLE, &sh->state);
atomic_inc(&conf->active_stripes);
@@ -1491,7 +1491,7 @@ static void r5c_do_reclaim(struct r5conf *conf)
*/
if (!list_empty(&sh->lru) &&
!test_bit(STRIPE_HANDLE, &sh->state) &&
- atomic_read(&sh->count) == 0) {
+ refcount_read(&sh->count) == 0) {
r5c_flush_stripe(conf, sh);
if (count++ >= R5C_RECLAIM_STRIPE_GROUP)
break;
@@ -2912,7 +2912,7 @@ int r5c_cache_data(struct r5l_log *log, struct stripe_head *sh)
* don't delay.
*/
clear_bit(STRIPE_DELAYED, &sh->state);
- atomic_inc(&sh->count);
+ refcount_inc(&sh->count);

mutex_lock(&log->io_mutex);
/* meta + data */
diff --git a/drivers/md/raid5-ppl.c b/drivers/md/raid5-ppl.c
index 42890a08375b..87840cfe7a80 100644
--- a/drivers/md/raid5-ppl.c
+++ b/drivers/md/raid5-ppl.c
@@ -388,7 +388,7 @@ int ppl_write_stripe(struct r5conf *conf, struct stripe_head *sh)

set_bit(STRIPE_LOG_TRAPPED, &sh->state);
clear_bit(STRIPE_DELAYED, &sh->state);
- atomic_inc(&sh->count);
+ refcount_inc(&sh->count);

if (ppl_log_stripe(log, sh)) {
spin_lock_irq(&ppl_conf->no_mem_stripes_lock);
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index be117d0a65a8..57ea0ae8c7ff 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -306,7 +306,7 @@ static void do_release_stripe(struct r5conf *conf, struct stripe_head *sh,
static void __release_stripe(struct r5conf *conf, struct stripe_head *sh,
struct list_head *temp_inactive_list)
{
- if (atomic_dec_and_test(&sh->count))
+ if (refcount_dec_and_test(&sh->count))
do_release_stripe(conf, sh, temp_inactive_list);
}

@@ -398,7 +398,7 @@ void raid5_release_stripe(struct stripe_head *sh)

/* Avoid release_list until the last reference.
*/
- if (atomic_add_unless(&sh->count, -1, 1))
+ if (refcount_dec_not_one(&sh->count))
return;

if (unlikely(!conf->mddev->thread) ||
@@ -411,7 +411,7 @@ void raid5_release_stripe(struct stripe_head *sh)
slow_path:
local_irq_save(flags);
/* we are ok here if STRIPE_ON_RELEASE_LIST is set or not */
- if (atomic_dec_and_lock(&sh->count, &conf->device_lock)) {
+ if (refcount_dec_and_lock(&sh->count, &conf->device_lock)) {
INIT_LIST_HEAD(&list);
hash = sh->hash_lock_index;
do_release_stripe(conf, sh, &list);
@@ -501,7 +501,7 @@ static void init_stripe(struct stripe_head *sh, sector_t sector, int previous)
struct r5conf *conf = sh->raid_conf;
int i, seq;

- BUG_ON(atomic_read(&sh->count) != 0);
+ BUG_ON(refcount_read(&sh->count) != 0);
BUG_ON(test_bit(STRIPE_HANDLE, &sh->state));
BUG_ON(stripe_operations_active(sh));
BUG_ON(sh->batch_head);
@@ -678,11 +678,11 @@ raid5_get_active_stripe(struct r5conf *conf, sector_t sector,
&conf->cache_state);
} else {
init_stripe(sh, sector, previous);
- atomic_inc(&sh->count);
+ refcount_inc(&sh->count);
}
- } else if (!atomic_inc_not_zero(&sh->count)) {
+ } else if (!refcount_inc_not_zero(&sh->count)) {
spin_lock(&conf->device_lock);
- if (!atomic_read(&sh->count)) {
+ if (!refcount_read(&sh->count)) {
if (!test_bit(STRIPE_HANDLE, &sh->state))
atomic_inc(&conf->active_stripes);
BUG_ON(list_empty(&sh->lru) &&
@@ -698,7 +698,7 @@ raid5_get_active_stripe(struct r5conf *conf, sector_t sector,
sh->group = NULL;
}
}
- atomic_inc(&sh->count);
+ refcount_inc(&sh->count);
spin_unlock(&conf->device_lock);
}
} while (sh == NULL);
@@ -760,9 +760,9 @@ static void stripe_add_to_batch_list(struct r5conf *conf, struct stripe_head *sh
hash = stripe_hash_locks_hash(head_sector);
spin_lock_irq(conf->hash_locks + hash);
head = __find_stripe(conf, head_sector, conf->generation);
- if (head && !atomic_inc_not_zero(&head->count)) {
+ if (head && !refcount_inc_not_zero(&head->count)) {
spin_lock(&conf->device_lock);
- if (!atomic_read(&head->count)) {
+ if (!refcount_read(&head->count)) {
if (!test_bit(STRIPE_HANDLE, &head->state))
atomic_inc(&conf->active_stripes);
BUG_ON(list_empty(&head->lru) &&
@@ -778,7 +778,7 @@ static void stripe_add_to_batch_list(struct r5conf *conf, struct stripe_head *sh
head->group = NULL;
}
}
- atomic_inc(&head->count);
+ refcount_inc(&head->count);
spin_unlock(&conf->device_lock);
}
spin_unlock_irq(conf->hash_locks + hash);
@@ -847,7 +847,7 @@ static void stripe_add_to_batch_list(struct r5conf *conf, struct stripe_head *sh
sh->batch_head->bm_seq = seq;
}

- atomic_inc(&sh->count);
+ refcount_inc(&sh->count);
unlock_out:
unlock_two_stripes(head, sh);
out:
@@ -1110,9 +1110,9 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
pr_debug("%s: for %llu schedule op %d on disc %d\n",
__func__, (unsigned long long)sh->sector,
bi->bi_opf, i);
- atomic_inc(&sh->count);
+ refcount_inc(&sh->count);
if (sh != head_sh)
- atomic_inc(&head_sh->count);
+ refcount_inc(&head_sh->count);
if (use_new_offset(conf, sh))
bi->bi_iter.bi_sector = (sh->sector
+ rdev->new_data_offset);
@@ -1174,9 +1174,9 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
"replacement disc %d\n",
__func__, (unsigned long long)sh->sector,
rbi->bi_opf, i);
- atomic_inc(&sh->count);
+ refcount_inc(&sh->count);
if (sh != head_sh)
- atomic_inc(&head_sh->count);
+ refcount_inc(&head_sh->count);
if (use_new_offset(conf, sh))
rbi->bi_iter.bi_sector = (sh->sector
+ rrdev->new_data_offset);
@@ -1354,7 +1354,7 @@ static void ops_run_biofill(struct stripe_head *sh)
}
}

- atomic_inc(&sh->count);
+ refcount_inc(&sh->count);
init_async_submit(&submit, ASYNC_TX_ACK, tx, ops_complete_biofill, sh, NULL);
async_trigger_callback(&submit);
}
@@ -1432,7 +1432,7 @@ ops_run_compute5(struct stripe_head *sh, struct raid5_percpu *percpu)
if (i != target)
xor_srcs[count++] = sh->dev[i].page;

- atomic_inc(&sh->count);
+ refcount_inc(&sh->count);

init_async_submit(&submit, ASYNC_TX_FENCE|ASYNC_TX_XOR_ZERO_DST, NULL,
ops_complete_compute, sh, to_addr_conv(sh, percpu, 0));
@@ -1521,7 +1521,7 @@ ops_run_compute6_1(struct stripe_head *sh, struct raid5_percpu *percpu)
BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
dest = tgt->page;

- atomic_inc(&sh->count);
+ refcount_inc(&sh->count);

if (target == qd_idx) {
count = set_syndrome_sources(blocks, sh, SYNDROME_SRC_ALL);
@@ -1596,7 +1596,7 @@ ops_run_compute6_2(struct stripe_head *sh, struct raid5_percpu *percpu)
pr_debug("%s: stripe: %llu faila: %d failb: %d\n",
__func__, (unsigned long long)sh->sector, faila, failb);

- atomic_inc(&sh->count);
+ refcount_inc(&sh->count);

if (failb == syndrome_disks+1) {
/* Q disk is one of the missing disks */
@@ -1867,7 +1867,7 @@ ops_run_reconstruct5(struct stripe_head *sh, struct raid5_percpu *percpu,
break;
}
if (i >= sh->disks) {
- atomic_inc(&sh->count);
+ refcount_inc(&sh->count);
set_bit(R5_Discard, &sh->dev[pd_idx].flags);
ops_complete_reconstruct(sh);
return;
@@ -1908,7 +1908,7 @@ ops_run_reconstruct5(struct stripe_head *sh, struct raid5_percpu *percpu,
flags = ASYNC_TX_ACK |
(prexor ? ASYNC_TX_XOR_DROP_DST : ASYNC_TX_XOR_ZERO_DST);

- atomic_inc(&head_sh->count);
+ refcount_inc(&head_sh->count);
init_async_submit(&submit, flags, tx, ops_complete_reconstruct, head_sh,
to_addr_conv(sh, percpu, j));
} else {
@@ -1950,7 +1950,7 @@ ops_run_reconstruct6(struct stripe_head *sh, struct raid5_percpu *percpu,
break;
}
if (i >= sh->disks) {
- atomic_inc(&sh->count);
+ refcount_inc(&sh->count);
set_bit(R5_Discard, &sh->dev[sh->pd_idx].flags);
set_bit(R5_Discard, &sh->dev[sh->qd_idx].flags);
ops_complete_reconstruct(sh);
@@ -1974,7 +1974,7 @@ ops_run_reconstruct6(struct stripe_head *sh, struct raid5_percpu *percpu,
struct stripe_head, batch_list) == head_sh;

if (last_stripe) {
- atomic_inc(&head_sh->count);
+ refcount_inc(&head_sh->count);
init_async_submit(&submit, txflags, tx, ops_complete_reconstruct,
head_sh, to_addr_conv(sh, percpu, j));
} else
@@ -2031,7 +2031,7 @@ static void ops_run_check_p(struct stripe_head *sh, struct raid5_percpu *percpu)
tx = async_xor_val(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
&sh->ops.zero_sum_result, &submit);

- atomic_inc(&sh->count);
+ refcount_inc(&sh->count);
init_async_submit(&submit, ASYNC_TX_ACK, tx, ops_complete_check, sh, NULL);
tx = async_trigger_callback(&submit);
}
@@ -2050,7 +2050,7 @@ static void ops_run_check_pq(struct stripe_head *sh, struct raid5_percpu *percpu
if (!checkp)
srcs[count] = NULL;

- atomic_inc(&sh->count);
+ refcount_inc(&sh->count);
init_async_submit(&submit, ASYNC_TX_ACK, NULL, ops_complete_check,
sh, to_addr_conv(sh, percpu, 0));
async_syndrome_val(srcs, 0, count+2, STRIPE_SIZE,
@@ -2150,7 +2150,7 @@ static struct stripe_head *alloc_stripe(struct kmem_cache *sc, gfp_t gfp,
INIT_LIST_HEAD(&sh->lru);
INIT_LIST_HEAD(&sh->r5c);
INIT_LIST_HEAD(&sh->log_list);
- atomic_set(&sh->count, 1);
+ refcount_set(&sh->count, 1);
sh->raid_conf = conf;
sh->log_start = MaxSector;
for (i = 0; i < disks; i++) {
@@ -2451,7 +2451,7 @@ static int drop_one_stripe(struct r5conf *conf)
spin_unlock_irq(conf->hash_locks + hash);
if (!sh)
return 0;
- BUG_ON(atomic_read(&sh->count));
+ BUG_ON(refcount_read(&sh->count));
shrink_buffers(sh);
free_stripe(conf->slab_cache, sh);
atomic_dec(&conf->active_stripes);
@@ -2483,7 +2483,7 @@ static void raid5_end_read_request(struct bio * bi)
break;

pr_debug("end_read_request %llu/%d, count: %d, error %d.\n",
- (unsigned long long)sh->sector, i, atomic_read(&sh->count),
+ (unsigned long long)sh->sector, i, refcount_read(&sh->count),
bi->bi_status);
if (i == disks) {
bio_reset(bi);
@@ -2620,7 +2620,7 @@ static void raid5_end_write_request(struct bio *bi)
}
}
pr_debug("end_write_request %llu/%d, count %d, error: %d.\n",
- (unsigned long long)sh->sector, i, atomic_read(&sh->count),
+ (unsigned long long)sh->sector, i, refcount_read(&sh->count),
bi->bi_status);
if (i == disks) {
bio_reset(bi);
@@ -4687,7 +4687,7 @@ static void handle_stripe(struct stripe_head *sh)
pr_debug("handling stripe %llu, state=%#lx cnt=%d, "
"pd_idx=%d, qd_idx=%d\n, check:%d, reconstruct:%d\n",
(unsigned long long)sh->sector, sh->state,
- atomic_read(&sh->count), sh->pd_idx, sh->qd_idx,
+ refcount_read(&sh->count), sh->pd_idx, sh->qd_idx,
sh->check_state, sh->reconstruct_state);

analyse_stripe(sh, &s);
@@ -5062,7 +5062,7 @@ static void activate_bit_delay(struct r5conf *conf,
struct stripe_head *sh = list_entry(head.next, struct stripe_head, lru);
int hash;
list_del_init(&sh->lru);
- atomic_inc(&sh->count);
+ refcount_inc(&sh->count);
hash = sh->hash_lock_index;
__release_stripe(conf, sh, &temp_inactive_list[hash]);
}
@@ -5387,7 +5387,8 @@ static struct stripe_head *__get_priority_stripe(struct r5conf *conf, int group)
sh->group = NULL;
}
list_del_init(&sh->lru);
- BUG_ON(atomic_inc_return(&sh->count) != 1);
+ refcount_inc(&sh->count);
+ BUG_ON(refcount_read(&sh->count) != 1);
return sh;
}

diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 3f8da26032ac..bc2a24e99346 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -4,7 +4,7 @@

#include <linux/raid/xor.h>
#include <linux/dmaengine.h>
-
+#include <linux/refcount.h>
/*
*
* Each stripe contains one buffer per device. Each buffer can be in
@@ -208,7 +208,7 @@ struct stripe_head {
short ddf_layout;/* use DDF ordering to calculate Q */
short hash_lock_index;
unsigned long state; /* state flags */
- atomic_t count; /* nr of active thread/requests */
+ refcount_t count; /* nr of active thread/requests */
int bm_seq; /* sequence number for bitmap flushes */
int disks; /* disks in stripe */
int overwrite_disks; /* total overwrite disks in stripe,
--
2.17.0

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