John,
On 2018/08/23 10:37, John Pittman wrote:
> The API surrounding refcount_t should be used in place of atomic_t
> when variables are being used as reference counters. This API can
> prevent issues such as counter overflows and use-after-free
> conditions. Within the dm zoned metadata stack, the atomic_t API
> is used for mblk->ref and zone->refcount. Change these to use
> refcount_t, avoiding the issues mentioned.
>
> Signed-off-by: John Pittman <jpittman@xxxxxxxxxx>
> ---
> drivers/md/dm-zoned-metadata.c | 25 +++++++++++++------------
> drivers/md/dm-zoned.h | 2 +-
> 2 files changed, 14 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/md/dm-zoned-metadata.c b/drivers/md/dm-zoned-metadata.c
> index 969954915566..92e635749414 100644
> --- a/drivers/md/dm-zoned-metadata.c
> +++ b/drivers/md/dm-zoned-metadata.c
> @@ -99,7 +99,7 @@ struct dmz_mblock {
> struct rb_node node;
> struct list_head link;
> sector_t no;
> - atomic_t ref;
> + refcount_t ref;
While reviewing your patch, I realized that this ref is always manipulated under
the zmd->mblk_lock spinlock. So there is no need for it to be an atomic or a
refcount. An unsigned int would do as well and be faster. My fault.
I will send a patch to go on top of yours to fix that.
Otherwise:
Reviewed-by: Damien Le Moal <damien.lemoal@xxxxxxx>
Tested-by: Damien Le Moal <damien.lemoal@xxxxxxx>
Thanks !
> unsigned long state;
> struct page *page;
> void *data;
> @@ -296,7 +296,7 @@ static struct dmz_mblock *dmz_alloc_mblock(struct dmz_metadata *zmd,
>
> RB_CLEAR_NODE(&mblk->node);
> INIT_LIST_HEAD(&mblk->link);
> - atomic_set(&mblk->ref, 0);
> + refcount_set(&mblk->ref, 0);
> mblk->state = 0;
> mblk->no = mblk_no;
> mblk->data = page_address(mblk->page);
> @@ -397,7 +397,7 @@ static struct dmz_mblock *dmz_fetch_mblock(struct dmz_metadata *zmd,
> return NULL;
>
> spin_lock(&zmd->mblk_lock);
> - atomic_inc(&mblk->ref);
> + refcount_inc(&mblk->ref);
> set_bit(DMZ_META_READING, &mblk->state);
> dmz_insert_mblock(zmd, mblk);
> spin_unlock(&zmd->mblk_lock);
> @@ -484,7 +484,7 @@ static void dmz_release_mblock(struct dmz_metadata *zmd,
>
> spin_lock(&zmd->mblk_lock);
>
> - if (atomic_dec_and_test(&mblk->ref)) {
> + if (refcount_dec_and_test(&mblk->ref)) {
> if (test_bit(DMZ_META_ERROR, &mblk->state)) {
> rb_erase(&mblk->node, &zmd->mblk_rbtree);
> dmz_free_mblock(zmd, mblk);
> @@ -511,7 +511,8 @@ static struct dmz_mblock *dmz_get_mblock(struct dmz_metadata *zmd,
> mblk = dmz_lookup_mblock(zmd, mblk_no);
> if (mblk) {
> /* Cache hit: remove block from LRU list */
> - if (atomic_inc_return(&mblk->ref) == 1 &&
> + refcount_inc(&mblk->ref);
> + if (refcount_read(&mblk->ref) == 1 &&
> !test_bit(DMZ_META_DIRTY, &mblk->state))
> list_del_init(&mblk->link);
> }
> @@ -753,7 +754,7 @@ int dmz_flush_metadata(struct dmz_metadata *zmd)
>
> spin_lock(&zmd->mblk_lock);
> clear_bit(DMZ_META_DIRTY, &mblk->state);
> - if (atomic_read(&mblk->ref) == 0)
> + if (refcount_read(&mblk->ref) == 0)
> list_add_tail(&mblk->link, &zmd->mblk_lru_list);
> spin_unlock(&zmd->mblk_lock);
> }
> @@ -1048,7 +1049,7 @@ static int dmz_init_zone(struct dmz_metadata *zmd, struct dm_zone *zone,
> }
>
> INIT_LIST_HEAD(&zone->link);
> - atomic_set(&zone->refcount, 0);
> + refcount_set(&zone->refcount, 0);
> zone->chunk = DMZ_MAP_UNMAPPED;
>
> if (blkz->type == BLK_ZONE_TYPE_CONVENTIONAL) {
> @@ -1574,7 +1575,7 @@ struct dm_zone *dmz_get_zone_for_reclaim(struct dmz_metadata *zmd)
> void dmz_activate_zone(struct dm_zone *zone)
> {
> set_bit(DMZ_ACTIVE, &zone->flags);
> - atomic_inc(&zone->refcount);
> + refcount_inc(&zone->refcount);
> }
>
> /*
> @@ -1585,7 +1586,7 @@ void dmz_activate_zone(struct dm_zone *zone)
> */
> void dmz_deactivate_zone(struct dm_zone *zone)
> {
> - if (atomic_dec_and_test(&zone->refcount)) {
> + if (refcount_dec_and_test(&zone->refcount)) {
> WARN_ON(!test_bit(DMZ_ACTIVE, &zone->flags));
> clear_bit_unlock(DMZ_ACTIVE, &zone->flags);
> smp_mb__after_atomic();
> @@ -2308,7 +2309,7 @@ static void dmz_cleanup_metadata(struct dmz_metadata *zmd)
> mblk = list_first_entry(&zmd->mblk_dirty_list,
> struct dmz_mblock, link);
> dmz_dev_warn(zmd->dev, "mblock %llu still in dirty list (ref %u)",
> - (u64)mblk->no, atomic_read(&mblk->ref));
> + (u64)mblk->no, refcount_read(&mblk->ref));
> list_del_init(&mblk->link);
> rb_erase(&mblk->node, &zmd->mblk_rbtree);
> dmz_free_mblock(zmd, mblk);
> @@ -2326,8 +2327,8 @@ static void dmz_cleanup_metadata(struct dmz_metadata *zmd)
> root = &zmd->mblk_rbtree;
> rbtree_postorder_for_each_entry_safe(mblk, next, root, node) {
> dmz_dev_warn(zmd->dev, "mblock %llu ref %u still in rbtree",
> - (u64)mblk->no, atomic_read(&mblk->ref));
> - atomic_set(&mblk->ref, 0);
> + (u64)mblk->no, refcount_read(&mblk->ref));
> + refcount_set(&mblk->ref, 0);
> dmz_free_mblock(zmd, mblk);
> }
>
> diff --git a/drivers/md/dm-zoned.h b/drivers/md/dm-zoned.h
> index 12419f0bfe78..b7829a615d26 100644
> --- a/drivers/md/dm-zoned.h
> +++ b/drivers/md/dm-zoned.h
> @@ -78,7 +78,7 @@ struct dm_zone {
> unsigned long flags;
>
> /* Zone activation reference count */
> - atomic_t refcount;
> + refcount_t refcount;
>
> /* Zone write pointer block (relative to the zone start block) */
> unsigned int wp_block;
>
--
Damien Le Moal
Western Digital Research
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