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blk-mq: always free hctx after request queue is freed 

In normal queue cleanup path, hctx is released after request queue
is freed, see blk_mq_release().

However, in __blk_mq_update_nr_hw_queues(), hctx may be freed because
of hw queues shrinking. This way is easy to cause use-after-free,
because: one implicit rule is that it is safe to call almost all block
layer APIs if the request queue is alive; and one hctx may be retrieved
by one API, then the hctx can be freed by blk_mq_update_nr_hw_queues();
finally use-after-free is triggered.

Fixes this issue by always freeing hctx after releasing request queue.
If some hctxs are removed in blk_mq_update_nr_hw_queues(), introduce
a per-queue list to hold them, then try to resuse these hctxs if numa
node is matched.

Cc: Dongli Zhang <dongli.zhang@oracle.com>
Cc: James Smart <james.smart@broadcom.com>
Cc: Bart Van Assche <bart.vanassche@wdc.com>
Cc: linux-scsi@vger.kernel.org,
Cc: Martin K . Petersen <martin.petersen@oracle.com>,
Cc: Christoph Hellwig <hch@lst.de>,
Cc: James E . J . Bottomley <jejb@linux.vnet.ibm.com>,
Reviewed-by: Hannes Reinecke <hare@suse.com>
Tested-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2019-04-30 09:52:27 +08:00 committed by Jens Axboe
parent 7c6c5b7c91
commit 2f8f1336a4
3 changed files with 42 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

44
block/blk-mq.c
View File

@ -2269,6 +2269,10 @@ static void blk_mq_exit_hctx(struct request_queue *q,
set->ops->exit_hctx(hctx, hctx_idx);
blk_mq_remove_cpuhp(hctx);
spin_lock(&q->unused_hctx_lock);
list_add(&hctx->hctx_list, &q->unused_hctx_list);
spin_unlock(&q->unused_hctx_lock);
}
static void blk_mq_exit_hw_queues(struct request_queue *q,
@ -2351,6 +2355,8 @@ blk_mq_alloc_hctx(struct request_queue *q, struct blk_mq_tag_set *set,
hctx->queue = q;
hctx->flags = set->flags & ~BLK_MQ_F_TAG_SHARED;
INIT_LIST_HEAD(&hctx->hctx_list);
/*
* Allocate space for all possible cpus to avoid allocation at
* runtime
@ -2664,15 +2670,17 @@ static int blk_mq_alloc_ctxs(struct request_queue *q)
*/
void blk_mq_release(struct request_queue *q)
{
struct blk_mq_hw_ctx *hctx;
unsigned int i;
struct blk_mq_hw_ctx *hctx, *next;
int i;
cancel_delayed_work_sync(&q->requeue_work);
/* hctx kobj stays in hctx */
queue_for_each_hw_ctx(q, hctx, i) {
if (!hctx)
continue;
queue_for_each_hw_ctx(q, hctx, i)
WARN_ON_ONCE(hctx && list_empty(&hctx->hctx_list));
/* all hctx are in .unused_hctx_list now */
list_for_each_entry_safe(hctx, next, &q->unused_hctx_list, hctx_list) {
list_del_init(&hctx->hctx_list);
kobject_put(&hctx->kobj);
}
@ -2739,8 +2747,21 @@ static struct blk_mq_hw_ctx *blk_mq_alloc_and_init_hctx(
struct blk_mq_tag_set *set, struct request_queue *q,
int hctx_idx, int node)
{
struct blk_mq_hw_ctx *hctx;
struct blk_mq_hw_ctx *hctx = NULL, *tmp;
/* reuse dead hctx first */
spin_lock(&q->unused_hctx_lock);
list_for_each_entry(tmp, &q->unused_hctx_list, hctx_list) {
if (tmp->numa_node == node) {
hctx = tmp;
break;
}
}
if (hctx)
list_del_init(&hctx->hctx_list);
spin_unlock(&q->unused_hctx_lock);
if (!hctx)
hctx = blk_mq_alloc_hctx(q, set, node);
if (!hctx)
goto fail;
@ -2779,10 +2800,8 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
hctx = blk_mq_alloc_and_init_hctx(set, q, i, node);
if (hctx) {
if (hctxs[i]) {
if (hctxs[i])
blk_mq_exit_hctx(q, set, hctxs[i], i);
kobject_put(&hctxs[i]->kobj);
}
hctxs[i] = hctx;
} else {
if (hctxs[i])
@ -2813,9 +2832,7 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
if (hctx->tags)
blk_mq_free_map_and_requests(set, j);
blk_mq_exit_hctx(q, set, hctx, j);
kobject_put(&hctx->kobj);
hctxs[j] = NULL;
}
}
mutex_unlock(&q->sysfs_lock);
@ -2858,6 +2875,9 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
if (!q->queue_hw_ctx)
goto err_sys_init;
INIT_LIST_HEAD(&q->unused_hctx_list);
spin_lock_init(&q->unused_hctx_lock);
blk_mq_realloc_hw_ctxs(set, q);
if (!q->nr_hw_queues)
goto err_hctxs;

2
include/linux/blk-mq.h
View File

@ -70,6 +70,8 @@ struct blk_mq_hw_ctx {
struct dentry *sched_debugfs_dir;
#endif
struct list_head hctx_list;
/* Must be the last member - see also blk_mq_hw_ctx_size(). */
struct srcu_struct srcu[0];
};

7
include/linux/blkdev.h
View File

@ -535,6 +535,13 @@ struct request_queue {
struct mutex sysfs_lock;
/*
* for reusing dead hctx instance in case of updating
* nr_hw_queues
*/
struct list_head unused_hctx_list;
spinlock_t unused_hctx_lock;
atomic_t mq_freeze_depth;
#if defined(CONFIG_BLK_DEV_BSG)