@@ -2503,10 +2503,10 @@ static int blk_mq_hw_ctx_size(struct blk_mq_tag_set *tag_set)
return hw_ctx_size;
}
-static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
+static bool blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
struct request_queue *q)
{
- int i, j;
+ int i, j, end;
struct blk_mq_hw_ctx **hctxs = q->queue_hw_ctx;
/* protect against switching io scheduler */
@@ -2542,7 +2542,24 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
}
blk_mq_hctx_kobj_init(hctxs[i]);
}
- for (j = i; j < q->nr_hw_queues; j++) {
+
+ if (i != set->nr_hw_queues) {
+ /*
+ * Increasing nr_hw_queues fails. Free the newly allocated
+ * hctxs and keep the previous q->nr_hw_queues.
+ */
+ j = q->nr_hw_queues;
+ end = i;
+ } else {
+ /*
+ * If nr_hw_queues is decreased, free the redundant hctxs.
+ */
+ j = i;
+ end = q->nr_hw_queues;
+ q->nr_hw_queues = set->nr_hw_queues;
+ }
+
+ for (; j < end; j++) {
struct blk_mq_hw_ctx *hctx = hctxs[j];
if (hctx) {
@@ -2554,8 +2571,9 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
}
}
- q->nr_hw_queues = i;
mutex_unlock(&q->sysfs_lock);
+
+ return (q->nr_hw_queues == set->nr_hw_queues);
}
struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
@@ -2939,6 +2957,7 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
{
struct request_queue *q;
LIST_HEAD(head);
+ int prev_nr_hw_queues;
lockdep_assert_held(&set->tag_list_lock);
@@ -2967,10 +2986,21 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
blk_mq_sysfs_unregister(q);
}
+ prev_nr_hw_queues = set->nr_hw_queues;
set->nr_hw_queues = nr_hw_queues;
+again:
blk_mq_update_queue_map(set);
list_for_each_entry(q, &set->tag_list, tag_set_list) {
- blk_mq_realloc_hw_ctxs(set, q);
+ /*
+ * If increasing nr_hw_queues fail, fallback to previous
+ * nr_hw_queues.
+ */
+ if (!blk_mq_realloc_hw_ctxs(set, q)) {
+ pr_warn("updating nr_hw_queues to %d fails, fallback to %d.\n",
+ nr_hw_queues, prev_nr_hw_queues);
+ set->nr_hw_queues = prev_nr_hw_queues;
+ goto again;
+ }
blk_mq_map_swqueue(q);
}
When we try to increate the nr_hw_queues, we may fail due to shortage of memory or other reason, then blk_mq_realloc_hw_ctxs stops and some entries in q->queue_hw_ctx are left with NULL. However, because queue map has been updated with new nr_hw_queues, some cpus have been mapped to hw queue which just encounters allocation failure, thus blk_mq_map_queue could return NULL. This will cause panic in following blk_mq_map_swqueue. To fix it, let blk_mq_realloc_hw_ctxs return false to skip blk_mq_map_swqueue and fallback to previous nr_hw_queues in case of increasing nr_hw_queues failure. Reported-by: syzbot+83e8cbe702263932d9d4@syzkaller.appspotmail.com Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com> --- block/blk-mq.c | 40 +++++++++++++++++++++++++++++++++++----- 1 file changed, 35 insertions(+), 5 deletions(-)