According to commit 4412efecf7fd ("Revert "blk-mq: remove code for
dealing with remapping queue""), for some devices queue hctx may not
being mapped, and tagset->tags[hctx_idx] will be released and be NULL.
If an IO scheduler is used on these devices, blk_mq_clear_rq_mapping()
will be called for all hctxs in blk_mq_sched_free_requests() during
scheduler switch, and these will be oops. So checking the existence of
tags[hctx_idx] before going on in blk_mq_clear_rq_mapping().
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
---
block/blk-mq.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 65d3a63aecc6..c3d701f44e49 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2297,6 +2297,10 @@ static void blk_mq_clear_rq_mapping(struct blk_mq_tag_set *set,
struct page *page;
unsigned long flags;
+ /* If the hctx is unmapped, drv_tags may be NULL */
+ if (!drv_tags)
+ return;
+
list_for_each_entry(page, &tags->page_list, lru) {
unsigned long start = (unsigned long)page_address(page);
unsigned long end = start + order_to_size(page->private);
--
2.29.2
