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From: Hou Tao <>
To: Jens Axboe <>, Ming Lei <>
Cc: <>
Subject: [PATCH] block: check the existence of tags[hctx_idx] in blk_mq_clear_rq_mapping()
Date: Thu, 9 Sep 2021 17:00:54 +0800	[thread overview]
Message-ID: <> (raw)

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 <>
 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);

             reply	other threads:[~2021-09-09  8:46 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-09  9:00 Hou Tao [this message]
2021-09-09  9:19 ` [PATCH] block: check the existence of tags[hctx_idx] in blk_mq_clear_rq_mapping() Ming Lei
2021-09-09 11:14   ` Hou Tao
2021-09-13  1:43     ` Ming Lei

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