linux-kernel - [PATCH -next v2 0/2] md/raid5-cache: fix a deadlock in r5l_exit

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Message-Id: <20230628010756.70649-1-yukuai1@huaweicloud.com>
Date:   Wed, 28 Jun 2023 09:07:54 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     xni@...hat.com, logang@...tatee.com, hch@....de, song@...nel.org,
        shli@...com
Cc:     linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
        yukuai3@...wei.com, yukuai1@...weicloud.com, yi.zhang@...wei.com,
        yangerkun@...wwe.com
Subject: [PATCH -next v2 0/2] md/raid5-cache: fix a deadlock in r5l_exit_log()

From: Yu Kuai <yukuai3@...wei.com>

Changes in v2:
 - remove a now unused local variable in patch 2;

Commit b13015af94cf ("md/raid5-cache: Clear conf->log after finishing
work") introduce a new problem:

// caller hold reconfig_mutex
r5l_exit_log
 flush_work(&log->disable_writeback_work)
			r5c_disable_writeback_async
			 wait_event
			  /*
			   * conf->log is not NULL, and mddev_trylock()
			   * will fail, wait_event() can never pass.
			   */
 conf->log = NULL

patch 1 revert this patch, an patch 2 fix the original problem in a
different way.

Noted this problem is just found by code review, and I think this is
probably the reason that some mdadm tests is broken.

Yu Kuai (2):
  md/raid5-cache: Revert "md/raid5-cache: Clear conf->log after
    finishing work"
  md/raid5-cache: fix null-ptr-deref in r5l_reclaim_thread()

 drivers/md/raid5-cache.c | 25 ++++++++++---------------
 1 file changed, 10 insertions(+), 15 deletions(-)

-- 
2.39.2