linux-kernel - [PATCH 4.18 056/145] dm thin: stop no_space_timeout worker when switching to write-mode

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Date:   Fri,  7 Sep 2018 23:08:42 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hou Tao <houtao1@...wei.com>,
        Mike Snitzer <snitzer@...hat.com>
Subject: [PATCH 4.18 056/145] dm thin: stop no_space_timeout worker when switching to write-mode

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hou Tao <houtao1@...wei.com>

commit 75294442d896f2767be34f75aca7cc2b0d01301f upstream.

Now both check_for_space() and do_no_space_timeout() will read & write
pool->pf.error_if_no_space.  If these functions run concurrently, as
shown in the following case, the default setting of "queue_if_no_space"
can get lost.

precondition:
    * error_if_no_space = false (aka "queue_if_no_space")
    * pool is in Out-of-Data-Space (OODS) mode
    * no_space_timeout worker has been queued

CPU 0:                          CPU 1:
// delete a thin device
process_delete_mesg()
// check_for_space() invoked by commit()
set_pool_mode(pool, PM_WRITE)
    pool->pf.error_if_no_space = \
     pt->requested_pf.error_if_no_space

				// timeout, pool is still in OODS mode
				do_no_space_timeout
				    // "queue_if_no_space" config is lost
				    pool->pf.error_if_no_space = true
    pool->pf.mode = new_mode

Fix it by stopping no_space_timeout worker when switching to write mode.

Fixes: bcc696fac11f ("dm thin: stay in out-of-data-space mode once no_space_timeout expires")
Cc: stable@...r.kernel.org
Signed-off-by: Hou Tao <houtao1@...wei.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/md/dm-thin.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -2520,6 +2520,8 @@ static void set_pool_mode(struct pool *p
 	case PM_WRITE:
 		if (old_mode != new_mode)
 			notify_of_pool_mode_change(pool, "write");
+		if (old_mode == PM_OUT_OF_DATA_SPACE)
+			cancel_delayed_work_sync(&pool->no_space_timeout);
 		pool->out_of_data_space = false;
 		pool->pf.error_if_no_space = pt->requested_pf.error_if_no_space;
 		dm_pool_metadata_read_write(pool->pmd);