FAILED: patch "[PATCH] dm thin: stop no_space_timeout worker when switching to" failed to apply to 4.4-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From 75294442d896f2767be34f75aca7cc2b0d01301f Mon Sep 17 00:00:00 2001
From: Hou Tao <houtao1@xxxxxxxxxx>
Date: Thu, 2 Aug 2018 16:18:24 +0800
Subject: [PATCH] dm thin: stop no_space_timeout worker when switching to
 write-mode

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@xxxxxxxxxxxxxxx
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 5997d6808b57..7bd60a150f8f 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -2503,6 +2503,8 @@ static void set_pool_mode(struct pool *pool, enum pool_mode new_mode)
 	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);