[PATCH 4.2 110/258] dm thin: disable discard support for thin devices if pools is disabled

[Greg Kroah-Hartman]

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

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

From: Mike Snitzer <snitzer@xxxxxxxxxx>

commit 216076705d6ac291d42e0f8dd85e6a0da98c0fa3 upstream.

If the pool is configured with 'ignore_discard' its discard support is
disabled.  The pool's thin devices should also have queue_limits that
reflect discards are disabled.

Fixes: 34fbcf62 ("dm thin: range discard support")
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/md/dm-thin.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -4333,6 +4333,10 @@ static void thin_io_hints(struct dm_targ
 {
 	struct thin_c *tc = ti->private;
 	struct pool *pool = tc->pool;
+	struct queue_limits *pool_limits = dm_get_queue_limits(pool->pool_md);
+
+	if (!pool_limits->discard_granularity)
+		return; /* pool's discard support is disabled */
 
 	limits->discard_granularity = pool->sectors_per_block << SECTOR_SHIFT;
 	limits->max_discard_sectors = 2048 * 1024 * 16; /* 16G */


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