From 0fcb04d59351f790efb8da18edefd6ab4d9bbf3b Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Mon, 23 Nov 2015 13:44:38 -0500 Subject: [PATCH] dm thin: fix regression in advertised discard limits When establishing a thin device's discard limits we cannot rely on the underlying thin-pool device's discard capabilities (which are inherited from the thin-pool's underlying data device) given that DM thin devices must provide discard support even when the thin-pool's underlying data device doesn't support discards. Users were exposed to this thin device discard limits regression if their thin-pool's underlying data device does _not_ support discards. This regression caused all upper-layers that called the blkdev_issue_discard() interface to not be able to issue discards to thin devices (because discard_granularity was 0). This regression wasn't caught earlier because the device-mapper-test-suite's extensive 'thin-provisioning' discard tests are only ever performed against thin-pool's with data devices that support discards. Fix is to have thin_io_hints() test the pool's 'discard_enabled' feature rather than inferring whether or not a thin device's discard support should be enabled by looking at the thin-pool's discard_granularity. Fixes: 216076705 ("dm thin: disable discard support for thin devices if pool's is disabled") Reported-by: Mike Gerber Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org # 4.1+ --- drivers/md/dm-thin.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index 9f0b94fad361..63903a5a5d9e 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -4250,10 +4250,9 @@ static void thin_io_hints(struct dm_target *ti, struct queue_limits *limits) { 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 */ + if (!pool->pf.discard_enabled) + return; limits->discard_granularity = pool->sectors_per_block << SECTOR_SHIFT; limits->max_discard_sectors = 2048 * 1024 * 16; /* 16G */