From: Joe Thornber Fix a discard granularity calculation to work for non power of 2 block sizes. In order for thinp to passdown discard bios to the underlying data device, the data device must have a discard granularity that is a factor of the thinp block size. Originally this check was done by using bitops since the block_size was known to be a power of two. Introduced by commit f13945d75730081830b6f3360266950e2b7c9067 ("dm thin: support a non power of 2 discard_granularity"). Signed-off-by: Joe Thornber Signed-off-by: Alasdair G Kergon --- drivers/md/dm-thin.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) Index: linux/drivers/md/dm-thin.c =================================================================== --- linux.orig/drivers/md/dm-thin.c +++ linux/drivers/md/dm-thin.c @@ -1577,6 +1577,11 @@ static bool data_dev_supports_discard(st return q && blk_queue_discard(q); } +static bool is_factor(sector_t block_size, uint32_t n) +{ + return !sector_div(block_size, n); +} + /* * If discard_passdown was enabled verify that the data device * supports discards. Disable discard_passdown if not. @@ -1602,7 +1607,7 @@ static void disable_passdown_if_not_supp else if (data_limits->discard_granularity > block_size) reason = "discard granularity larger than a block"; - else if (block_size & (data_limits->discard_granularity - 1)) + else if (!is_factor(block_size, data_limits->discard_granularity)) reason = "discard granularity not a factor of block size"; if (reason) {