From: Joe Thornber Date: Mon, 18 Mar 2013 22:57:27 +0000 (+1100) Subject: Fix a discard granularity calculation to work for non power of 2 block sizes. X-Git-Tag: next-20130320~49^2~9 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=a66c52b50ee88c48e1bdc93803eaaf2f77d99321;p=karo-tx-linux.git 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 --- diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index ab95e5ff3758..004ad1652b73 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -1577,6 +1577,11 @@ static bool data_dev_supports_discard(struct pool_c *pt) 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_supported(struct pool_c *pt) 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) {