Commit 58051b94 authored by Joe Thornber's avatar Joe Thornber Committed by Alasdair G Kergon
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dm thin: fix non power of two discard granularity calc 



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 f13945d7
("dm thin: support a non power of 2 discard_granularity").

Signed-off-by: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent f046f89a

drivers/md/dm-thin.c

+6 −1
Original line number Diff line number Diff line
@@ -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) {

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