Commit 9685e6e3 authored by Gregory Price's avatar Gregory Price Committed by Andrew Morton
Browse files

mm/mempolicy: refactor a read-once mechanism into a function for re-use 

Move the use of barrier() to force policy->nodemask onto the stack into a
function `read_once_policy_nodemask` so that it may be re-used.

Link: https://lkml.kernel.org/r/20240202170238.90004-3-gregory.price@memverge.com


Signed-off-by: default avatarGregory Price <gregory.price@memverge.com>
Suggested-by: default avatar"Huang, Ying" <ying.huang@intel.com>
Reviewed-by: default avatar"Huang, Ying" <ying.huang@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Hasan Al Maruf <Hasan.Maruf@amd.com>
Cc: Honggyu Kim <honggyu.kim@sk.com>
Cc: Hyeongtak Ji <hyeongtak.ji@sk.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Ravi Jonnalagadda <ravis.opensrc@micron.com>
Cc: Srinivasulu Thanneeru <sthanneeru.opensrc@micron.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent dce41f5a

mm/mempolicy.c

+16 −10
Original line number Diff line number Diff line
@@ -1905,6 +1905,20 @@ unsigned int mempolicy_slab_node(void) 
	}

}



static unsigned int read_once_policy_nodemask(struct mempolicy *pol,

					      nodemask_t *mask)

{

	/*

	 * barrier stabilizes the nodemask locally so that it can be iterated

	 * over safely without concern for changes. Allocators validate node

	 * selection does not violate mems_allowed, so this is safe.

	 */

	barrier();

	memcpy(mask, &pol->nodes, sizeof(nodemask_t));

	barrier();

	return nodes_weight(*mask);

}



/*

 * Do static interleaving for interleave index @ilx.  Returns the ilx'th

 * node in pol->nodes (starting from ilx=0), wrapping around if ilx
@@ -1912,20 +1926,12 @@ unsigned int mempolicy_slab_node(void) 
 */

static unsigned int interleave_nid(struct mempolicy *pol, pgoff_t ilx)

{

	nodemask_t nodemask = pol->nodes;

	nodemask_t nodemask;

	unsigned int target, nnodes;

	int i;

	int nid;

	/*

	 * The barrier will stabilize the nodemask in a register or on

	 * the stack so that it will stop changing under the code.

	 *

	 * Between first_node() and next_node(), pol->nodes could be changed

	 * by other threads. So we put pol->nodes in a local stack.

	 */

	barrier();



	nnodes = nodes_weight(nodemask);

	nnodes = read_once_policy_nodemask(pol, &nodemask);

	if (!nnodes)

		return numa_node_id();

	target = ilx % nnodes;