The patch titled
Subject: mm/mempolicy: refactor a read-once mechanism into a function for re-use
has been added to the -mm mm-unstable branch. Its filename is
mm-mempolicy-refactor-a-read-once-mechanism-into-a-function-for-re-use.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mempolicy-refactor-a-read-once-mechanism-into-a-function-for-re-use.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Gregory Price <gourry.memverge@xxxxxxxxx>
Subject: mm/mempolicy: refactor a read-once mechanism into a function for re-use
Date: Tue, 30 Jan 2024 13:20:45 -0500
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/20240130182046.74278-3-gregory.price@xxxxxxxxxxxx
Signed-off-by: Gregory Price <gregory.price@xxxxxxxxxxxx>
Suggested-by: Huang Ying <ying.huang@xxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Frank van der Linden <fvdl@xxxxxxxxxx>
Cc: Hasan Al Maruf <Hasan.Maruf@xxxxxxx>
Cc: Honggyu Kim <honggyu.kim@xxxxxx>
Cc: Hyeongtak Ji <hyeongtak.ji@xxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Rakie Kim <rakie.kim@xxxxxx>
Cc: Ravi Jonnalagadda <ravis.opensrc@xxxxxxxxxx>
Cc: Srinivasulu Thanneeru <sthanneeru.opensrc@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mempolicy.c | 26 ++++++++++++++++----------
1 file changed, 16 insertions(+), 10 deletions(-)
--- a/mm/mempolicy.c~mm-mempolicy-refactor-a-read-once-mechanism-into-a-function-for-re-use
+++ a/mm/mempolicy.c
@@ -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;
_
Patches currently in -mm which might be from gourry.memverge@xxxxxxxxx are
mm-mempolicy-refactor-a-read-once-mechanism-into-a-function-for-re-use.patch
mm-mempolicy-introduce-mpol_weighted_interleave-for-weighted-interleaving.patch
