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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: Gregory Price <gregory.price@memverge.com>
Suggested-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: "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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Gregory Price 2024-02-02 12:02:36 -05:00 committed by Andrew Morton
parent dce41f5ae2
commit 9685e6e30d
1 changed files with 16 additions and 10 deletions
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26
mm/mempolicy.c
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@ -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;