From: Gregory Price <gourry.memverge@gmail.com> mainline inclusion from mainline-v6.9-rc1 commit 9685e6e30d116d72fb013b0bce261a676b7575c1 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I9OHHN Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- 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> Signed-off-by: Ze Zuo <zuoze1@huawei.com> --- mm/mempolicy.c | 26 ++++++++++++++++---------- 1 file changed, 16 insertions(+), 10 deletions(-) diff --git a/mm/mempolicy.c b/mm/mempolicy.c index bdf22ee37c72..7983a65664d9 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -2095,6 +2095,20 @@ 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 @@ -2102,20 +2116,12 @@ 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; -- 2.25.1