commit bda420b98505 ("numa balancing: migrate on fault among multiple bound nodes") adds new flag MPOL_F_NUMA_BALANCING to enable NUMA balancing for MPOL_BIND memory policy. When the cpuset of tasks changes, the mempolicy of the task is rebound by mpol_rebind_nodemask(). When MPOL_F_STATIC_NODES and MPOL_F_RELATIVE_NODES are both not set, the behaviour of rebinding should be same whenever MPOL_F_NUMA_BALANCING is set or not. So, when an application calls set_mempolicy() with MPOL_F_NUMA_BALANCING set but both MPOL_F_STATIC_NODES and MPOL_F_RELATIVE_NODES cleared, mempolicy.w.cpuset_mems_allowed should be set to cpuset_current_mems_allowed nodemask. However, in current implementation, mpol_store_user_nodemask() wrongly returns true, causing mempolicy->w.user_nodemask to be incorrectly set to the user-specified nodemask. Later, when the cpuset of the application changes, mpol_rebind_nodemask() ends up rebinding based on the user-specified nodemask rather than the cpuset_mems_allowed nodemask as intended. To fix this, only set mempolicy->w.user_nodemask to the user-specified nodemask if MPOL_F_STATIC_NODES or MPOL_F_RELATIVE_NODES is present. Fixes: bda420b98505 ("numa balancing: migrate on fault among multiple bound nodes") Reviewed-by: Gregory Price Reviewed-by: Huang Ying Signed-off-by: Jinjiang Tu --- Change in v3: * update changelog * collect RB from Huang Ying include/uapi/linux/mempolicy.h | 3 +++ mm/mempolicy.c | 2 +- 2 files changed, 4 insertions(+), 1 deletion(-) diff --git a/include/uapi/linux/mempolicy.h b/include/uapi/linux/mempolicy.h index 8fbbe613611a..6c962d866e86 100644 --- a/include/uapi/linux/mempolicy.h +++ b/include/uapi/linux/mempolicy.h @@ -39,6 +39,9 @@ enum { #define MPOL_MODE_FLAGS \ (MPOL_F_STATIC_NODES | MPOL_F_RELATIVE_NODES | MPOL_F_NUMA_BALANCING) +/* Whether the nodemask is specified by users */ +#define MPOL_USER_NODEMASK_FLAGS (MPOL_F_STATIC_NODES | MPOL_F_RELATIVE_NODES) + /* Flags for get_mempolicy */ #define MPOL_F_NODE (1<<0) /* return next IL mode instead of node mask */ #define MPOL_F_ADDR (1<<1) /* look up vma using address */ diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 68a98ba57882..76da50425712 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -365,7 +365,7 @@ static const struct mempolicy_operations { static inline int mpol_store_user_nodemask(const struct mempolicy *pol) { - return pol->flags & MPOL_MODE_FLAGS; + return pol->flags & MPOL_USER_NODEMASK_FLAGS; } static void mpol_relative_nodemask(nodemask_t *ret, const nodemask_t *orig, -- 2.43.0