vma_migratable() is called to check if pages in vma can be migrated before go ahead to further actions. Currently it is used in below code path: - task_numa_work - mbind - move_pages For hugetlb mapping, whether vma is migratable or not is determined by: - CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION - arch_hugetlb_migration_supported Issue: current code only checks for CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION alone, and no code should use it directly. (note that current code in vma_migratable don't cause failure or bug because unmap_and_move_huge_page() will catch unsupported hugepage and handle it properly) This patch checks the two factors by hugepage_migration_supported for impoving code logic and robustness. It will enable early bail out of hugepage migration procedure, but because currently all architecture supporting hugepage migration is able to support all page size, we would not see performance gain with this patch applied. vma_migratable() is moved to mm/mempolicy.c, because of the circular reference of mempolicy.h and hugetlb.h cause defining it as inline not feasible.
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| @@ -173,34 +173,7 @@ extern int mpol_parse_str(char *str, struct mempolicy **mpol); · 172 unmodified lines | |||
| 173 | extern void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol); | 173 | extern void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol); |
| 174 | 174 | ||
| 175 | /* Check if a vma is migratable */ | 175 | /* Check if a vma is migratable */ |
| 176 | static inline bool vma_migratable(struct vm_area_struct *vma) | 176 | extern bool vma_migratable(struct vm_area_struct *vma); |
| 177 | { | ||
| 178 | if (vma->vm_flags & (VM_IO | VM_PFNMAP)) | ||
| 179 | return false; | ||
| 180 | |||
| 181 | /* | ||
| 182 | * DAX device mappings require predictable access latency, so avoid | ||
| 183 | * incurring periodic faults. | ||
| 184 | */ | ||
| 185 | if (vma_is_dax(vma)) | ||
| 186 | return false; | ||
| 187 | |||
| 188 | #ifndef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION | ||
| 189 | if (vma->vm_flags & VM_HUGETLB) | ||
| 190 | return false; | ||
| 191 | #endif | ||
| 192 | |||
| 193 | /* | ||
| 194 | * Migration allocates pages in the highest zone. If we cannot | ||
| 195 | * do so then migration (at least from node to node) is not | ||
| 196 | * possible. | ||
| 197 | */ | ||
| 198 | if (vma->vm_file && | ||
| 199 | gfp_zone(mapping_gfp_mask(vma->vm_file->f_mapping)) | ||
| 200 | < policy_zone) | ||
| 201 | return false; | ||
| 202 | return true; | ||
| 203 | } | ||
| 204 | 177 | ||
| 205 | extern int mpol_misplaced(struct page *, struct vm_area_struct *, unsigned long); | 178 | extern int mpol_misplaced(struct page *, struct vm_area_struct *, unsigned long); |
| 206 | extern void mpol_put_task_policy(struct task_struct *); | 179 | extern void mpol_put_task_policy(struct task_struct *); |