The basic idea is the same as with PTE level: the lock is embedded into struct page of table's page. We can't use mm->pmd_huge_pte to store pgtables for THP, since we don't take mm->page_table_lock anymore. Let's reuse page->lru of table's page for that. pgtable_pmd_page_ctor() returns true, if initialization is successful and false otherwise. Current implementation never fails, but assumption that constructor can fail will help to port it to -rt where spinlock_t is rather huge and cannot be embedded into struct page -- dynamic allocation is required.
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| @@ -560,7 +560,7 @@ static void check_mm(struct mm_struct *mm) · 559 unmodified lines | |||
| 560 | "mm:%p idx:%d val:%ld\n", mm, i, x); | 560 | "mm:%p idx:%d val:%ld\n", mm, i, x); |
| 561 | } | 561 | } |
| 562 | 562 | ||
| 563 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE | 563 | #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS |
| 564 | VM_BUG_ON(mm->pmd_huge_pte); | 564 | VM_BUG_ON(mm->pmd_huge_pte); |
| 565 | #endif | 565 | #endif |
| 566 | } | 566 | } |
| @@ -814,7 +814,7 @@ struct mm_struct *dup_mm(struct task_struct *tsk) · 247 unmodified lines | |||
| 814 | memcpy(mm, oldmm, sizeof(*mm)); | 814 | memcpy(mm, oldmm, sizeof(*mm)); |
| 815 | mm_init_cpumask(mm); | 815 | mm_init_cpumask(mm); |
| 816 | 816 | ||
| 817 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE | 817 | #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS |
| 818 | mm->pmd_huge_pte = NULL; | 818 | mm->pmd_huge_pte = NULL; |
| 819 | #endif | 819 | #endif |
| 820 | if (!mm_init(mm, tsk)) | 820 | if (!mm_init(mm, tsk)) |