[PATCH] mm: thp: remove debug_cow switch

[PATCH] mm: thp: remove debug_cow switch

[Yang Shi]

Since commit 3917c80280c93a7123f1a3a6dcdb10a3ea19737d ("thp: change CoW
semantics for anon-THP"), the CoW page fault of THP has been rewritten,
debug_cow is not used anymore.  So, just remove it.

Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
---
 include/linux/huge_mm.h |  7 -------
 mm/huge_memory.c        | 21 ---------------------
 2 files changed, 28 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 71f2077..b8d7c36 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -181,13 +181,6 @@ static inline bool transhuge_vma_suitable(struct vm_area_struct *vma,
 #define transparent_hugepage_use_zero_page()				\
 	(transparent_hugepage_flags &					\
 	 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG))
-#ifdef CONFIG_DEBUG_VM
-#define transparent_hugepage_debug_cow()				\
-	(transparent_hugepage_flags &					\
-	 (1<<TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG))
-#else /* CONFIG_DEBUG_VM */
-#define transparent_hugepage_debug_cow() 0
-#endif /* CONFIG_DEBUG_VM */
 
 extern unsigned long thp_get_unmapped_area(struct file *filp,
 		unsigned long addr, unsigned long len, unsigned long pgoff,
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 78c84be..2f585d2 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -303,24 +303,6 @@ static ssize_t hpage_pmd_size_show(struct kobject *kobj,
 static struct kobj_attribute hpage_pmd_size_attr =
 	__ATTR_RO(hpage_pmd_size);
 
-#ifdef CONFIG_DEBUG_VM
-static ssize_t debug_cow_show(struct kobject *kobj,
-				struct kobj_attribute *attr, char *buf)
-{
-	return single_hugepage_flag_show(kobj, attr, buf,
-				TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
-}
-static ssize_t debug_cow_store(struct kobject *kobj,
-			       struct kobj_attribute *attr,
-			       const char *buf, size_t count)
-{
-	return single_hugepage_flag_store(kobj, attr, buf, count,
-				 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
-}
-static struct kobj_attribute debug_cow_attr =
-	__ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
-#endif /* CONFIG_DEBUG_VM */
-
 static struct attribute *hugepage_attr[] = {
 	&enabled_attr.attr,
 	&defrag_attr.attr,
@@ -329,9 +311,6 @@ static ssize_t debug_cow_store(struct kobject *kobj,
 #ifdef CONFIG_SHMEM
 	&shmem_enabled_attr.attr,
 #endif
-#ifdef CONFIG_DEBUG_VM
-	&debug_cow_attr.attr,
-#endif
 	NULL,
 };
 
-- 
1.8.3.1

Re: [PATCH] mm: thp: remove debug_cow switch

[Zi Yan]

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On 15 Jun 2020, at 21:29, Yang Shi wrote:

> Since commit 3917c80280c93a7123f1a3a6dcdb10a3ea19737d ("thp: change CoW
> semantics for anon-THP"), the CoW page fault of THP has been rewritten,
> debug_cow is not used anymore.  So, just remove it.
>
> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
> ---

Makes sense to me.

Reviewed-by: Zi Yan <ziy@nvidia.com>

—
Best Regards,
Yan Zi

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