Re: [PATCH 2/3] mm: huge_memory: add thp_vma_disabled()

[David Hildenbrand <david@redhat.com>]

On 10.10.24 16:41, David Hildenbrand wrote:
> On 10.10.24 08:10, Kefeng Wang wrote:
>> Add thp_vma_disabled() helper to shared by shmem_allowable_huge_orders()
>> and __thp_vma_allowable_orders().
>>
>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>> ---
>>    include/linux/huge_mm.h | 19 +++++++++++++++++++
>>    mm/huge_memory.c        | 13 +------------
>>    mm/shmem.c              |  7 +------
>>    3 files changed, 21 insertions(+), 18 deletions(-)
>>
>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
>> index 795df660efa5..d77891332b35 100644
>> --- a/include/linux/huge_mm.h
>> +++ b/include/linux/huge_mm.h
>> @@ -309,6 +309,25 @@ struct thpsize {
>>    	(transparent_hugepage_flags &					\
>>    	 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG))
>>    
>> +static inline bool thp_vma_disabled(struct vm_area_struct *vma,
>> +				    unsigned long vm_flags)
>> +{
>>
> 
> I might need a patch like this for an independent fix, and the more I
> look at this the more I hate the separate vm_flags and the optional vma
> argument.
> 
> Let me try to improve things.
> 
> Long term we can get rid of the vm_flags, it just needs some madvise()
> massaging.

For the time being I suggest this:

 From 318c25742380cdf15c8c807e5e8a52cabc217ef4 Mon Sep 17 00:00:00 2001
From: Kefeng Wang <wangkefeng.wang@huawei.com>
Date: Thu, 10 Oct 2024 14:10:23 +0800
Subject: [PATCH] mm: huge_memory: add vma_thp_disabled() and
  thp_disabled_by_hw()

Add vma_thp_disabled() and thp_disabled_by_hw() helpers to be shared by
shmem_allowable_huge_orders() and __thp_vma_allowable_orders().

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
[ rename to vma_thp_disabled(), split out thp_disabled_by_hw() ]
Signed-off-by: David Hildenbrand <david@redhat.com>
---
  include/linux/huge_mm.h | 18 ++++++++++++++++++
  mm/huge_memory.c        | 13 +------------
  mm/shmem.c              |  7 +------
  3 files changed, 20 insertions(+), 18 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 67d0ab3c3bba..57b62fd1ccb4 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -322,6 +322,24 @@ struct thpsize {
  	(transparent_hugepage_flags &					\
  	 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG))
  
+static inline bool vma_thp_disabled(struct vm_area_struct *vma,
+		unsigned long vm_flags)
+{
+	/*
+	 * Explicitly disabled through madvise or prctl, or some
+	 * architectures may disable THP for some mappings, for
+	 * example, s390x kvm.
+	 */
+	return (vm_flags & VM_NOHUGEPAGE) ||
+	       test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags);
+}
+
+static inline bool thp_disabled_by_hw(void)
+{
+	/* If the hardware/firmware marked hugepage support disabled. */
+	return transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED);
+}
+
  unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
  		unsigned long len, unsigned long pgoff, unsigned long flags);
  unsigned long thp_get_unmapped_area_vmflags(struct file *filp, unsigned long addr,
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 3ca89e0279a7..ffbf0add2a82 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -109,18 +109,7 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
  	if (!vma->vm_mm)		/* vdso */
  		return 0;
  
-	/*
-	 * Explicitly disabled through madvise or prctl, or some
-	 * architectures may disable THP for some mappings, for
-	 * example, s390 kvm.
-	 * */
-	if ((vm_flags & VM_NOHUGEPAGE) ||
-	    test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
-		return 0;
-	/*
-	 * If the hardware/firmware marked hugepage support disabled.
-	 */
-	if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED))
+	if (thp_disabled_by_hw() || vma_thp_disabled(vma, vm_flags))
  		return 0;
  
  	/* khugepaged doesn't collapse DAX vma, but page fault is fine. */
diff --git a/mm/shmem.c b/mm/shmem.c
index 4f11b5506363..c5adb987b23c 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1664,12 +1664,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode,
  	loff_t i_size;
  	int order;
  
-	if (vma && ((vm_flags & VM_NOHUGEPAGE) ||
-	    test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)))
-		return 0;
-
-	/* If the hardware/firmware marked hugepage support disabled. */
-	if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED))
+	if (thp_disabled_by_hw() || (vma && vma_thp_disabled(vma, vm_flags)))
  		return 0;
  
  	global_huge = shmem_huge_global_enabled(inode, index, write_end,
-- 
2.46.1


-- 
Cheers,

David / dhildenb