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Message-Id: <20250926093343.1000-3-laoar.shao@gmail.com>
Date: Fri, 26 Sep 2025 17:33:33 +0800
From: Yafang Shao <laoar.shao@...il.com>
To: akpm@...ux-foundation.org,
david@...hat.com,
ziy@...dia.com,
baolin.wang@...ux.alibaba.com,
lorenzo.stoakes@...cle.com,
Liam.Howlett@...cle.com,
npache@...hat.com,
ryan.roberts@....com,
dev.jain@....com,
hannes@...xchg.org,
usamaarif642@...il.com,
gutierrez.asier@...wei-partners.com,
willy@...radead.org,
ast@...nel.org,
daniel@...earbox.net,
andrii@...nel.org,
ameryhung@...il.com,
rientjes@...gle.com,
corbet@....net,
21cnbao@...il.com,
shakeel.butt@...ux.dev,
tj@...nel.org,
lance.yang@...ux.dev
Cc: bpf@...r.kernel.org,
linux-mm@...ck.org,
linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org,
Yafang Shao <laoar.shao@...il.com>,
Yang Shi <shy828301@...il.com>
Subject: [PATCH v8 mm-new 02/12] mm: thp: remove vm_flags parameter from khugepaged_enter_vma()
The khugepaged_enter_vma() function requires handling in two specific
scenarios:
1. New VMA creation
When a new VMA is created, if vma->vm_mm is not present in
khugepaged_mm_slot, it must be added. In this case,
khugepaged_enter_vma() is called after vma->vm_flags have been set,
allowing direct use of the VMA's flags.
2. VMA flag modification
When vma->vm_flags are modified (particularly when VM_HUGEPAGE is set),
the system must recheck whether to add vma->vm_mm to khugepaged_mm_slot.
Currently, khugepaged_enter_vma() is called before the flag update, so
the call must be relocated to occur after vma->vm_flags have been set.
Additionally, khugepaged_enter_vma() is invoked in other contexts, such as
during VMA merging. However, these calls are unnecessary because the
existing VMA already ensures that vma->vm_mm is registered in
khugepaged_mm_slot. While removing these redundant calls represents a
potential optimization, that change should be addressed separately.
Because VMA merging only occurs when the vm_flags of both VMAs are
identical (excluding special flags like VM_SOFTDIRTY), we can safely use
target->vm_flags instead.
After this change, we can further remove vm_flags parameter from
thp_vma_allowable_order(). That will be handled in a followup patch.
Signed-off-by: Yafang Shao <laoar.shao@...il.com>
Cc: Yang Shi <shy828301@...il.com>
---
include/linux/khugepaged.h | 6 ++----
mm/huge_memory.c | 2 +-
mm/khugepaged.c | 11 ++---------
mm/madvise.c | 7 +++++++
mm/vma.c | 6 +++---
5 files changed, 15 insertions(+), 17 deletions(-)
diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h
index f14680cd9854..b30814d3d665 100644
--- a/include/linux/khugepaged.h
+++ b/include/linux/khugepaged.h
@@ -13,8 +13,7 @@ extern void khugepaged_destroy(void);
extern int start_stop_khugepaged(void);
extern void __khugepaged_enter(struct mm_struct *mm);
extern void __khugepaged_exit(struct mm_struct *mm);
-extern void khugepaged_enter_vma(struct vm_area_struct *vma,
- vm_flags_t vm_flags);
+extern void khugepaged_enter_vma(struct vm_area_struct *vma);
extern void khugepaged_enter_mm(struct mm_struct *mm);
extern void khugepaged_min_free_kbytes_update(void);
extern bool current_is_khugepaged(void);
@@ -39,8 +38,7 @@ static inline void khugepaged_fork(struct mm_struct *mm, struct mm_struct *oldmm
static inline void khugepaged_exit(struct mm_struct *mm)
{
}
-static inline void khugepaged_enter_vma(struct vm_area_struct *vma,
- vm_flags_t vm_flags)
+static inline void khugepaged_enter_vma(struct vm_area_struct *vma)
{
}
static inline void khugepaged_enter_mm(struct mm_struct *mm)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 1b81680b4225..ac6601f30e65 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1346,7 +1346,7 @@ vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
ret = vmf_anon_prepare(vmf);
if (ret)
return ret;
- khugepaged_enter_vma(vma, vma->vm_flags);
+ khugepaged_enter_vma(vma);
if (!(vmf->flags & FAULT_FLAG_WRITE) &&
!mm_forbids_zeropage(vma->vm_mm) &&
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index f47ac8c19447..04121ae7d18d 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -353,12 +353,6 @@ int hugepage_madvise(struct vm_area_struct *vma,
#endif
*vm_flags &= ~VM_NOHUGEPAGE;
*vm_flags |= VM_HUGEPAGE;
- /*
- * If the vma become good for khugepaged to scan,
- * register it here without waiting a page fault that
- * may not happen any time soon.
- */
- khugepaged_enter_vma(vma, *vm_flags);
break;
case MADV_NOHUGEPAGE:
*vm_flags &= ~VM_HUGEPAGE;
@@ -467,10 +461,9 @@ void khugepaged_enter_mm(struct mm_struct *mm)
__khugepaged_enter(mm);
}
-void khugepaged_enter_vma(struct vm_area_struct *vma,
- vm_flags_t vm_flags)
+void khugepaged_enter_vma(struct vm_area_struct *vma)
{
- if (!thp_vma_allowable_order(vma, vm_flags, TVA_KHUGEPAGED, PMD_ORDER))
+ if (!thp_vma_allowable_order(vma, vma->vm_flags, TVA_KHUGEPAGED, PMD_ORDER))
return;
khugepaged_enter_mm(vma->vm_mm);
diff --git a/mm/madvise.c b/mm/madvise.c
index 35ed4ab0d7c5..ab8b5d47badb 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1425,6 +1425,13 @@ static int madvise_vma_behavior(struct madvise_behavior *madv_behavior)
VM_WARN_ON_ONCE(madv_behavior->lock_mode != MADVISE_MMAP_WRITE_LOCK);
error = madvise_update_vma(new_flags, madv_behavior);
+ /*
+ * If the vma become good for khugepaged to scan,
+ * register it here without waiting a page fault that
+ * may not happen any time soon.
+ */
+ if (!error && new_flags & VM_HUGEPAGE)
+ khugepaged_enter_mm(vma->vm_mm);
out:
/*
* madvise() returns EAGAIN if kernel resources, such as
diff --git a/mm/vma.c b/mm/vma.c
index a1ec405bda25..6a548b0d64cd 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -973,7 +973,7 @@ static __must_check struct vm_area_struct *vma_merge_existing_range(
if (err || commit_merge(vmg))
goto abort;
- khugepaged_enter_vma(vmg->target, vmg->vm_flags);
+ khugepaged_enter_vma(vmg->target);
vmg->state = VMA_MERGE_SUCCESS;
return vmg->target;
@@ -1093,7 +1093,7 @@ struct vm_area_struct *vma_merge_new_range(struct vma_merge_struct *vmg)
* following VMA if we have VMAs on both sides.
*/
if (vmg->target && !vma_expand(vmg)) {
- khugepaged_enter_vma(vmg->target, vmg->vm_flags);
+ khugepaged_enter_vma(vmg->target);
vmg->state = VMA_MERGE_SUCCESS;
return vmg->target;
}
@@ -2520,7 +2520,7 @@ static int __mmap_new_vma(struct mmap_state *map, struct vm_area_struct **vmap)
* call covers the non-merge case.
*/
if (!vma_is_anonymous(vma))
- khugepaged_enter_vma(vma, map->vm_flags);
+ khugepaged_enter_vma(vma);
*vmap = vma;
return 0;
--
2.47.3
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