mm/page_vma_mapped.c: check possible huge PMD map with transhuge_vma_suitable()

IIUC page_vma_mapped_walk() checks if the vma is possibly huge PMD mapped
with transparent_hugepage_active() and "pvmw->nr_pages >= HPAGE_PMD_NR".

Actually pvmw->nr_pages is returned by compound_nr() or folio_nr_pages(),
so the page should be THP as long as "pvmw->nr_pages >= HPAGE_PMD_NR".
And it is guaranteed THP is allocated for valid VMA in the first place.
But it may be not PMD mapped if the VMA is file VMA and it is not properly
aligned.  The transhuge_vma_suitable() is used to do such check, so
replace transparent_hugepage_active() to it, which is too heavy and
overkilling.

Link: https://lkml.kernel.org/r/20220513191705.457775-1-shy828301@gmail.com
Signed-off-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index de29821231c9b304ffc21cf3c979ba397bc95716..648cb3ce7099b46b4a4a7ed8204ed230715b1c97 100644 (file)
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -117,8 +117,10 @@ extern struct kobj_attribute shmem_enabled_attr;
 extern unsigned long transparent_hugepage_flags;
 
 static inline bool transhuge_vma_suitable(struct vm_area_struct *vma,
-               unsigned long haddr)
+               unsigned long addr)
 {
+       unsigned long haddr;
+
        /* Don't have to check pgoff for anonymous vma */
        if (!vma_is_anonymous(vma)) {
                if (!IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff,
@@ -126,6 +128,8 @@ static inline bool transhuge_vma_suitable(struct vm_area_struct *vma,
                        return false;
        }
 
+       haddr = addr & HPAGE_PMD_MASK;
+
        if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
                return false;
        return true;
@@ -342,7 +346,7 @@ static inline bool transparent_hugepage_active(struct vm_area_struct *vma)
 }
 
 static inline bool transhuge_vma_suitable(struct vm_area_struct *vma,
-               unsigned long haddr)
+               unsigned long addr)
 {
        return false;
 }

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index c10f839fc410ebe88ae30e10063898557f29cd15..e971a467fcdfaf320160435d9bbe135e6913e3fc 100644 (file)
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -243,7 +243,7 @@ restart:
                         * cleared *pmd but not decremented compound_mapcount().
                         */
                        if ((pvmw->flags & PVMW_SYNC) &&
-                           transparent_hugepage_active(vma) &&
+                           transhuge_vma_suitable(vma, pvmw->address) &&
                            (pvmw->nr_pages >= HPAGE_PMD_NR)) {
                                spinlock_t *ptl = pmd_lock(mm, pvmw->pmd);