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 de29821..648cb3c 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 c10f839..e971a46 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);