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

Bugzilla: https://bugzilla.redhat.com/2160210

commit c453d8c7d1384d7e1d7f26d3ec0d527092edf801
Author: Yang Shi <shy828301@gmail.com>
Date:   Fri May 13 12:17:05 2022 -0700

    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>

Signed-off-by: Chris von Recklinghausen <crecklin@redhat.com>
This commit is contained in:
Chris von Recklinghausen 2023-03-24 07:44:17 -04:00
parent adb476da52
commit bb6be8680b
2 changed files with 7 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
include/linux/huge_mm.h
View File

@ -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;
}

2
mm/page_vma_mapped.c
View File

@ -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);