github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-30 01:53:29 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

mm/huge_memory: don't mark refcounted folios special in vmf_insert_folio_pud()

Browse Source 
Marking PUDs that map a "normal" refcounted folios as special is against
our rules documented for vm_normal_page().  normal (refcounted) folios
shall never have the page table mapping marked as special.

Fortunately, there are not that many pud_special() check that can be
mislead and are right now rather harmless: e.g., none so far bases
decisions whether to grab a folio reference on that decision.

Well, and GUP-fast will fallback to GUP-slow.  All in all, so far no big
implications as it seems.

Getting this right will get more important as we introduce
folio_normal_page_pud() and start using it in more place where we
currently special-case based on other VMA flags.

Fix it just like we fixed vmf_insert_folio_pmd().

Add folio_mk_pud() to mimic what we do with folio_mk_pmd().

Link: https://lkml.kernel.org/r/20250613092702.1943533-4-david@redhat.com
Fixes: dbe5415329 ("mm/huge_memory: add vmf_insert_folio_pud()")
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Tested-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Mariano Pache <npache@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2025-06-13 11:27:02 +02:00 committed by Andrew Morton
parent c4297465d4
commit 02825c0925
2 changed files with 47 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
include/linux/mm.h
View File

@ -1816,7 +1816,24 @@ static inline pmd_t folio_mk_pmd(struct folio *folio, pgprot_t pgprot)
{
return pmd_mkhuge(pfn_pmd(folio_pfn(folio), pgprot));
}
#endif
#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
/**
* folio_mk_pud - Create a PUD for this folio
* @folio: The folio to create a PUD for
* @pgprot: The page protection bits to use
*
* Create a page table entry for the first page of this folio.
* This is suitable for passing to set_pud_at().
*
* Return: A page table entry suitable for mapping this folio.
*/
static inline pud_t folio_mk_pud(struct folio *folio, pgprot_t pgprot)
{
return pud_mkhuge(pfn_pud(folio_pfn(folio), pgprot));
}
#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
#endif /* CONFIG_MMU */
static inline bool folio_has_pincount(const struct folio *folio)

52
mm/huge_memory.c
View File

@ -1536,15 +1536,18 @@ static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
return pud;
}
static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
static void insert_pud(struct vm_area_struct *vma, unsigned long addr,
pud_t *pud, struct folio_or_pfn fop, pgprot_t prot, bool write)
{
struct mm_struct *mm = vma->vm_mm;
pud_t entry;
if (!pud_none(*pud)) {
const unsigned long pfn = fop.is_folio ? folio_pfn(fop.folio) :
pfn_t_to_pfn(fop.pfn);
if (write) {
if (WARN_ON_ONCE(pud_pfn(*pud) != pfn_t_to_pfn(pfn)))
if (WARN_ON_ONCE(pud_pfn(*pud) != pfn))
return;
entry = pud_mkyoung(*pud);
entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
@ -1554,11 +1557,20 @@ static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
return;
}
entry = pud_mkhuge(pfn_t_pud(pfn, prot));
if (pfn_t_devmap(pfn))
entry = pud_mkdevmap(entry);
else
entry = pud_mkspecial(entry);
if (fop.is_folio) {
entry = folio_mk_pud(fop.folio, vma->vm_page_prot);
folio_get(fop.folio);
folio_add_file_rmap_pud(fop.folio, &fop.folio->page, vma);
add_mm_counter(mm, mm_counter_file(fop.folio), HPAGE_PUD_NR);
} else {
entry = pud_mkhuge(pfn_t_pud(fop.pfn, prot));
if (pfn_t_devmap(fop.pfn))
entry = pud_mkdevmap(entry);
else
entry = pud_mkspecial(entry);
}
if (write) {
entry = pud_mkyoung(pud_mkdirty(entry));
entry = maybe_pud_mkwrite(entry, vma);
@ -1582,6 +1594,9 @@ vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write)
unsigned long addr = vmf->address & PUD_MASK;
struct vm_area_struct *vma = vmf->vma;
pgprot_t pgprot = vma->vm_page_prot;
struct folio_or_pfn fop = {
.pfn = pfn,
};
spinlock_t *ptl;
/*
@ -1601,7 +1616,7 @@ vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write)
pfnmap_setup_cachemode_pfn(pfn_t_to_pfn(pfn), &pgprot);
ptl = pud_lock(vma->vm_mm, vmf->pud);
insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write);
insert_pud(vma, addr, vmf->pud, fop, pgprot, write);
spin_unlock(ptl);
return VM_FAULT_NOPAGE;
@ -1623,6 +1638,10 @@ vm_fault_t vmf_insert_folio_pud(struct vm_fault *vmf, struct folio *folio,
unsigned long addr = vmf->address & PUD_MASK;
pud_t *pud = vmf->pud;
struct mm_struct *mm = vma->vm_mm;
struct folio_or_pfn fop = {
.folio = folio,
.is_folio = true,
};
spinlock_t *ptl;
if (addr < vma->vm_start || addr >= vma->vm_end)
@ -1632,20 +1651,7 @@ vm_fault_t vmf_insert_folio_pud(struct vm_fault *vmf, struct folio *folio,
return VM_FAULT_SIGBUS;
ptl = pud_lock(mm, pud);
/*
* If there is already an entry present we assume the folio is
* already mapped, hence no need to take another reference. We
* still call insert_pfn_pud() though in case the mapping needs
* upgrading to writeable.
*/
if (pud_none(*vmf->pud)) {
folio_get(folio);
folio_add_file_rmap_pud(folio, &folio->page, vma);
add_mm_counter(mm, mm_counter_file(folio), HPAGE_PUD_NR);
}
insert_pfn_pud(vma, addr, vmf->pud, pfn_to_pfn_t(folio_pfn(folio)),
vma->vm_page_prot, write);
insert_pud(vma, addr, vmf->pud, fop, vma->vm_page_prot, write);
spin_unlock(ptl);
return VM_FAULT_NOPAGE;