Marking PMDs 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 pmd_special() check that can be
mislead, and most vm_normal_page_pmd()/vm_normal_folio_pmd() users that
would get this wrong right now are 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 use
folio_normal_page_pmd() in more places.
Fix it by teaching insert_pfn_pmd() to properly handle folios and
pfns -- moving refcount/mapcount/etc handling in there, renaming it to
insert_pmd(), and distinguishing between both cases using a new simple
"struct folio_or_pfn" structure.
Use folio_mk_pmd() to create a pmd for a folio cleanly.
Fixes: 6c88f72691f8 ("mm/huge_memory: add vmf_insert_folio_pmd()")
Reviewed-by: Jason Gunthorpe <j...@nvidia.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoa...@oracle.com>
Reviewed-by: Dan Williams <dan.j.willi...@intel.com>
Tested-by: Dan Williams <dan.j.willi...@intel.com>
Signed-off-by: David Hildenbrand <da...@redhat.com>
---
mm/huge_memory.c | 59 ++++++++++++++++++++++++++++++++----------------
1 file changed, 40 insertions(+), 19 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 49b98082c5401..d1e3e253c714a 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1372,9 +1372,17 @@ vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault
*vmf)
return __do_huge_pmd_anonymous_page(vmf);
}
-static int insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
- pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
- pgtable_t pgtable)
+struct folio_or_pfn {
+ union {
+ struct folio *folio;
+ pfn_t pfn;
+ };
+ bool is_folio;
+};
+
+static int insert_pmd(struct vm_area_struct *vma, unsigned long addr,
+ pmd_t *pmd, struct folio_or_pfn fop, pgprot_t prot,
+ bool write, pgtable_t pgtable)
{
struct mm_struct *mm = vma->vm_mm;
pmd_t entry;
@@ -1382,8 +1390,11 @@ static int insert_pfn_pmd(struct vm_area_struct *vma,
unsigned long addr,
lockdep_assert_held(pmd_lockptr(mm, pmd));
if (!pmd_none(*pmd)) {
+ const unsigned long pfn = fop.is_folio ? folio_pfn(fop.folio) :
+ pfn_t_to_pfn(fop.pfn);
+
if (write) {
- if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
+ if (pmd_pfn(*pmd) != pfn) {
WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
return -EEXIST;
}
@@ -1396,11 +1407,20 @@ static int insert_pfn_pmd(struct vm_area_struct *vma,
unsigned long addr,
return -EEXIST;
}
- entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
- if (pfn_t_devmap(pfn))
- entry = pmd_mkdevmap(entry);
- else
- entry = pmd_mkspecial(entry);
+ if (fop.is_folio) {
+ entry = folio_mk_pmd(fop.folio, vma->vm_page_prot);
+
+ folio_get(fop.folio);
+ folio_add_file_rmap_pmd(fop.folio, &fop.folio->page, vma);
+ add_mm_counter(mm, mm_counter_file(fop.folio), HPAGE_PMD_NR);
+ } else {
+ entry = pmd_mkhuge(pfn_t_pmd(fop.pfn, prot));
+
+ if (pfn_t_devmap(fop.pfn))
+ entry = pmd_mkdevmap(entry);
+ else
+ entry = pmd_mkspecial(entry);
+ }
if (write) {
entry = pmd_mkyoung(pmd_mkdirty(entry));
entry = maybe_pmd_mkwrite(entry, vma);
@@ -1431,6 +1451,9 @@ vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t
pfn, bool write)
unsigned long addr = vmf->address & PMD_MASK;
struct vm_area_struct *vma = vmf->vma;
pgprot_t pgprot = vma->vm_page_prot;
+ struct folio_or_pfn fop = {
+ .pfn = pfn,
+ };
pgtable_t pgtable = NULL;
spinlock_t *ptl;
int error;
@@ -1458,8 +1481,8 @@ vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t
pfn, bool write)
pfnmap_setup_cachemode_pfn(pfn_t_to_pfn(pfn), &pgprot);
ptl = pmd_lock(vma->vm_mm, vmf->pmd);
- error = insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write,
- pgtable);
+ error = insert_pmd(vma, addr, vmf->pmd, fop, pgprot, write,
+ pgtable);
spin_unlock(ptl);
if (error && pgtable)
pte_free(vma->vm_mm, pgtable);
@@ -1474,6 +1497,10 @@ vm_fault_t vmf_insert_folio_pmd(struct vm_fault *vmf,
struct folio *folio,
struct vm_area_struct *vma = vmf->vma;
unsigned long addr = vmf->address & PMD_MASK;
struct mm_struct *mm = vma->vm_mm;
+ struct folio_or_pfn fop = {
+ .folio = folio,
+ .is_folio = true,
+ };
spinlock_t *ptl;
pgtable_t pgtable = NULL;
int error;
@@ -1491,14 +1518,8 @@ vm_fault_t vmf_insert_folio_pmd(struct vm_fault *vmf,
struct folio *folio,
}
ptl = pmd_lock(mm, vmf->pmd);
- if (pmd_none(*vmf->pmd)) {
- folio_get(folio);
- folio_add_file_rmap_pmd(folio, &folio->page, vma);
- add_mm_counter(mm, mm_counter_file(folio), HPAGE_PMD_NR);
- }
- error = insert_pfn_pmd(vma, addr, vmf->pmd,
- pfn_to_pfn_t(folio_pfn(folio)), vma->vm_page_prot,
- write, pgtable);
+ error = insert_pmd(vma, addr, vmf->pmd, fop, vma->vm_page_prot,
+ write, pgtable);
spin_unlock(ptl);
if (error && pgtable)
pte_free(mm, pgtable);
--
2.49.0
