[PATCH RFC 08/12] mm/gup: Handle hugetlb for no_page_table()

Peter Xu
2023-11-16T01:29:57Z

no_page_table() is not yet used for hugetlb code paths. Make it prepared.

The major difference here is hugetlb will return -EFAULT as long as page
cache does not exist, even if VM_SHARED. See hugetlb_follow_page_mask().

Pass "address" into no_page_table() too, as hugetlb will need it.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
mm/gup.c | 40 ++++++++++++++++++++++++----------------
1 file changed, 24 insertions(+), 16 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 69dae51f3eb1..89c1584d68f0 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -501,19 +501,27 @@ static inline void mm_set_has_pinned_flag(unsigned long *mm_flags)

#ifdef CONFIG_MMU
static struct page *no_page_table(struct vm_area_struct *vma,
- unsigned int flags)
+ unsigned int flags, unsigned long address)
{
+ if (!(flags & FOLL_DUMP))
+ return NULL;
+
/*
- * When core dumping an enormous anonymous area that nobody
- * has touched so far, we don't want to allocate unnecessary pages or
+ * When core dumping, we don't want to allocate unnecessary pages or
* page tables. Return error instead of NULL to skip handle_mm_fault,
* then get_dump_page() will return NULL to leave a hole in the dump.
* But we can only make this optimization where a hole would surely
* be zero-filled if handle_mm_fault() actually did handle it.
*/
- if ((flags & FOLL_DUMP) &&
- (vma_is_anonymous(vma) || !vma->vm_ops->fault))
+ if (is_vm_hugetlb_page(vma)) {
+ struct hstate *h = hstate_vma(vma);
+
+ if (!hugetlbfs_pagecache_present(h, vma, address))
+ return ERR_PTR(-EFAULT);
+ } else if ((vma_is_anonymous(vma) || !vma->vm_ops->fault)) {
return ERR_PTR(-EFAULT);
+ }
+
return NULL;
}

@@ -593,7 +601,7 @@ static struct page *follow_page_pte(struct vm_area_struct *vma,

ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
if (!ptep)
- return no_page_table(vma, flags);
+ return no_page_table(vma, flags, address);
pte = ptep_get(ptep);
if (!pte_present(pte))
goto no_page;
@@ -685,7 +693,7 @@ static struct page *follow_page_pte(struct vm_area_struct *vma,
pte_unmap_unlock(ptep, ptl);
if (!pte_none(pte))
return NULL;
- return no_page_table(vma, flags);
+ return no_page_table(vma, flags, address);
}

static struct page *follow_pmd_mask(struct vm_area_struct *vma,
@@ -701,9 +709,9 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma,
pmd = pmd_offset(pudp, address);
pmdval = pmdp_get_lockless(pmd);
if (pmd_none(pmdval))
- return no_page_table(vma, flags);
+ return no_page_table(vma, flags, address);
if (!pmd_present(pmdval))
- return no_page_table(vma, flags);
+ return no_page_table(vma, flags, address);
if (pmd_devmap(pmdval)) {
ptl = pmd_lock(mm, pmd);
page = follow_devmap_pmd(vma, address, pmd, flags, &ctx->pgmap);
@@ -714,12 +722,12 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma,
return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);

if (pmd_protnone(pmdval) && !gup_can_follow_protnone(vma, flags))
- return no_page_table(vma, flags);
+ return no_page_table(vma, flags, address);

ptl = pmd_lock(mm, pmd);
if (unlikely(!pmd_present(*pmd))) {
spin_unlock(ptl);
- return no_page_table(vma, flags);
+ return no_page_table(vma, flags, address);
}
if (unlikely(!pmd_trans_huge(*pmd))) {
spin_unlock(ptl);
@@ -750,7 +758,7 @@ static struct page *follow_pud_mask(struct vm_area_struct *vma,

pud = pud_offset(p4dp, address);
if (pud_none(*pud))
- return no_page_table(vma, flags);
+ return no_page_table(vma, flags, address);
if (pud_devmap(*pud)) {
ptl = pud_lock(mm, pud);
page = follow_devmap_pud(vma, address, pud, flags, &ctx->pgmap);
@@ -758,7 +766,7 @@ static struct page *follow_pud_mask(struct vm_area_struct *vma,
return page;
}
if (unlikely(pud_bad(*pud)))
- return no_page_table(vma, flags);
+ return no_page_table(vma, flags, address);

return follow_pmd_mask(vma, address, pud, flags, ctx);
}
@@ -772,10 +780,10 @@ static struct page *follow_p4d_mask(struct vm_area_struct *vma,

p4d = p4d_offset(pgdp, address);
if (p4d_none(*p4d))
- return no_page_table(vma, flags);
+ return no_page_table(vma, flags, address);
BUILD_BUG_ON(p4d_huge(*p4d));
if (unlikely(p4d_bad(*p4d)))
- return no_page_table(vma, flags);
+ return no_page_table(vma, flags, address);

return follow_pud_mask(vma, address, p4d, flags, ctx);
}
@@ -825,7 +833,7 @@ static struct page *follow_page_mask(struct vm_area_struct *vma,
pgd = pgd_offset(mm, address);

if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
- return no_page_table(vma, flags);
+ return no_page_table(vma, flags, address);

return follow_p4d_mask(vma, address, pgd, flags, ctx);
}
--
2.41.0