mm/gup: handle huge pmd for follow_pmd_mask()

Replace pmd_trans_huge() with pmd_leaf() to also cover pmd_huge() as long
as enabled.

FOLL_TOUCH and FOLL_SPLIT_PMD only apply to THP, not yet huge.

Since now follow_trans_huge_pmd() can process hugetlb pages, renaming it
into follow_huge_pmd() to match what it does.  Move it into gup.c so not
depend on CONFIG_THP.

When at it, move the ctx->page_mask setup into follow_huge_pmd(), only set
it when the page is valid.  It was not a bug to set it before even if GUP
failed (page==NULL), because follow_page_mask() callers always ignores
page_mask if so.  But doing so makes the code cleaner.

[peterx@redhat.com: allow follow_pmd_mask() to take hugetlb tail pages]
  Link: https://lkml.kernel.org/r/20240403013249.1418299-3-peterx@redhat.com
Link: https://lkml.kernel.org/r/20240327152332.950956-12-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Tested-by: Ryan Roberts <ryan.roberts@arm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrew Jones <andrew.jones@linux.dev>
Cc: Aneesh Kumar K.V (IBM) <aneesh.kumar@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Mike Rapoport (IBM)" <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 2 insertions, 84 deletions

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 249318f367e4..157cee64850c 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1221,8 +1221,8 @@ vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write)
 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
 
-static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
-		      pmd_t *pmd, bool write)
+void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
+	       pmd_t *pmd, bool write)
 {
 	pmd_t _pmd;
 
@@ -1577,88 +1577,6 @@ static inline bool can_change_pmd_writable(struct vm_area_struct *vma,
 	return pmd_dirty(pmd);
 }
 
-/* FOLL_FORCE can write to even unwritable PMDs in COW mappings. */
-static inline bool can_follow_write_pmd(pmd_t pmd, struct page *page,
-					struct vm_area_struct *vma,
-					unsigned int flags)
-{
-	/* If the pmd is writable, we can write to the page. */
-	if (pmd_write(pmd))
-		return true;
-
-	/* Maybe FOLL_FORCE is set to override it? */
-	if (!(flags & FOLL_FORCE))
-		return false;
-
-	/* But FOLL_FORCE has no effect on shared mappings */
-	if (vma->vm_flags & (VM_MAYSHARE | VM_SHARED))
-		return false;
-
-	/* ... or read-only private ones */
-	if (!(vma->vm_flags & VM_MAYWRITE))
-		return false;
-
-	/* ... or already writable ones that just need to take a write fault */
-	if (vma->vm_flags & VM_WRITE)
-		return false;
-
-	/*
-	 * See can_change_pte_writable(): we broke COW and could map the page
-	 * writable if we have an exclusive anonymous page ...
-	 */
-	if (!page || !PageAnon(page) || !PageAnonExclusive(page))
-		return false;
-
-	/* ... and a write-fault isn't required for other reasons. */
-	if (vma_soft_dirty_enabled(vma) && !pmd_soft_dirty(pmd))
-		return false;
-	return !userfaultfd_huge_pmd_wp(vma, pmd);
-}
-
-struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
-				   unsigned long addr,
-				   pmd_t *pmd,
-				   unsigned int flags)
-{
-	struct mm_struct *mm = vma->vm_mm;
-	struct page *page;
-	int ret;
-
-	assert_spin_locked(pmd_lockptr(mm, pmd));
-
-	page = pmd_page(*pmd);
-	VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
-
-	if ((flags & FOLL_WRITE) &&
-	    !can_follow_write_pmd(*pmd, page, vma, flags))
-		return NULL;
-
-	/* Avoid dumping huge zero page */
-	if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
-		return ERR_PTR(-EFAULT);
-
-	if (pmd_protnone(*pmd) && !gup_can_follow_protnone(vma, flags))
-		return NULL;
-
-	if (!pmd_write(*pmd) && gup_must_unshare(vma, flags, page))
-		return ERR_PTR(-EMLINK);
-
-	VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) &&
-			!PageAnonExclusive(page), page);
-
-	ret = try_grab_page(page, flags);
-	if (ret)
-		return ERR_PTR(ret);
-
-	if (flags & FOLL_TOUCH)
-		touch_pmd(vma, addr, pmd, flags & FOLL_WRITE);
-
-	page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
-	VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
-
-	return page;
-}
-
 /* NUMA hinting page fault entry point for trans huge pmds */
 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
 {