mm/gup: handle huge pud for follow_pud_mask()

Teach follow_pud_mask() to be able to handle normal PUD pages like
hugetlb.

Rename follow_devmap_pud() to follow_huge_pud() so that it can process
either huge devmap or hugetlb.  Move it out of TRANSPARENT_HUGEPAGE_PUD
and and huge_memory.c (which relies on CONFIG_THP).  Switch to pud_leaf()
to detect both cases in the slow gup.

In the new follow_huge_pud(), taking care of possible CoR for hugetlb if
necessary.  touch_pud() needs to be moved out of huge_memory.c to be
accessable from gup.c even if !THP.

Since at it, optimize the non-present check by adding a pud_present()
early check before taking the pgtable lock, failing the follow_page()
early if PUD is not present: that is required by both devmap or hugetlb. 
Use pud_huge() to also cover the pud_devmap() case.

One more trivial thing to mention is, introduce "pud_t pud" in the code
paths along the way, so the code doesn't dereference *pudp multiple time. 
Not only because that looks less straightforward, but also because if the
dereference really happened, it's not clear whether there can be race to
see different *pudp values when it's being modified at the same time.

Setting ctx->page_mask properly for a PUD entry.  As a side effect, this
patch should also be able to optimize devmap GUP on PUD to be able to jump
over the whole PUD range, but not yet verified.  Hugetlb already can do so
prior to this patch.

Link: https://lkml.kernel.org/r/20240327152332.950956-11-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, 0 insertions, 8 deletions

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index ff72ee19a125..ab26d9e65ec3 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -351,8 +351,6 @@ static inline bool folio_test_pmd_mappable(struct folio *folio)
 
 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
 		pmd_t *pmd, int flags, struct dev_pagemap **pgmap);
-struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
-		pud_t *pud, int flags, struct dev_pagemap **pgmap);
 
 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf);
 
@@ -507,12 +505,6 @@ static inline struct page *follow_devmap_pmd(struct vm_area_struct *vma,
 	return NULL;
 }
 
-static inline struct page *follow_devmap_pud(struct vm_area_struct *vma,
-	unsigned long addr, pud_t *pud, int flags, struct dev_pagemap **pgmap)
-{
-	return NULL;
-}
-
 static inline bool thp_migration_supported(void)
 {
 	return false;