The quilt patch titled
Subject: mm/gup: remove FOLL_SPLIT_PMD use of pmd_trans_unstable()
has been removed from the -mm tree. Its filename was
mm-gup-remove-foll_split_pmd-use-of-pmd_trans_unstable.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm/gup: remove FOLL_SPLIT_PMD use of pmd_trans_unstable()
Date: Thu, 8 Jun 2023 18:39:59 -0700 (PDT)
There is now no reason for follow_pmd_mask()'s FOLL_SPLIT_PMD block to
distinguish huge_zero_page from a normal THP: follow_page_pte() handles
any instability, and here it's a good idea to replace any pmd_none(*pmd)
by a page table a.s.a.p, in the huge_zero_page case as for a normal THP;
and this removes an unnecessary possibility of -EBUSY failure.
(Hmm, couldn't the normal THP case have hit an unstably refaulted THP
before? But there are only two, exceptional, users of FOLL_SPLIT_PMD.)
Link: https://lkml.kernel.org/r/59fd15dd-4d39-5ec-2043-1d5117f7f85@xxxxxxxxxx
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: SeongJae Park <sj@xxxxxxxxxx>
Cc: Song Liu <song@xxxxxxxxxx>
Cc: Steven Price <steven.price@xxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: Zack Rusin <zackr@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/gup.c | 19 ++++---------------
1 file changed, 4 insertions(+), 15 deletions(-)
--- a/mm/gup.c~mm-gup-remove-foll_split_pmd-use-of-pmd_trans_unstable
+++ a/mm/gup.c
@@ -682,21 +682,10 @@ static struct page *follow_pmd_mask(stru
return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
}
if (flags & FOLL_SPLIT_PMD) {
- int ret;
- page = pmd_page(*pmd);
- if (is_huge_zero_page(page)) {
- spin_unlock(ptl);
- ret = 0;
- split_huge_pmd(vma, pmd, address);
- if (pmd_trans_unstable(pmd))
- ret = -EBUSY;
- } else {
- spin_unlock(ptl);
- split_huge_pmd(vma, pmd, address);
- ret = pte_alloc(mm, pmd) ? -ENOMEM : 0;
- }
-
- return ret ? ERR_PTR(ret) :
+ spin_unlock(ptl);
+ split_huge_pmd(vma, pmd, address);
+ /* If pmd was left empty, stuff a page table in there quickly */
+ return pte_alloc(mm, pmd) ? ERR_PTR(-ENOMEM) :
follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
}
page = follow_trans_huge_pmd(vma, address, pmd, flags);
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
