The quilt patch titled
Subject: mm/migrate_device: allow pte_offset_map_lock() to fail
has been removed from the -mm tree. Its filename was
mm-migrate_device-allow-pte_offset_map_lock-to-fail.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/migrate_device: allow pte_offset_map_lock() to fail
Date: Thu, 8 Jun 2023 18:38:17 -0700 (PDT)
migrate_vma_collect_pmd(): remove the pmd_trans_unstable() handling after
splitting huge zero pmd, and the pmd_none() handling after successfully
splitting huge page: those are now managed inside pte_offset_map_lock(),
and by "goto again" when it fails.
But the skip after unsuccessful split_huge_page() must stay: it avoids an
endless loop. The skip when pmd_bad()? Remove that: it will be treated
as a hole rather than a skip once cleared by pte_offset_map_lock(), but
with different timing that would be so anyway; and it's arguably best to
leave the pmd_bad() handling centralized there.
migrate_vma_insert_page(): remove comment on the old pte_offset_map() and
old locking limitations; remove the pmd_trans_unstable() check and just
proceed to pte_offset_map_lock(), aborting when it fails (page has been
charged to memcg, but as in other cases, it's uncharged when freed).
Link: https://lkml.kernel.org/r/1131be62-2e84-da2f-8f45-807b2cbeeec5@xxxxxxxxxx
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Reviewed-by: 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: Yang Shi <shy828301@xxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: Zack Rusin <zackr@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/migrate_device.c | 31 ++++---------------------------
1 file changed, 4 insertions(+), 27 deletions(-)
--- a/mm/migrate_device.c~mm-migrate_device-allow-pte_offset_map_lock-to-fail
+++ a/mm/migrate_device.c
@@ -83,9 +83,6 @@ again:
if (is_huge_zero_page(page)) {
spin_unlock(ptl);
split_huge_pmd(vma, pmdp, addr);
- if (pmd_trans_unstable(pmdp))
- return migrate_vma_collect_skip(start, end,
- walk);
} else {
int ret;
@@ -100,16 +97,12 @@ again:
if (ret)
return migrate_vma_collect_skip(start, end,
walk);
- if (pmd_none(*pmdp))
- return migrate_vma_collect_hole(start, end, -1,
- walk);
}
}
- if (unlikely(pmd_bad(*pmdp)))
- return migrate_vma_collect_skip(start, end, walk);
-
ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
+ if (!ptep)
+ goto again;
arch_enter_lazy_mmu_mode();
for (; addr < end; addr += PAGE_SIZE, ptep++) {
@@ -595,27 +588,10 @@ static void migrate_vma_insert_page(stru
pmdp = pmd_alloc(mm, pudp, addr);
if (!pmdp)
goto abort;
-
if (pmd_trans_huge(*pmdp) || pmd_devmap(*pmdp))
goto abort;
-
- /*
- * Use pte_alloc() instead of pte_alloc_map(). We can't run
- * pte_offset_map() on pmds where a huge pmd might be created
- * from a different thread.
- *
- * pte_alloc_map() is safe to use under mmap_write_lock(mm) or when
- * parallel threads are excluded by other means.
- *
- * Here we only have mmap_read_lock(mm).
- */
if (pte_alloc(mm, pmdp))
goto abort;
-
- /* See the comment in pte_alloc_one_map() */
- if (unlikely(pmd_trans_unstable(pmdp)))
- goto abort;
-
if (unlikely(anon_vma_prepare(vma)))
goto abort;
if (mem_cgroup_charge(page_folio(page), vma->vm_mm, GFP_KERNEL))
@@ -650,7 +626,8 @@ static void migrate_vma_insert_page(stru
}
ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);
-
+ if (!ptep)
+ goto abort;
if (check_stable_address_space(mm))
goto unlock_abort;
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
