* [PATCH v3] mm/thp: fix __split_huge_pmd_locked() for migration PMD
@ 2020-09-03 18:31 Ralph Campbell
2020-09-06 3:16 ` Sasha Levin
0 siblings, 1 reply; 2+ messages in thread
From: Ralph Campbell @ 2020-09-03 18:31 UTC (permalink / raw)
To: linux-mm, nouveau, linux-kselftest, linux-kernel
Cc: Jerome Glisse, John Hubbard, Alistair Popple, Christoph Hellwig,
Jason Gunthorpe, Bharata B Rao, Ben Skeggs, Shuah Khan,
Andrew Morton, Ralph Campbell, stable, Yang Shi, Zi Yan
A migrating transparent huge page has to already be unmapped. Otherwise,
the page could be modified while it is being copied to a new page and
data could be lost. The function __split_huge_pmd() checks for a PMD
migration entry before calling __split_huge_pmd_locked() leading one to
think that __split_huge_pmd_locked() can handle splitting a migrating PMD.
However, the code always increments the page->_mapcount and adjusts the
memory control group accounting assuming the page is mapped.
Also, if the PMD entry is a migration PMD entry, the call to
is_huge_zero_pmd(*pmd) is incorrect because it calls pmd_pfn(pmd) instead
of migration_entry_to_pfn(pmd_to_swp_entry(pmd)).
Fix these problems by checking for a PMD migration entry.
Fixes: 84c3fc4e9c56 ("mm: thp: check pmd migration entry in common path")
cc: stable@vger.kernel.org # 4.14+
Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
---
No changes in v3 to this patch, just added reviewed-by and fixes to the
change log and sending this as a separate patch from the rest of the
series ("mm/hmm/nouveau: add THP migration to migrate_vma_*").
I'll hold off resending the series without this patch unless there are
changes needed.
mm/huge_memory.c | 42 +++++++++++++++++++++++-------------------
1 file changed, 23 insertions(+), 19 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 2a468a4acb0a..606d712d9505 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2023,7 +2023,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
put_page(page);
add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
return;
- } else if (is_huge_zero_pmd(*pmd)) {
+ } else if (pmd_trans_huge(*pmd) && is_huge_zero_pmd(*pmd)) {
/*
* FIXME: Do we want to invalidate secondary mmu by calling
* mmu_notifier_invalidate_range() see comments below inside
@@ -2117,30 +2117,34 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
pte = pte_offset_map(&_pmd, addr);
BUG_ON(!pte_none(*pte));
set_pte_at(mm, addr, pte, entry);
- atomic_inc(&page[i]._mapcount);
- pte_unmap(pte);
- }
-
- /*
- * Set PG_double_map before dropping compound_mapcount to avoid
- * false-negative page_mapped().
- */
- if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
- for (i = 0; i < HPAGE_PMD_NR; i++)
+ if (!pmd_migration)
atomic_inc(&page[i]._mapcount);
+ pte_unmap(pte);
}
- lock_page_memcg(page);
- if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
- /* Last compound_mapcount is gone. */
- __dec_lruvec_page_state(page, NR_ANON_THPS);
- if (TestClearPageDoubleMap(page)) {
- /* No need in mapcount reference anymore */
+ if (!pmd_migration) {
+ /*
+ * Set PG_double_map before dropping compound_mapcount to avoid
+ * false-negative page_mapped().
+ */
+ if (compound_mapcount(page) > 1 &&
+ !TestSetPageDoubleMap(page)) {
for (i = 0; i < HPAGE_PMD_NR; i++)
- atomic_dec(&page[i]._mapcount);
+ atomic_inc(&page[i]._mapcount);
+ }
+
+ lock_page_memcg(page);
+ if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
+ /* Last compound_mapcount is gone. */
+ __dec_lruvec_page_state(page, NR_ANON_THPS);
+ if (TestClearPageDoubleMap(page)) {
+ /* No need in mapcount reference anymore */
+ for (i = 0; i < HPAGE_PMD_NR; i++)
+ atomic_dec(&page[i]._mapcount);
+ }
}
+ unlock_page_memcg(page);
}
- unlock_page_memcg(page);
smp_wmb(); /* make pte visible before pmd */
pmd_populate(mm, pmd, pgtable);
--
2.20.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v3] mm/thp: fix __split_huge_pmd_locked() for migration PMD
2020-09-03 18:31 [PATCH v3] mm/thp: fix __split_huge_pmd_locked() for migration PMD Ralph Campbell
@ 2020-09-06 3:16 ` Sasha Levin
0 siblings, 0 replies; 2+ messages in thread
From: Sasha Levin @ 2020-09-06 3:16 UTC (permalink / raw)
To: Sasha Levin, Ralph Campbell, linux-mm, nouveau
Cc: Jerome Glisse, John Hubbard, stable
Hi
[This is an automated email]
This commit has been processed because it contains a "Fixes:" tag
fixing commit: 84c3fc4e9c56 ("mm: thp: check pmd migration entry in common path").
The bot has tested the following trees: v5.8.6, v5.4.62, v4.19.143, v4.14.196.
v5.8.6: Build OK!
v5.4.62: Failed to apply! Possible dependencies:
0d1c20722ab3 ("mm: memcontrol: switch to native NR_FILE_PAGES and NR_SHMEM counters")
3fba69a56e16 ("mm: memcontrol: drop @compound parameter from memcg charging API")
468c398233da ("mm: memcontrol: switch to native NR_ANON_THPS counter")
72981e0e7b60 ("userfaultfd: wp: add UFFDIO_COPY_MODE_WP")
83d116c53058 ("mm: fix double page fault on arm64 if PTE_AF is cleared")
85b9f46e8ea4 ("mm, thp: track fallbacks due to failed memcg charges separately")
92855270ff08 ("mm/memcontrol.c: cleanup some useless code")
be5d0a74c62d ("mm: memcontrol: switch to native NR_ANON_MAPPED counter")
c23a0c99793f ("mm/migrate: clean up some minor coding style")
dcdf11ee1441 ("mm, shmem: add vmstat for hugepage fallback")
f4129ea3591a ("mm: fix NUMA node file count error in replace_page_cache()")
ffe945e633b5 ("khugepaged: do not stop collapse if less than half PTEs are referenced")
v4.19.143: Failed to apply! Possible dependencies:
0ac261042084 ("x86/irq/64: Init hardirq_stack_ptr during CPU hotplug")
0d1c20722ab3 ("mm: memcontrol: switch to native NR_FILE_PAGES and NR_SHMEM counters")
117ed4548541 ("x86/irq/64: Remove stack overflow debug code")
231c4846b106 ("x86/irq/32: Make irq stack a character array")
30842211506e ("x86/exceptions: Remove unused stack defines on 32bit")
39656e83dab9 ("mm: lift the x86_32 PAE version of gup_get_pte to common code")
468c398233da ("mm: memcontrol: switch to native NR_ANON_THPS counter")
4f44b8f0b33b ("x86/irq/64: Remove a hardcoded irq_stack_union access")
66c7ceb47f62 ("x86/irq/32: Handle irq stack allocation failure proper")
758a2e312228 ("x86/irq/64: Rename irq_stack_ptr to hardirq_stack_ptr")
7ac870747988 ("x86/vdso: Switch to generic vDSO implementation")
99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS")
a754fe2b76d1 ("x86/irq/32: Rename hard/softirq_stack to hard/softirq_stack_ptr")
aa641c287b2f ("x86/irq/32: Define IRQ_STACK_SIZE")
be5d0a74c62d ("mm: memcontrol: switch to native NR_ANON_MAPPED counter")
df835e7083be ("x86/irq/64: Sanitize the top/bottom confusion")
e6401c130931 ("x86/irq/64: Split the IRQ stack into its own pages")
v4.14.196: Failed to apply! Possible dependencies:
050e9baa9dc9 ("Kbuild: rename CC_STACKPROTECTOR[_STRONG] config variables")
0d1c20722ab3 ("mm: memcontrol: switch to native NR_FILE_PAGES and NR_SHMEM counters")
117ed4548541 ("x86/irq/64: Remove stack overflow debug code")
152e93af3cfe ("mm, thp: Do not make pmd/pud dirty without a reason")
2a61f4747eea ("stack-protector: test compiler capability in Kconfig and drop AUTO mode")
2b8383927525 ("Makefile: move stack-protector compiler breakage test earlier")
2bc2f688fdf8 ("Makefile: move stack-protector availability out of Kconfig")
39656e83dab9 ("mm: lift the x86_32 PAE version of gup_get_pte to common code")
44c6dc940b19 ("Makefile: introduce CONFIG_CC_STACKPROTECTOR_AUTO")
4645b9fe84bf ("mm/mmu_notifier: avoid call to invalidate_range() in range_end()")
468c398233da ("mm: memcontrol: switch to native NR_ANON_THPS counter")
59c66c5f8c4f ("mm: factor out page cache page freeing into a separate function")
5ecc4d852c03 ("mm: factor out checks and accounting from __delete_from_page_cache()")
76253fbc8fbf ("mm: move accounting updates before page_cache_tree_delete()")
7ac870747988 ("x86/vdso: Switch to generic vDSO implementation")
8373b7d9d174 ("Documentation: kconfig: add recommended way to describe compiler support")
99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS")
be5d0a74c62d ("mm: memcontrol: switch to native NR_ANON_MAPPED counter")
e6401c130931 ("x86/irq/64: Split the IRQ stack into its own pages")
fadae2953072 ("thp: use mm_file_counter to determine update which rss counter")
NOTE: The patch will not be queued to stable trees until it is upstream.
How should we proceed with this patch?
--
Thanks
Sasha
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