From: "David Hildenbrand (Arm)" <david@kernel.org>
To: "Gregory Price (Meta)" <gourry@gourry.net>
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Chris Mason <mason@kernel.org>,
stable@vger.kernel.org
Subject: Re: [PATCH v2 14/47] mm/huge_memory: fix zapping migration entries for device-private THPs
Date: Fri, 30 Oct 2026 12:10:47 +0100 [thread overview]
Message-ID: <ef51420b-0260-454f-b08b-f4e5a3da6e20@kernel.org> (raw)
In-Reply-To: <179331304801.2127828.6570375349219520262.b4-reply@b4>
On 10/29/26 23:30, Gregory Price (Meta) wrote:
> On 2026-10-29 21:33 +0100, David Hildenbrand (Arm) wrote:
>> From: Chris Mason <mason@kernel.org>
>>
>> A PMD migration entry can refer to a device-private folio.
>> zap_huge_pmd_folio() checks the folio type instead of the entry type,
>> so it treats such a migration entry as a device-private entry.
>>
>> Installing the migration entry already removed the reverse mapping and
>> dropped the mapping reference. Zapping it must not repeat those
>> operations. Concurrent MADV_DONTNEED during migration back to system
>> memory can trigger this.
>>
>> Check the PMD entry type using pmd_is_device_private_entry().
>>
>> Fix generated by an LLM and sent by Chris Mason in private.
>>
>> Fixes: 368076f52ebe ("mm/huge_memory: add device-private THP support to PMD operations")
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Chris Mason <mason@kernel.org>
>> [ david: simplify description ]
>> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
>
> One note below, but it's not a holdup.
>
> Reviewed-by: Gregory Price (Meta) <gourry@gourry.net>
>
>> + const bool is_device_private = !is_present && pmd_is_device_private_entry(pmdval);
>
> pmd_is_device_private_entry() already returns false for a present
> pmdval - so !is_present is redundant. If there was a reason to open
> code this, then keep it, but otherwise you could drop it.
Ah, softleaf_from_pmd() takes care of that. Yes, let me drop the is_present check.
(I'll double check that both are guaranteed to be consistent; but otherwise we
might have a bug already)
--
Cheers,
David
next prev parent reply other threads:[~2026-10-30 11:11 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-29 20:32 [PATCH v2 00/47] mm: various (urgent?) fixes David Hildenbrand (Arm)
2026-10-29 20:32 ` [PATCH v2 01/47] mm/mglru: don't use stack pointers when walking PUD and PMD tables David Hildenbrand (Arm)
2026-10-30 0:20 ` SJ Park
2026-10-30 10:21 ` David Hildenbrand (Arm)
2026-10-29 20:32 ` [PATCH v2 02/47] fork: take mmap_lock before copying mm_struct David Hildenbrand (Arm)
2026-10-30 0:34 ` SJ Park
2026-10-29 20:32 ` [PATCH v2 03/47] mm/memfd: check for real shmem inodes before accessing shmem state David Hildenbrand (Arm)
2026-10-30 11:33 ` Pratyush Yadav
2026-10-30 12:06 ` David Hildenbrand (Arm)
2026-10-30 12:29 ` Pratyush Yadav
2026-10-29 20:32 ` [PATCH v2 04/47] mm/memfd: make f_pos accesses atomic David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 05/47] mm/truncate: look again if a folio left the mapping David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 06/47] mm/filemap: read mapping->a_ops->free_folio under i_lock David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 07/47] mm/filemap: don't lose a folio lock wakeup to a signal David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 08/47] mm/filemap: finish fault cleanup before dropping the fault lock David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 09/47] mm/rmap: handle device-exclusive entries in folio_referenced_one() David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 10/47] mm/huge_memory: fix list corruption when deferred_split_scan() races with deferred_split_folio() David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 11/47] mm/huge_memory: properly handle refcounted PUD mappings on fork David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 12/47] mm/huge_memory: fix livelock on device private folio David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 13/47] mm/huge_memory: fix truncate racing with PMD zapping David Hildenbrand (Arm)
2026-10-29 22:37 ` Gregory Price (Meta)
2026-10-29 20:33 ` [PATCH v2 14/47] mm/huge_memory: fix zapping migration entries for device-private THPs David Hildenbrand (Arm)
2026-10-29 22:30 ` Gregory Price (Meta)
2026-10-30 11:10 ` David Hildenbrand (Arm) [this message]
2026-10-29 20:33 ` [PATCH v2 15/47] mm/khugepaged: always recheck the pmd in try_collapse_pte_mapped_thp() David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 16/47] mm/khugepaged: fix PMD table lock leak " David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 17/47] mm/khugepaged: preserve dirty bits when collapsing PTE-mapped THPs David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 18/47] mm/khugepaged: check if PTE table is empty in try_collapse_pte_mapped_thp() David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 19/47] mm/gup: recheck the PUD under PTL in follow_pud_mask() David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 20/47] mm/gup: fix clearing folios in memfd_pin_folios() David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 21/47] mm/gup: fix out-of-bounds write for nr_pages == 0 in GUP-fast David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 22/47] mm/gup: check for overflow when converting nr_pages to bytes " David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 23/47] mm/userfaultfd: write-lock the VMA before waking waiters when unregistering David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 24/47] mm/userfaultfd: wake all waiters on unregister David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 25/47] mm/userfaultfd: wake waiters when registration modes are removed David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 26/47] mm/userfaultfd: compare exact registration modes before skipping David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 27/47] mm/mmu_gather: fix flushing ranges with 4 GiB or larger David Hildenbrand (Arm)
2026-10-30 0:57 ` SJ Park
2026-10-30 11:15 ` David Hildenbrand (Arm)
2026-10-30 11:19 ` David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 28/47] mm/mmu_notifier: finish non-blocking interval invalidation on error David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 29/47] mm/mmu_notifier: set ->mm only after mmgrab() David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 30/47] mm/mremap: use pudp_huge_get_and_clear() when moving huge PUDs David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 31/47] mm/mremap: recheck PUDs under the page table lock David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 32/47] mm/mremap: fix moving PUD leaves David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 33/47] mm/memory_hotplug: avoid races in pfn_to_online_page() with dying pgmap David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 34/47] mm/madvise: fix data loss from MADV_FREE on a KSM page David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 35/47] mm/memory: reject remote COW faults on PFN mappings David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 36/47] mm: fix unmap_mapping_range() beyond 4 GiB on 32-bit David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 37/47] mm: fix unkillable fault loop on MAP_DROPPABLE memory David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 38/47] mm: fix deadlock of mremap() against UFFDIO_MOVE David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 39/47] mm/ksm: reset the unstable trees of all nodes David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 40/47] mm/ksm: fix use of a freed anon_vma at swap-in David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 41/47] mm/ksm: check large swap-cache folios before mapping them David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 42/47] mm/vma: call ->may_split() before a partial merge David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 43/47] mm/huge_memory: split huge PUDs when adjusting VMA boundaries David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 44/47] mm/vma: don't leak the charge for stack growth David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 45/47] mm/cma: don't release CMA pages still in use David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 46/47] mm/memory-tiers: unregister empty tiers outside memory_tier_lock David Hildenbrand (Arm)
2026-10-29 20:33 ` [PATCH v2 47/47] fs/proc/task_mmu: refuse addresses beyond 32 bits on 32bit David Hildenbrand (Arm)
2026-10-30 11:19 ` [PATCH v2 00/47] mm: various (urgent?) fixes Muhammad Usama Anjum
2026-10-30 11:35 ` David Hildenbrand (Arm)
2026-10-30 12:12 ` Muhammad Usama Anjum
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