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Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Pedro Falcato , Zi Yan References: <20260916043153.2631696-1-wangkefeng.wang@huawei.com> <9da6298e-485a-41af-a42f-7dd05c571125@kernel.org> Content-Language: en-US From: Kefeng Wang In-Reply-To: <9da6298e-485a-41af-a42f-7dd05c571125@kernel.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: kwepems100002.china.huawei.com (7.221.188.206) To kwepemk300003.china.huawei.com (7.202.195.93) X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 51A83C0003 X-Stat-Signature: oi78zqmfqiyffx9ue7p1hmxuy98xt3fc X-HE-Tag: 1789541432-554457 X-HE-Meta: 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 wc5lCnpK quqIxo8cXmPIJ2KljaQv2JVDiLBuwE1iO0Nih6u2YkMrxYq8QnrO5FusW4DLLFlfhJ+5pWA0dmP1G5pr+ESrbI1uo324V0Ok7+FN8YdkZyN7BCcrnmxmpPUr0MaMsj7uFlcSXdu6HZCgMRIiaJ9JMOFvRr9JUsxKao8MGD0kNHaDwtKZn3ITrA9TqkgoXC/24ELD4semTZOTTNtAjcPP9uQf+VQTclddavo7WAQyRgsFvUoi2LcgZHM1bjtbRue95Z1UoJ5nGxViR3SuYiA5MdHldnyDpkJ1GVvAaYkpO58WZ21awP2jKCELKGEPoZVKy4THxv5TU5MbZsJnC/K7CllDMyy6pMMZ8MBUsaUWriTkCFGs= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/16/2026 2:33 PM, David Hildenbrand (Arm) wrote: > On 9/16/26 06:31, Kefeng Wang wrote: >> do_mincore() performs a read-only, per-VMA residency query, >> making it a good candidate for per-VMA locking. Convert it >> to acquire the per-VMA lock, thereby reducing contention on >> the per-MM mmap_lock. >> >> Reviewed-by: Pedro Falcato >> Signed-off-by: Kefeng Wang >> --- >> v3: >> - add vma_assert_locked, update changelog/comment, per David > > It likely was Lorenzo :) > Oh, I'm completely blind :) >> - Add RB >> v2, (RESEND): >> - using new vma_start_read_unlocked() API, suggestted by Pedro Falcato >> v1: >> - https://lore.kernel.org/linux-mm/20260701144047.3786939-2-wangkefeng.wang@huawei.com/ >> >> mm/mincore.c | 29 +++++++++++++++++------------ >> 1 file changed, 17 insertions(+), 12 deletions(-) >> >> diff --git a/mm/mincore.c b/mm/mincore.c >> index c086836bc4bc..0fe50f8a7e62 100644 >> --- a/mm/mincore.c >> +++ b/mm/mincore.c >> @@ -235,24 +235,22 @@ static const struct mm_walk_ops mincore_walk_ops = { >> .pmd_entry = mincore_pte_range, >> .pte_hole = mincore_unmapped_range, >> .hugetlb_entry = mincore_hugetlb, >> - .walk_lock = PGWALK_RDLOCK, >> + .walk_lock = PGWALK_VMA_RDLOCK_VERIFY, >> }; >> >> /* >> * Do a chunk of "sys_mincore()". We've already checked >> - * all the arguments, we hold the mmap semaphore: we should >> + * all the arguments, we hold the VMA read lock: we should >> * just return the amount of info we're asked for. >> */ >> -static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec) >> +static long do_mincore(struct vm_area_struct *vma, unsigned long addr, >> + unsigned long pages, unsigned char *vec) >> { >> - struct vm_area_struct *vma; >> - unsigned long end; >> + unsigned long end = min(vma->vm_end, addr + (pages << PAGE_SHIFT)); >> int err; >> >> - vma = vma_lookup(current->mm, addr); >> - if (!vma) >> - return -ENOMEM; >> - end = min(vma->vm_end, addr + (pages << PAGE_SHIFT)); >> + vma_assert_locked(vma); > > I think Lorenzo asked whether we should do that. But the walk_page_vma() further > below would already verify that due to PGWALK_VMA_RDLOCK_VERIFY (see > process_vma_walk_lock) so not sure if that's really required here. I misunderstood Lorenzo's intention, which has already been verified through the PGWALK_VMA_RDLOCK_VERIFY check. I don't think it has much value, but adding it doesn't do any harm. > > AFAIKS, everything we do in mincore_pte_range() should be compatible with the > VMA lock, including the swap and pagecache handling. > > Acked-by: David Hildenbrand (Arm) >