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Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Pedro Falcato , David Hildenbrand , Zi Yan , Kefeng Wang Subject: [PATCH mm-new v3] mm: mincore: use per-vma lock during page table walk Date: Wed, 16 Sep 2026 12:31:52 +0800 Message-ID: <20260916043153.2631696-1-wangkefeng.wang@huawei.com> X-Mailer: git-send-email 2.55.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.50.87.83] X-ClientProxiedBy: kwepems100002.china.huawei.com (7.221.188.206) To kwepemk300003.china.huawei.com (7.202.195.93) X-Rspam-User: X-Rspamd-Queue-Id: AC49F1A0002 X-Stat-Signature: yqzupkpxi4opwhrex4opkwparhnztwsu X-Rspamd-Server: rspam01 X-HE-Tag: 1789533125-167316 X-HE-Meta: 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 IWuHeK5q OwZJu3OaVJfH00jSdMmkEOEYb/JwJdpWzXWxe61nCGbi9hD9psfmLF/8ovjEgNe+OYx9Y860AVbFHV9XDUGhOO+Hk2w63I12UK+xK5jtBSobEpYrmtbgz48yAWrMbVt0SfXJLpYx2U8jzNDRpFg/tP9VBCRZmfs9qxAMlA2wV0eSEVOMuE/8sr91LAWfdBQreXuaUFGoRuxr3C/Mzn9gf2VqsF+HUn7uvK5TTOEM/P+SOtglx2M6londUaOGujFrQ5m/CBAgogXYJL0WlynjH2qpw9Cv9ikobd82vlNNbOmHPTYgWSmSMa2ZD8robYn4cfpfy Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 - 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); + if (!can_do_mincore(vma)) { unsigned long pages = DIV_ROUND_UP(end - addr, PAGE_SIZE); memset(vec, 1, pages); @@ -319,13 +317,20 @@ SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, retval = 0; while (pages) { + struct vm_area_struct *vma; + + vma = vma_start_read_unlocked(current->mm, start); + if (!vma) { + retval = -ENOMEM; + break; + } + /* * Do at most PAGE_SIZE entries per iteration, due to * the temporary buffer size. */ - mmap_read_lock(current->mm); - retval = do_mincore(start, min(pages, PAGE_SIZE), tmp); - mmap_read_unlock(current->mm); + retval = do_mincore(vma, start, min(pages, PAGE_SIZE), tmp); + vma_end_read(vma); if (retval <= 0) break; -- 2.55.0