From patchwork Thu Jan 25 00:13:28 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Suren Baghdasaryan X-Patchwork-Id: 767871 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6F2B0385 for ; Thu, 25 Jan 2024 00:13:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706141614; cv=none; b=suWdfcvpXBpGDQgX6Xgp2F/Vd5TNnZz9ITHFEgjm/cocyml/zCQ/qFeuhT1b8+FlNHFhmBL8RPWxnxPIWxGNMKtuPLaSFc2X2mMqYoN/nNDZ0jJJtv0bAnqY5bFupsj7woRhs1v2T+laJXwApZIzGPXbSZ96xRlpnT8yo1WTdRc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706141614; c=relaxed/simple; bh=KeDhP+xDEL1TMTboAgFtXRykmAfuqzqg9CJvAJXtD5M=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=VmUjQ2j3Wg/wMzGzsWCUXSr46Qi3SC+AAmU4PMygRRdLlGo2skTLpanJZFpypa8j6tbiOAWj9MYZbEgt+DkJI/Dtb9FmN10+C/mSMjKmX63dkLyr9F4LveYwoorLe5Tqq9op7BCJ9TuHl7fThO0ITPmYaT6MFHMlhhBMIa3sWZs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--surenb.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=1X57XxK8; arc=none smtp.client-ip=209.85.128.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--surenb.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="1X57XxK8" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-5efb07ddb0fso74864957b3.0 for ; Wed, 24 Jan 2024 16:13:32 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1706141611; x=1706746411; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=cPu242y3p9rQer5EHrWEZnnEQJcAmzowYqkBYJsGGGI=; b=1X57XxK8kLFWMnqQXT6ef9m2hHNn7cN6e+KeVbLZWzIISpl3Ek3GGLhwdfFRDw/ERt 3DAioZgxt+5BHyTHfiDwjWw3HSEDOKEJI5U3T6a4OXxd8F9815A0HjoDu8D8O3IenjGX Oq95SWP6H9U3ty3UZlQV+IQuhktvwcs1biEqy3Mzu/UCBoBa13LIC6YI3ZtvL+J3akYT Cv/vTycBYBWZUX55TReHkVE6sesA5gl9sTHuIOxLZUK4micWLleazlVbdEPx/qoxQo6z 9nNj0eh4epS0Bpj7c7l73GwlNeD4S1vNsRYGOXr6rGrh5RVx0xRh96+00opq0QetCEjg cBMQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1706141611; x=1706746411; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=cPu242y3p9rQer5EHrWEZnnEQJcAmzowYqkBYJsGGGI=; b=TAn+0S2MVm/YQ2BkhFEqKwjaj6cfN1uhGZlFY7vveYgHlZiiOPZOjdQWAUAKqgfOt3 j4sU2+Jb5pKUuT+38dQNPLNY9L99EXR2xYQuUngVXv7V9lLI/tvDc3TweLAKW4Dq0PQ6 +8pdYv6ezI1ulDAHWIn36cZeOcBHbv5q+COf/jEz98dRIdQ+DcNMLLKrhnFXUMbadSic G1U3vvfnSs+6Uh7cwf8Z+s6f7KDnkvmz5VKa7uoU/HVQHlJjhOqTGScpIasbL4nYz+Aa RRZil7VGibyHaJu6Lw5KXnrGffI76ACQkbNA93LxrG9j8bB7v+sLFCwMPUIOAYC41kCT YIFA== X-Gm-Message-State: AOJu0Yw1X9n53xn9Th6u8zA3Bh7jU2t85wvQ7FylWiVuyk8ie826xOeP lpVvkuPmm89gmzwmRJc8BXmE8DodZ+zrTUaNw1rn6QsH+M1WIp/9jjRUc0hf93Z3C74002oJyAb wiw== X-Google-Smtp-Source: AGHT+IEZLtB9otomnw6MNDdoYLF/2uX4yU3la82s4yNMlhvEgVEVg/VGQzuPnFpome6BU13TgA+OWJtInTs= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:201:ff85:6a8d:d789:76fa]) (user=surenb job=sendgmr) by 2002:a0d:eb89:0:b0:5ff:ea65:3a71 with SMTP id u131-20020a0deb89000000b005ffea653a71mr549405ywe.3.1706141611543; Wed, 24 Jan 2024 16:13:31 -0800 (PST) Date: Wed, 24 Jan 2024 16:13:28 -0800 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.43.0.429.g432eaa2c6b-goog Message-ID: <20240125001328.335127-1-surenb@google.com> Subject: [PATCH 1/2] userfaultfd: handle zeropage moves by UFFDIO_MOVE From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: viro@zeniv.linux.org.uk, brauner@kernel.org, shuah@kernel.org, aarcange@redhat.com, lokeshgidra@google.com, peterx@redhat.com, david@redhat.com, ryan.roberts@arm.com, hughd@google.com, mhocko@suse.com, axelrasmussen@google.com, rppt@kernel.org, willy@infradead.org, Liam.Howlett@oracle.com, jannh@google.com, zhangpeng362@huawei.com, bgeffon@google.com, kaleshsingh@google.com, ngeoffray@google.com, jdduke@google.com, surenb@google.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, kernel-team@android.com Current implementation of UFFDIO_MOVE fails to move zeropages and returns EBUSY when it encounters one. We can handle them by mapping a zeropage at the destination and clearing the mapping at the source. This is done both for ordinary and for huge zeropages. Signed-off-by: Suren Baghdasaryan --- Applies cleanly over mm-unstable branch. mm/huge_memory.c | 105 +++++++++++++++++++++++++++-------------------- mm/userfaultfd.c | 42 +++++++++++++++---- 2 files changed, 96 insertions(+), 51 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index f40feb31b507..5dcc02c25e97 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2190,13 +2190,18 @@ int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pm } src_page = pmd_page(src_pmdval); - if (unlikely(!PageAnonExclusive(src_page))) { - spin_unlock(src_ptl); - return -EBUSY; - } - src_folio = page_folio(src_page); - folio_get(src_folio); + if (!is_huge_zero_pmd(src_pmdval)) { + if (unlikely(!PageAnonExclusive(src_page))) { + spin_unlock(src_ptl); + return -EBUSY; + } + + src_folio = page_folio(src_page); + folio_get(src_folio); + } else + src_folio = NULL; + spin_unlock(src_ptl); flush_cache_range(src_vma, src_addr, src_addr + HPAGE_PMD_SIZE); @@ -2204,19 +2209,22 @@ int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pm src_addr + HPAGE_PMD_SIZE); mmu_notifier_invalidate_range_start(&range); - folio_lock(src_folio); + if (src_folio) { + folio_lock(src_folio); - /* - * split_huge_page walks the anon_vma chain without the page - * lock. Serialize against it with the anon_vma lock, the page - * lock is not enough. - */ - src_anon_vma = folio_get_anon_vma(src_folio); - if (!src_anon_vma) { - err = -EAGAIN; - goto unlock_folio; - } - anon_vma_lock_write(src_anon_vma); + /* + * split_huge_page walks the anon_vma chain without the page + * lock. Serialize against it with the anon_vma lock, the page + * lock is not enough. + */ + src_anon_vma = folio_get_anon_vma(src_folio); + if (!src_anon_vma) { + err = -EAGAIN; + goto unlock_folio; + } + anon_vma_lock_write(src_anon_vma); + } else + src_anon_vma = NULL; dst_ptl = pmd_lockptr(mm, dst_pmd); double_pt_lock(src_ptl, dst_ptl); @@ -2225,45 +2233,54 @@ int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pm err = -EAGAIN; goto unlock_ptls; } - if (folio_maybe_dma_pinned(src_folio) || - !PageAnonExclusive(&src_folio->page)) { - err = -EBUSY; - goto unlock_ptls; - } + if (src_folio) { + if (folio_maybe_dma_pinned(src_folio) || + !PageAnonExclusive(&src_folio->page)) { + err = -EBUSY; + goto unlock_ptls; + } - if (WARN_ON_ONCE(!folio_test_head(src_folio)) || - WARN_ON_ONCE(!folio_test_anon(src_folio))) { - err = -EBUSY; - goto unlock_ptls; - } + if (WARN_ON_ONCE(!folio_test_head(src_folio)) || + WARN_ON_ONCE(!folio_test_anon(src_folio))) { + err = -EBUSY; + goto unlock_ptls; + } - folio_move_anon_rmap(src_folio, dst_vma); - WRITE_ONCE(src_folio->index, linear_page_index(dst_vma, dst_addr)); + folio_move_anon_rmap(src_folio, dst_vma); + WRITE_ONCE(src_folio->index, linear_page_index(dst_vma, dst_addr)); - src_pmdval = pmdp_huge_clear_flush(src_vma, src_addr, src_pmd); - /* Folio got pinned from under us. Put it back and fail the move. */ - if (folio_maybe_dma_pinned(src_folio)) { - set_pmd_at(mm, src_addr, src_pmd, src_pmdval); - err = -EBUSY; - goto unlock_ptls; - } + src_pmdval = pmdp_huge_clear_flush(src_vma, src_addr, src_pmd); + /* Folio got pinned from under us. Put it back and fail the move. */ + if (folio_maybe_dma_pinned(src_folio)) { + set_pmd_at(mm, src_addr, src_pmd, src_pmdval); + err = -EBUSY; + goto unlock_ptls; + } - _dst_pmd = mk_huge_pmd(&src_folio->page, dst_vma->vm_page_prot); - /* Follow mremap() behavior and treat the entry dirty after the move */ - _dst_pmd = pmd_mkwrite(pmd_mkdirty(_dst_pmd), dst_vma); + _dst_pmd = mk_huge_pmd(&src_folio->page, dst_vma->vm_page_prot); + /* Follow mremap() behavior and treat the entry dirty after the move */ + _dst_pmd = pmd_mkwrite(pmd_mkdirty(_dst_pmd), dst_vma); + } else { + src_pmdval = pmdp_huge_clear_flush(src_vma, src_addr, src_pmd); + _dst_pmd = mk_huge_pmd(src_page, dst_vma->vm_page_prot); + } set_pmd_at(mm, dst_addr, dst_pmd, _dst_pmd); src_pgtable = pgtable_trans_huge_withdraw(mm, src_pmd); pgtable_trans_huge_deposit(mm, dst_pmd, src_pgtable); unlock_ptls: double_pt_unlock(src_ptl, dst_ptl); - anon_vma_unlock_write(src_anon_vma); - put_anon_vma(src_anon_vma); + if (src_anon_vma) { + anon_vma_unlock_write(src_anon_vma); + put_anon_vma(src_anon_vma); + } unlock_folio: /* unblock rmap walks */ - folio_unlock(src_folio); + if (src_folio) + folio_unlock(src_folio); mmu_notifier_invalidate_range_end(&range); - folio_put(src_folio); + if (src_folio) + folio_put(src_folio); return err; } #endif /* CONFIG_USERFAULTFD */ diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 3548b3e31a97..5fbf4da15c5c 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -959,6 +959,31 @@ static int move_swap_pte(struct mm_struct *mm, return 0; } +static int move_zeropage_pte(struct mm_struct *mm, + struct vm_area_struct *dst_vma, + struct vm_area_struct *src_vma, + unsigned long dst_addr, unsigned long src_addr, + pte_t *dst_pte, pte_t *src_pte, + pte_t orig_dst_pte, pte_t orig_src_pte, + spinlock_t *dst_ptl, spinlock_t *src_ptl) +{ + pte_t zero_pte; + + double_pt_lock(dst_ptl, src_ptl); + if (!pte_same(ptep_get(src_pte), orig_src_pte) || + !pte_same(ptep_get(dst_pte), orig_dst_pte)) + return -EAGAIN; + + zero_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr), + dst_vma->vm_page_prot)); + ptep_clear_flush(src_vma, src_addr, src_pte); + set_pte_at(mm, dst_addr, dst_pte, zero_pte); + double_pt_unlock(dst_ptl, src_ptl); + + return 0; +} + + /* * The mmap_lock for reading is held by the caller. Just move the page * from src_pmd to dst_pmd if possible, and return true if succeeded @@ -1041,6 +1066,14 @@ static int move_pages_pte(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, } if (pte_present(orig_src_pte)) { + if (is_zero_pfn(pte_pfn(orig_src_pte))) { + err = move_zeropage_pte(mm, dst_vma, src_vma, + dst_addr, src_addr, dst_pte, src_pte, + orig_dst_pte, orig_src_pte, + dst_ptl, src_ptl); + goto out; + } + /* * Pin and lock both source folio and anon_vma. Since we are in * RCU read section, we can't block, so on contention have to @@ -1404,19 +1437,14 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm, err = -ENOENT; break; } - /* Avoid moving zeropages for now */ - if (is_huge_zero_pmd(*src_pmd)) { - spin_unlock(ptl); - err = -EBUSY; - break; - } /* Check if we can move the pmd without splitting it. */ if (move_splits_huge_pmd(dst_addr, src_addr, src_start + len) || !pmd_none(dst_pmdval)) { struct folio *folio = pfn_folio(pmd_pfn(*src_pmd)); - if (!folio || !PageAnonExclusive(&folio->page)) { + if (!folio || (!is_huge_zero_page(&folio->page) && + !PageAnonExclusive(&folio->page))) { spin_unlock(ptl); err = -EBUSY; break;