From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E7411C77B73 for ; Mon, 1 May 2023 17:50:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230429AbjEARum (ORCPT ); Mon, 1 May 2023 13:50:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40390 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232518AbjEARuf (ORCPT ); Mon, 1 May 2023 13:50:35 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 62FFC10CC for ; Mon, 1 May 2023 10:50:33 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id 3f1490d57ef6-b9a77926afbso5456333276.3 for ; Mon, 01 May 2023 10:50:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1682963432; x=1685555432; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=Vw7vchvPa5zb0i4uc6VlbyjDM+/1CtZDGIGJ1EuR9xw=; b=5HsHeOLjpvUCguo8Lk5686FqyMyO/K1KiWJihXWf5ybeHIs84XPoHkts2mjy/kUs1l OVyccOydInIzF83t7slw6eryjNnVfxRNEDu94e6rnWhRVLxxc+mL+BA49regOAf5kslZ LLCq5lh1PW8I8Z10gv2qYm/fP8iSSz6PfSup+xBmEYK32jLAyJ72rp0lAb9Ja6S+ZNFp vpHyDid2/Jb8uaq1IaiD5weLPcePb/KM0hw6ZU+KPOncjNStmsgmO9gjEswNlynFjsvG Mb2tpXrasG6CZ2vTifbGdq0/Y2mX7Cc6JG0UUlhWyX6kwnaEJR4lOKi95Lq/0G+NMlK8 jz4Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1682963432; x=1685555432; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Vw7vchvPa5zb0i4uc6VlbyjDM+/1CtZDGIGJ1EuR9xw=; b=fPlaVjcQAVYtR3stwK2gCemgoglSB9UVCRIL/TLHWavSyZ5MiCPUw8+bgwkORdJkx0 UqQo04bogOlySy8Q5qPOYSZ1jtNEfFzUkqzJtvG84axi3ak6/l1dqz8FLxbB2uSEhmKZ 96hGpIKdRlY/zpxoZbuPKzGOzkDHruesx+61nW16D8bEuR2c2I35V4sDL7ym7/jhH0kJ +SU5tEcI4VBkuKyaaTWDp0gpQ0jayanxx7RAYYhz38TlHC2oypTYZ71jPzFcS/Cy+PWU tHcs63oWdvBV3Vu+BQIkSTUhSqpjub4/OfyInb3oh4xVB9R/LC49DDNvGx9vTTqCn/NP Asww== X-Gm-Message-State: AC+VfDxK6Ei2FO0vMGSb32wk70svfkx7H3PJQ7tHacgaV4Qh2HsneuFv YYGCEuPeMfO14pr5YddduFl1IVX71/M= X-Google-Smtp-Source: ACHHUZ52U0jmkTB2neK+iG10+QPSsqzCMma8yYtYnx1BEqBYvpEc0F6TFjBKuNu+xchIpilXB3tZ+Ex1C4w= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:201:6d24:3efd:facc:7ac4]) (user=surenb job=sendgmr) by 2002:a25:4884:0:b0:b9a:6a68:7c25 with SMTP id v126-20020a254884000000b00b9a6a687c25mr8582160yba.5.1682963432608; Mon, 01 May 2023 10:50:32 -0700 (PDT) Date: Mon, 1 May 2023 10:50:24 -0700 In-Reply-To: <20230501175025.36233-1-surenb@google.com> Mime-Version: 1.0 References: <20230501175025.36233-1-surenb@google.com> X-Mailer: git-send-email 2.40.1.495.gc816e09b53d-goog Message-ID: <20230501175025.36233-2-surenb@google.com> Subject: [PATCH 2/3] mm: drop VMA lock before waiting for migration From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: willy@infradead.org, hannes@cmpxchg.org, mhocko@suse.com, josef@toxicpanda.com, jack@suse.cz, ldufour@linux.ibm.com, laurent.dufour@fr.ibm.com, michel@lespinasse.org, liam.howlett@oracle.com, jglisse@google.com, vbabka@suse.cz, minchan@google.com, dave@stgolabs.net, punit.agrawal@bytedance.com, lstoakes@gmail.com, hdanton@sina.com, apopple@nvidia.com, surenb@google.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org migration_entry_wait does not need VMA lock, therefore it can be dropped before waiting. Introduce VM_FAULT_VMA_UNLOCKED to indicate that VMA lock was dropped while in handle_mm_fault(). Note that once VMA lock is dropped, the VMA reference can't be used as there are no guarantees it was not freed. Signed-off-by: Suren Baghdasaryan --- arch/arm64/mm/fault.c | 3 ++- arch/powerpc/mm/fault.c | 3 ++- arch/s390/mm/fault.c | 3 ++- arch/x86/mm/fault.c | 3 ++- include/linux/mm_types.h | 6 +++++- mm/memory.c | 12 ++++++++++-- 6 files changed, 23 insertions(+), 7 deletions(-) diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 9e0db5c387e3..8fa281f49d61 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -602,7 +602,8 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr, } fault = handle_mm_fault(vma, addr & PAGE_MASK, mm_flags | FAULT_FLAG_VMA_LOCK, regs); - vma_end_read(vma); + if (!(fault & VM_FAULT_VMA_UNLOCKED)) + vma_end_read(vma); if (!(fault & VM_FAULT_RETRY)) { count_vm_vma_lock_event(VMA_LOCK_SUCCESS); diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index 531177a4ee08..b27730f07141 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c @@ -494,7 +494,8 @@ static int ___do_page_fault(struct pt_regs *regs, unsigned long address, } fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs); - vma_end_read(vma); + if (!(fault & VM_FAULT_VMA_UNLOCKED)) + vma_end_read(vma); if (!(fault & VM_FAULT_RETRY)) { count_vm_vma_lock_event(VMA_LOCK_SUCCESS); diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c index b65144c392b0..cc923dbb0821 100644 --- a/arch/s390/mm/fault.c +++ b/arch/s390/mm/fault.c @@ -418,7 +418,8 @@ static inline vm_fault_t do_exception(struct pt_regs *regs, int access) goto lock_mmap; } fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs); - vma_end_read(vma); + if (!(fault & VM_FAULT_VMA_UNLOCKED)) + vma_end_read(vma); if (!(fault & VM_FAULT_RETRY)) { count_vm_vma_lock_event(VMA_LOCK_SUCCESS); goto out; diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index e4399983c50c..ef62ab2fd211 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1347,7 +1347,8 @@ void do_user_addr_fault(struct pt_regs *regs, goto lock_mmap; } fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs); - vma_end_read(vma); + if (!(fault & VM_FAULT_VMA_UNLOCKED)) + vma_end_read(vma); if (!(fault & VM_FAULT_RETRY)) { count_vm_vma_lock_event(VMA_LOCK_SUCCESS); diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 306a3d1a0fa6..b3b57c6da0e1 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -1030,6 +1030,7 @@ typedef __bitwise unsigned int vm_fault_t; * fsync() to complete (for synchronous page faults * in DAX) * @VM_FAULT_COMPLETED: ->fault completed, meanwhile mmap lock released + * @VM_FAULT_VMA_UNLOCKED: VMA lock was released * @VM_FAULT_HINDEX_MASK: mask HINDEX value * */ @@ -1047,6 +1048,7 @@ enum vm_fault_reason { VM_FAULT_DONE_COW = (__force vm_fault_t)0x001000, VM_FAULT_NEEDDSYNC = (__force vm_fault_t)0x002000, VM_FAULT_COMPLETED = (__force vm_fault_t)0x004000, + VM_FAULT_VMA_UNLOCKED = (__force vm_fault_t)0x008000, VM_FAULT_HINDEX_MASK = (__force vm_fault_t)0x0f0000, }; @@ -1070,7 +1072,9 @@ enum vm_fault_reason { { VM_FAULT_RETRY, "RETRY" }, \ { VM_FAULT_FALLBACK, "FALLBACK" }, \ { VM_FAULT_DONE_COW, "DONE_COW" }, \ - { VM_FAULT_NEEDDSYNC, "NEEDDSYNC" } + { VM_FAULT_NEEDDSYNC, "NEEDDSYNC" }, \ + { VM_FAULT_COMPLETED, "COMPLETED" }, \ + { VM_FAULT_VMA_UNLOCKED, "VMA_UNLOCKED" } struct vm_special_mapping { const char *name; /* The name, e.g. "[vdso]". */ diff --git a/mm/memory.c b/mm/memory.c index 41f45819a923..8222acf74fd3 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3714,8 +3714,16 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) entry = pte_to_swp_entry(vmf->orig_pte); if (unlikely(non_swap_entry(entry))) { if (is_migration_entry(entry)) { - migration_entry_wait(vma->vm_mm, vmf->pmd, - vmf->address); + /* Save mm in case VMA lock is dropped */ + struct mm_struct *mm = vma->vm_mm; + + if (vmf->flags & FAULT_FLAG_VMA_LOCK) { + /* No need to hold VMA lock for migration */ + vma_end_read(vma); + /* CAUTION! VMA can't be used after this */ + ret |= VM_FAULT_VMA_UNLOCKED; + } + migration_entry_wait(mm, vmf->pmd, vmf->address); } else if (is_device_exclusive_entry(entry)) { vmf->page = pfn_swap_entry_to_page(entry); ret = remove_device_exclusive_entry(vmf); -- 2.40.1.495.gc816e09b53d-goog