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[91.12.96.245]) by smtp.gmail.com with ESMTPSA id g197sm13579107wme.43.2021.04.30.00.49.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 30 Apr 2021 00:49:09 -0700 (PDT) To: Miaohe Lin , akpm@linux-foundation.org Cc: ziy@nvidia.com, william.kucharski@oracle.com, willy@infradead.org, yang.shi@linux.alibaba.com, aneesh.kumar@linux.ibm.com, rcampbell@nvidia.com, songliubraving@fb.com, kirill.shutemov@linux.intel.com, riel@surriel.com, hannes@cmpxchg.org, minchan@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20210429132648.305447-1-linmiaohe@huawei.com> <20210429132648.305447-4-linmiaohe@huawei.com> <68c8c4a8-c4f8-83db-7326-dabeea74239c@redhat.com> <9b511ad9-0ba1-e896-4eb5-0e91ca4b97ab@huawei.com> From: David Hildenbrand Organization: Red Hat Subject: Re: [PATCH v2 3/5] mm/huge_memory.c: add missing read-only THP checking in transparent_hugepage_enabled() Message-ID: <9c340151-6dbb-504c-e205-3edda6a5aff8@redhat.com> Date: Fri, 30 Apr 2021 09:49:08 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <9b511ad9-0ba1-e896-4eb5-0e91ca4b97ab@huawei.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Stat-Signature: ogomzjadsjqfm51qeew3sz66ysck48px X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 6BAE980192F1 Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=a2kWbMri; spf=none (imf08.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 216.205.24.124) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf08; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=216.205.24.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1619768931-12654 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 30.04.21 03:57, Miaohe Lin wrote: > On 2021/4/29 22:57, David Hildenbrand wrote: >> On 29.04.21 15:26, Miaohe Lin wrote: >>> Since commit 99cb0dbd47a1 ("mm,thp: add read-only THP support for >>> (non-shmem) FS"), read-only THP file mapping is supported. But it >>> forgot to add checking for it in transparent_hugepage_enabled(). >>> To fix it, we add checking for read-only THP file mapping and also >>> introduce helper transhuge_vma_enabled() to check whether thp is >>> enabled for specified vma to reduce duplicated code. >>> >>> Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shme= m) FS") >>> Signed-off-by: Miaohe Lin >>> --- >>> =C2=A0 include/linux/huge_mm.h | 21 +++++++++++++++++---- >>> =C2=A0 mm/huge_memory.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 |=C2= =A0 6 ++++++ >>> =C2=A0 mm/khugepaged.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= |=C2=A0 4 +--- >>> =C2=A0 mm/shmem.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0 |=C2=A0 3 +-- >>> =C2=A0 4 files changed, 25 insertions(+), 9 deletions(-) >>> >>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h >>> index 0a526f211fec..f460b74619fc 100644 >>> --- a/include/linux/huge_mm.h >>> +++ b/include/linux/huge_mm.h >>> @@ -115,6 +115,16 @@ extern struct kobj_attribute shmem_enabled_attr; >>> =C2=A0 =C2=A0 extern unsigned long transparent_hugepage_flags; >>> =C2=A0 +static inline bool transhuge_vma_enabled(struct vm_area_stru= ct *vma, >>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 unsigned long v= m_flags) >> >> You're passing the vma already, why do you pass vma->vm_flags separate= ly? It's sufficient to pass in the vma only. >> >=20 > Many thanks for comment! IMO, vm_flags may not always equal to vma->vm_= flags. When hugepage_vma_check() > is called from collapse_pte_mapped_thp, vma_flags =3D vma->vm_flags | V= M_HUGEPAGE. So I think we should > pass vm_flags here. Oh, sorry, I missed the hugepage_vma_check() user. That's unfortunate. >>> =C2=A0 static inline void prep_transhuge_page(struct page *page) {} >>> =C2=A0 =C2=A0 static inline bool is_transparent_hugepage(struct page= *page) >>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>> index 76ca1eb2a223..e24a96de2e37 100644 >>> --- a/mm/huge_memory.c >>> +++ b/mm/huge_memory.c >>> @@ -68,12 +68,18 @@ bool transparent_hugepage_enabled(struct vm_area_= struct *vma) >>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 /* The addr is used to check if the v= ma size fits */ >>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 unsigned long addr =3D (vma->vm_end &= HPAGE_PMD_MASK) - HPAGE_PMD_SIZE; >>> =C2=A0 +=C2=A0=C2=A0=C2=A0 if (!transhuge_vma_enabled(vma, vma->vm_f= lags)) >>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return false; >>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (!transhuge_vma_suitable(vma, addr= )) >>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return false; >>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (vma_is_anonymous(vma)) >>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return __tran= sparent_hugepage_enabled(vma); >>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (vma_is_shmem(vma)) >>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return shmem_= huge_enabled(vma); >>> +=C2=A0=C2=A0=C2=A0 if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && vm= a->vm_file && >>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 !inode_is_open_for_write(= vma->vm_file->f_inode) && >>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 (vma->vm_flags & VM_EXEC)= ) >>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return true; >> >> Nit: I'm really wondering why we have 3 different functions that sound= like they are doing the same thing >> >> transparent_hugepage_enabled(vma) >> transhuge_vma_enabled() >> transhuge_vma_suitable() >> >> Which check belongs where? Does it really have to be that complicated? >> >=20 > IMO, transhuge_vma_suitable() checks whether pgoff , vm_start and vm_en= d is possible for thp. > transhuge_vma_enabled() checks whether thp is explicitly disabled throu= gh madvise. > And transparent_hugepage_enabled() use these helpers to get the conclus= ion whether thp is > enabled for specified vma. >=20 > Any suggestions? transparent_hugepage_enabled() vs. transhuge_vma_enabled() is really=20 sub-optimal naming. I guess "transparent_hugepage_active()" would have=20 been clearer (enabled + suitable + applicable). Cannot really give a=20 good suggestion here on how to name transhuge_vma_enabled() differently. We now have transparent_hugepage_enabled() -> transhuge_vma_enabled() -> __transparent_hugepage_enabled() -> transhuge_vma_enabled() -> shmem_huge_enabled() -> transhuge_vma_enabled() That looks sub-optimal as well. Maybe we should have a static inline bool file_thp_enabled(struct vma *vma) { return transhuge_vma_enabled() && IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !inode_is_open_for_write(vma->vm_file->f_inode) && (vma->vm_flags & VM_EXEC)) } and in transparent_hugepage_enabled() only do a if (vma->vm_file) return file_thp_enabled(vma); Or move the transhuge_vma_enabled() check completely to=20 transparent_hugepage_enabled() if possible. --=20 Thanks, David / dhildenb