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ESMTP id 4b5YCF2LQRz2SSKb; Mon, 26 May 2025 11:17:45 +0000 (GMT) Mime-Version: 1.0 Subject: reply: [RFC] pin_user_pages_fast failure count increased Reply-To: jaewon31.kim@samsung.com From: Jaewon Kim To: David Hildenbrand , Hyesoo Yu , Zhaoyang Huang CC: John Hubbard , Jaewon Kim , "zhaoyang.huang@unisoc.com" , "surenb@google.com" , "Steve.Kang@unisoc.com" , Jaewon Kim , "linux-mm@kvack.org" , Jang-Hyuck Kim X-Priority: 3 X-Content-Kind-Code: NORMAL In-Reply-To: X-Drm-Type: N,general X-Msg-Generator: Mail X-Msg-Type: PERSONAL X-Reply-Demand: N Message-ID: <20250526111744epcms1p89d664f5cebd1e690730f32b66c24e3c0@epcms1p8> Date: Mon, 26 May 2025 20:17:44 +0900 X-CMS-MailID: 20250526111744epcms1p89d664f5cebd1e690730f32b66c24e3c0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" CMS-TYPE: 101P X-CPGSPASS: Y X-CPGSPASS: Y cpgsPolicy: CPGSC10-711,Y X-CFilter-Loop: Reflected X-CMS-RootMailID: 20250522130101epcas1p435244c12cfc9bb7895008b8ea98af064 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 we+skart Uu3Ng8Ea1Gi59Kb/a+EfOExDi+XnJj8JsQQJTk15QbD1Du+qOm5m7u7md5FSkCl9ZdO6cHoJDemrZdFsFRu4nkfcB76TOUHR/FDHL7+dsb6itR0bGPZKVqUIjGFkMJ/auom5aG1k+uyxiiHm5xobwuS33ryAzwZZDhTH0QU/JpDzQhZkpqJ4/u86yKSCAz6s0FD22enQJXfXtlCkZlqnAO70vuYeJgarej02eXBtEtowXlBZu66hBMoJwf7lToIUydY9AhDfBznoVa3feCSGbZ26KMDNWuctkl7h6VN9DV4RtY7VRViChEh4wrOhZCzPI7+9w7AWkzqKrNG5MySVKAqCUyH8x4l3fzc3oCv6Sq8Gpas4XyDmapmXUYrYztJVutG/V+fiVDDZJtg/WahNFUTe9RsCxUJbKtZU19inRS+rMpDXcoAQGwjgkQ2Es1W78cQESxgdxjpc4ifLqWyO0H4k6eg== 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: List-Subscribe: List-Unsubscribe: >On 26.05.25 11:33, Hyesoo Yu wrote: >> On Mon, May 26, 2025 at 04:05:16PM +0800, Zhaoyang Huang wrote: >>> On Mon, May 26, 2025 at 3:50?PM Hyesoo Yu wro= te: >>>> >>>> On Thu, May 22, 2025 at 07:52:41PM -0700, John Hubbard wrote: >>>>> On 5/22/25 7:37 PM, =EA=B9=80=EC=9E=AC=EC=9B=90=20wrote:=0D=0A>>>>>= =20...=0D=0A>>>>>>=20I=20think=20this=20is=20what=20you=20meant,=20please= =20let=20me=20know=20if=20you=20have=20an=20idea=20to=20make=20this=20nicer= .=0D=0A>>>>>>=20We=20may=20be=20to=20able=20to=20prepare=20the=20patch=20ne= xt=20week.=0D=0A>>>>>>=0D=0A>>>>>>=20=20=20static=20long=0D=0A>>>>>>=20=20= =20check_and_migrate_movable_pages_or_folios(struct=20pages_or_folios=20*po= fs)=0D=0A>>>>>>=20=20=20=7B=0D=0A>>>>>>=20+=20=20=20=20=20=20=20bool=20any_= unpinnable;=0D=0A>>>>>>=20=20=20=20=20=20=20=20=20=20LIST_HEAD(movable_foli= o_list);=0D=0A>>>>>>=0D=0A>>>>>>=20-=20=20=20=20=20=20=20collect_longterm_u= npinnable_folios(&movable_folio_list,=20pofs);=0D=0A>>>>>>=20-=20=20=20=20= =20=20=20if=20(list_empty(&movable_folio_list))=0D=0A>>>>>>=20-=20=20=20=20= =20=20=20=20=20=20=20=20=20=20=20return=200;=0D=0A>>>>>>=20+=20=20=20=20=20= =20=20any_unpinnable=20=3D=20collect_longterm_unpinnable_folios(&movable_fo= lio_list,=20pofs);=0D=0A>>>>>>=20+=20=20=20=20=20=20=20if=20(list_empty(&mo= vable_folio_list))=20=7B=0D=0A>>>>>>=20+=20=20=20=20=20=20=20=20=20=20=20= =20=20=20=20if=20(any_unpinnable)=0D=0A>>>>>>=20+=20=20=20=20=20=20=20=20= =20=20=20=20=20=20=20=20=20=20=20=20=20=20=20pofs_unpin(pofs);=0D=0A>>>>>= =0D=0A>>>>>=20I=20think=20this=20is=20correct,=20although=20as=20I=20mentio= ned=20in=20the=20other=20thread,=0D=0A>>>>>=20that=20implies=20that=20commi= t=201aaf8c122918=20(which=20didn't=20add=20nor=20remove=0D=0A>>>>>=20any=20= pof=20unpinning)=20is=20probably=20not=20the=20true=20or=20only=20culprit,= =20right?=0D=0A>>>>>=0D=0A>>>>>>=20+=20=20=20=20=20=20=20=20=20=20=20=20=20= =20=20return=20any_unpinnable=20?=20-EAGAIN=20:=200;=0D=0A>>>>>=0D=0A>>>>>= =20Ha,=20the=20=22?=22=20operator=20almost=20always=20does=20more=20harm=20= than=20good.=0D=0A>>>>>=0D=0A>>>>>=20Here,=20for=20example,=20it=20has=20ob= scured=20from=20you=20the=20fact=20that=20any_unpinnable=0D=0A>>>>>=20is=20= being=20checked=20twice,=20when=20you=20could=20have=20merged=20those=20int= o=20a=20single=20=22if=22.=0D=0A>>>>>=0D=0A>>>>=0D=0A>>>>=20Hello,=0D=0A>>>= >=0D=0A>>>>=20I=20was=20wondering=20if=20the=20original=20problem=20-=20an= =20infinite=20loop=20when=20pages=20allocated=20by=0D=0A>>>>=20cma_alloc()= =20in=20vm_ops->fault=20are=20passed=20to=20GUP=20-=20still=20remains=20unr= esolved.=0D=0A>>>>=20(To=20be=20honest,=20I'm=20not=20quite=20sure=20how=20= such=20pages=20end=20up=20being=20pinned=20via=20GUP.=0D=0A>>>>=20=20=20Is= =20that=20the=20expected=20behavior,=20or=20could=20it=20possibly=20indicat= e=20a=20bug=20?)=0D=0A>>>=20The=20original=20problem=20arises=20from=20appl= ying=20CMA=20as=20guestOS's=20memory=0D=0A>>>=20slots=20for=20kvm=20which= =20use=20GUP=20to=20setup=20its=202nd=20stage=20mapping(HVA->PFN).=0D=0A>>>= =20You=20can=20check=20KVM=20code=20if=20you=20are=20interested.=0D=0A>>>= =0D=0A>>=20=0D=0A>>=20Thanks=20for=20the=20kind=20explanation.=20While=20I'= m=20not=20deeply=20familiar=20with=20KVM,=20my=20understanding=0D=0A>>=20is= =20that=20there=20are=20cases=20where=20GUP=20is=20used=20on=20CMA.=0D=0A>>= =20=0D=0A>>=20So=20does=20that=20mean=20pinning=20memory=20from=20the=20CMA= =20was=20actually=20intended=20to=20succeed=20?=0D=0A>=0D=0A>Careful:=20KVM= =20uses=20ordinary=20GUP,=20not=20GUP-longterm.=0D=0A=0D=0AHi.=20David=20an= d=20Zhaoyang=0D=0A=0D=0AIf=20possible,=20could=20you=20kindly=20explain=20t= he=20situation=20where=20the=201aaf8c122918=20was=20addeded?=0D=0AIf=20KVM= =20does=20not=20user=20FOLL_LONGTERM,=20then=20why=20the=20function,=0D=0Ac= ollect_longterm_unpinnable_folios,=20was=20changed=20at=20that=20time?=0D= =0A=0D=0AFirst=20of=20all,=20I'm=20not=20a=20KVM=20expert.=20After=20readin= g=20Zhaoyang's=20mail,=0D=0AI=20thought=20CMA=20free=20page=20was=20initial= ly=20allocated=20then=20migrated=20by=20FOLL_LONGTERM,=0D=0Aduring=20the=20= get_user_page=20for=20KVM's=20guest=20OS.=20If=20KVM=20does=20not=20use=20F= OLL_LONGTERM,=0D=0AI=20am=20confused.=0D=0A=0D=0AActually=20I=20did=20not= =20understand=20the=20infinite=20loop=20situation.=20I=20thought=20few=20ti= mes=20of=20-EAGAIN=0D=0Amight=20happen=20during=20the=20gup.=20But=20callin= g=20lru_add_drain_all=20by=20collect_longterm_unpinnable_folios=0D=0Awould= =20put=20the=20page=20to=20LRU.=20And=20other=20cma_alloc=20context=20or=20= migration=20context,=20I=20guess,=0D=0Aput=20the=20pages=20back=20to=20LRU= =20if=20there=20was=20race.=0D=0A=0D=0ABR=0D=0AJaewon=20Kim=0D=0A=0D=0A>=0D= =0A>--=20=0D=0A>Cheers,=0D=0A>=0D=0A>David=20/=20dhildenb=0D=0A>