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AJvYcCVVsrggFuz154C/GeuYNuBkHPAX3FHnvzjU0XjrURt27CaeisUqkMbS7RSSmsrR0hQ1O3difR27xCMvdAjJ+FSqGNs= X-Gm-Message-State: AOJu0YylnQOzVgiKpbaCYSs/50q8+sJ/UVo1DokAxn4iiisRIENMFAtQ P1k/Oh9MQqXLK2dJSwB7POFkbr0jk6TtksAKkaSxjJMSuFlzvQi/hQWWXYYRFDm10E4w2t5hheI fHZQd7U/CArRbRHWwpyNuojBBeQs= X-Google-Smtp-Source: AGHT+IE1w1nDx6mY9G/9ghDu/1JG51Vp0gA5yWIl2rbWqTFgn3CtRasXMUQ7coTwSiK6yvvSZThTDQ3bTsBzgmRBuGk= X-Received: by 2002:a05:6122:c89:b0:4ec:f3b4:6283 with SMTP id 71dfb90a1353d-4ee3fe42694mr2086481e0c.6.1718351779848; Fri, 14 Jun 2024 00:56:19 -0700 (PDT) MIME-Version: 1.0 References: <20240613000721.23093-1-21cnbao@gmail.com> <20240613000721.23093-4-21cnbao@gmail.com> In-Reply-To: From: Barry Song <21cnbao@gmail.com> Date: Fri, 14 Jun 2024 19:56:07 +1200 Message-ID: Subject: Re: [PATCH RFC 3/3] mm: remove folio_test_anon(folio)==false path in __folio_add_anon_rmap() To: David Hildenbrand Cc: akpm@linux-foundation.org, linux-mm@kvack.org, chrisl@kernel.org, linux-kernel@vger.kernel.org, mhocko@suse.com, ryan.roberts@arm.com, baolin.wang@linux.alibaba.com, yosryahmed@google.com, shy828301@gmail.com, surenb@google.com, v-songbaohua@oppo.com, willy@infradead.org, ying.huang@intel.com, yuzhao@google.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: D899714000E X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 4joqprw8te1mftetc4kdwh6d9h58eif3 X-HE-Tag: 1718351780-301797 X-HE-Meta: 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 Z5yocN2f DjvjFO7dbMPSyt8JjmqzeIOu4NHK9kPnuR7ohpWiWGAW+Cf3TQmIgF5rdIbmHkBC119qMu1VxapTcNASgXhYEKZ30AbZb8pfWuKKyklc8AVHLA0aLh1VRd0eEsZE0xdGCk0iTNo+wJ645csKseb11/vFApWldiJrPrZujO2yD8T821RBNC8h7d754ncrroaRwvk+RRDXxEXO/3rEALS0jGGRfQi5zqEq8M0PLcKlGDhzKVKyCriIbCExnPlruY6tKqI6JkP7f2Sk0MLpsx+KxR5vT5aJ0u+aAA0B2y1ASw0sJr8COPwlUFjRua20tVglXVAqvj1kTw2v1EFErKTlqR1frPn9OwXtHIBeUhFBeNWuJ33NeXMgNk2i7IqaNa19D77pUe/jk09qv7u9+a7fed6SQP9HfluF/0bBh56syS/wSWphntBSuaqokX//Uir0PxBMN 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 Thu, Jun 13, 2024 at 9:12=E2=80=AFPM David Hildenbrand wrote: > > On 13.06.24 11:06, Barry Song wrote: > > On Thu, Jun 13, 2024 at 8:49=E2=80=AFPM David Hildenbrand wrote: > >> > >> On 13.06.24 10:46, Barry Song wrote: > >>> On Thu, Jun 13, 2024 at 12:08=E2=80=AFPM Barry Song <21cnbao@gmail.co= m> wrote: > >>>> > >>>> From: Barry Song > >>>> > >>>> The folio_test_anon(folio)=3D=3Dfalse case within do_swap_page() has= been > >>>> relocated to folio_add_new_anon_rmap(). Additionally, two other call= ers > >>>> consistently pass anonymous folios. > >>>> > >>>> stack 1: > >>>> remove_migration_pmd > >>>> -> folio_add_anon_rmap_pmd > >>>> -> __folio_add_anon_rmap > >>>> > >>>> stack 2: > >>>> __split_huge_pmd_locked > >>>> -> folio_add_anon_rmap_ptes > >>>> -> __folio_add_anon_rmap > >>>> > >>>> __folio_add_anon_rmap() only needs to handle the cases > >>>> folio_test_anon(folio)=3D=3Dtrue now. > >>> > >>> My team reported a case where swapoff() is calling > >>> folio_add_anon_rmap_pte *not* folio_add_anon_rmap_ptes > >>> with one new anon (!folio_test_anon(folio)). > >>> > >>> I will double check all folio_add_anon_rmap_pte() cases. > >> > >> Right, swapoff() path is a bit special (e.g., we don't do any kind of > >> batching on the swapoff() path). > >> > >> But we should never get a new large anon folio there, or could that no= w > >> happen? > > > > My team encountered the following issue while testing this RFC > > series on real hardware. Let me take a look to identify the > > problem. > > > > [ 261.214195][T11285] page:000000004cdd779e refcount:4 mapcount:1 > > mapping:00000000ba142c22 index:0x1 pfn:0x1b30a6 > > [ 261.214213][T11285] memcg:ffffff8003678000 > > [ 261.214217][T11285] aops:swap_aops > > [ 261.214233][T11285] flags: > > 0x2000000000081009(locked|uptodate|owner_priv_1|swapbacked|zone=3D1|kas= antag=3D0x0) > > [ 261.214241][T11285] page_type: 0x0() > > [ 261.214246][T11285] raw: 2000000000081009 0000000000000000 > > dead000000000122 0000000000000000 > > [ 261.214251][T11285] raw: 0000000000000001 00000000000d84b3 > > 0000000400000000 ffffff8003678000 > > [ 261.214254][T11285] page dumped because: > > VM_WARN_ON_FOLIO(!folio_test_anon(folio)) > > [ 261.214257][T11285] page_owner tracks the page as allocated > > [ 261.214260][T11285] page last allocated via order 0, migratetype > > Movable, gfp_mask 0x2140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid > > 11285, tgid 11285 (swapoff), ts 261214177545, free_ts 261151875699 > > [ 261.214268][T11285] post_alloc_hook+0x1b8/0x1c0 > > [ 261.214284][T11285] prep_new_page+0x28/0x13c > > [ 261.214291][T11285] get_page_from_freelist+0x198c/0x1aa4 > > [ 261.214298][T11285] __alloc_pages+0x15c/0x330 > > [ 261.214304][T11285] __folio_alloc+0x1c/0x4c > > [ 261.214310][T11285] __read_swap_cache_async+0xd8/0x48c > > [ 261.214320][T11285] swap_cluster_readahead+0x158/0x324 > > [ 261.214326][T11285] swapin_readahead+0x64/0x448 > > [ 261.214331][T11285] __arm64_sys_swapoff+0x6ec/0x14b0 > > [ 261.214337][T11285] invoke_syscall+0x58/0x114 > > [ 261.214353][T11285] el0_svc_common+0xac/0xe0 > > [ 261.214360][T11285] do_el0_svc+0x1c/0x28 > > [ 261.214366][T11285] el0_svc+0x38/0x68 > > [ 261.214372][T11285] el0t_64_sync_handler+0x68/0xbc > > [ 261.214376][T11285] el0t_64_sync+0x1a8/0x1ac > > [ 261.214381][T11285] page last free pid 90 tgid 90 stack trace: > > [ 261.214386][T11285] free_unref_page_prepare+0x338/0x374 > > [ 261.214395][T11285] free_unref_page_list+0x84/0x378 > > [ 261.214400][T11285] shrink_folio_list+0x1234/0x13e4 > > [ 261.214409][T11285] evict_folios+0x1458/0x19b4 > > [ 261.214417][T11285] try_to_shrink_lruvec+0x1c8/0x264 > > [ 261.214422][T11285] shrink_one+0xa8/0x234 > > [ 261.214427][T11285] shrink_node+0xb38/0xde0 > > [ 261.214432][T11285] balance_pgdat+0x7a4/0xdb4 > > [ 261.214437][T11285] kswapd+0x290/0x4e4 > > [ 261.214442][T11285] kthread+0x114/0x1bc > > [ 261.214459][T11285] ret_from_fork+0x10/0x20 > > [ 261.214477][T11285] ------------[ cut here ]------------ > > [ 261.214480][T11285] WARNING: CPU: 3 PID: 11285 at mm/rmap.c:1305 > > folio_add_anon_rmap_ptes+0x2b4/0x330 > > > > [ 261.215403][T11285] pstate: 63400005 (nZCv daif +PAN -UAO +TCO +DIT > > -SSBS BTYPE=3D--) > > [ 261.215423][T11285] pc : folio_add_anon_rmap_ptes+0x2b4/0x330 > > [ 261.215428][T11285] lr : folio_add_anon_rmap_ptes+0x2b4/0x330 > > [ 261.215433][T11285] sp : ffffffc0a7dbbbf0 > > [ 261.215437][T11285] x29: ffffffc0a7dbbbf0 x28: ffffff8040860a08 > > x27: ffffff80db480000 > > [ 261.215445][T11285] x26: fffffffe04cc2980 x25: ffffff808f77f120 > > x24: 0000007b44941000 > > [ 261.215452][T11285] x23: 0000000000000001 x22: 0000000000000001 > > x21: fffffffe04cc2980 > > [ 261.215459][T11285] x20: ffffff80db480000 x19: fffffffe04cc2980 > > x18: ffffffed011dae80 > > [ 261.215465][T11285] x17: 0000000000000001 x16: ffffffffffffffff > > x15: 0000000000000004 > > [ 261.215471][T11285] x14: ffffff82fb73fac0 x13: 0000000000000003 > > x12: 0000000000000003 > > [ 261.215476][T11285] x11: 00000000fffeffff x10: c0000000fffeffff x9 > > : 0d46c0889b468e00 > > [ 261.215483][T11285] x8 : 0d46c0889b468e00 x7 : 545b5d3935343431 x6 > > : 322e31363220205b > > [ 261.215489][T11285] x5 : ffffffed013de407 x4 : ffffffed00698967 x3 > > : 0000000000000000 > > [ 261.215495][T11285] x2 : 0000000000000000 x1 : ffffffc0a7dbb8c0 x0 > > : ffffff8068c15c80 > > [ 261.215501][T11285] Call trace: > > [ 261.215504][T11285] folio_add_anon_rmap_ptes+0x2b4/0x330 > > [ 261.215509][T11285] __arm64_sys_swapoff+0x8cc/0x14b0 > > [ 261.215516][T11285] invoke_syscall+0x58/0x114 > > [ 261.215526][T11285] el0_svc_common+0xac/0xe0 > > [ 261.215532][T11285] do_el0_svc+0x1c/0x28 > > [ 261.215539][T11285] el0_svc+0x38/0x68 > > [ 261.215544][T11285] el0t_64_sync_handler+0x68/0xbc > > [ 261.215548][T11285] el0t_64_sync+0x1a8/0x1ac > > [ 261.215552][T11285] ---[ end trace 0000000000000000 ]--- > > Ah, yes. in unuse_pte(), you'll have to do the right thing if > !folio_test(anon) before doing the folio_add_anon_rmap_pte(). > > You might have a fresh anon folio in the swapcache that was never mapped > (hopefully order-0, otherwise we'd likely be in trouble). Yes. It is order-0 [ 261.214260][T11285] page last allocated via order 0, migratetype Otherwise, we would have encountered this VM_WARN_ON_FOLIO? __folio_add_anon_rmap() { ... VM_WARN_ON_FOLIO(folio_test_large(folio) && level !=3D RMAP_LEVEL_PMD, folio); ... } Given that nobody has ever reported this warning, I assume all callers using folio_add_anon_rmap_pte(s) are right now safe to move to ? if (!folio_test_anon(folio)) folio_add_new_anon_rmap(folio, vma, address, rmap_flags); else folio_add_anon_rmap_pte(s) > > -- > Cheers, > > David / dhildenb > Thanks Barry