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AJvYcCXXtOC5SbRLsKlWsQOmL23ejTZuCzZ56m+fY5+e01OUrWnsLWWhYpWkakFxC+2xXpR3Ru40x5UBc9XkqHpQWNWD8iM= X-Gm-Message-State: AOJu0YwYQNtFvPJoqZUn7nClvjjwq3Wr3odEqbglNM3dNU/2Ojbnksm3 vTt1QE9Xb+A3kLkRdqYuO18eiEgbW/PqaLxv1kqUpPoPzIVZaLIyV5x9TE8UM+1di9mz09+exhR BjqcOcKaEXrQ2VShitXVl0u53OPMm1VKCTFIr X-Google-Smtp-Source: AGHT+IGws2WNiAW+CHMNO5l3bV/NuBf94dey6Xz+Fqz4NyttzRBZUtmmXF+78525k26piEhTbhFpGostqyGGy5wNbQU= X-Received: by 2002:a19:ca5d:0:b0:52c:81b2:ad2a with SMTP id 2adb3069b0e04-52ca6e65709mr540514e87.24.1718317526706; Thu, 13 Jun 2024 15:25:26 -0700 (PDT) MIME-Version: 1.0 References: <3c11000dd6c1df83015a8321a859e9775ebbc23e.1718266112.git.baolin.wang@linux.alibaba.com> In-Reply-To: <3c11000dd6c1df83015a8321a859e9775ebbc23e.1718266112.git.baolin.wang@linux.alibaba.com> From: Yosry Ahmed Date: Thu, 13 Jun 2024 15:24:48 -0700 Message-ID: Subject: Re: [PATCH] mm: shmem: fix getting incorrect lruvec when replacing a shmem folio To: Baolin Wang Cc: akpm@linux-foundation.org, hughd@google.com, hannes@cmpxchg.org, nphamcs@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: w3pgeqjj5emqh977g7c734m57qk57usp X-Rspam-User: X-Rspamd-Queue-Id: B177814000B X-Rspamd-Server: rspam02 X-HE-Tag: 1718317528-561927 X-HE-Meta: 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 cQgprS5W xAp6199CtYijyFOr2znaISFdaERDd9yE7Q+NXAxIULLEQ+b/RJ58N1dD7UiCZc6MdFEru19Nj4H6Bal8yhqMQ20lCXNZPkhArwMNEiVKTcmgECbPohVGVYLm/1qYjygICKstKx7+Xtg2GHutLGSvioYfT04UywEufmSAAaqVM1QkcWq7Qae0D4Xzt6Z1se39X9XR/ X-Bogosity: Ham, tests=bogofilter, spamicity=0.000007, 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 1:21=E2=80=AFAM Baolin Wang wrote: > > When testing shmem swapin, I encountered the warning below on my machine. > The reason is that replacing an old shmem folio with a new one causes > mem_cgroup_migrate() to clear the old folio's memcg data. As a result, > the old folio cannot get the correct memcg's lruvec needed to remove itse= lf > from the LRU list when it is being freed. This could lead to possible ser= ious > problems, such as LRU list crashes due to holding the wrong LRU lock, and > incorrect LRU statistics. > > To fix this issue, we can fallback to use the mem_cgroup_replace_folio() > to replace the old shmem folio. > > [ 5241.100311] page: refcount:0 mapcount:0 mapping:0000000000000000 index= :0x0 pfn:0x5d9960 > [ 5241.100317] head: order:4 mapcount:0 entire_mapcount:0 nr_pages_mapped= :0 pincount:0 > [ 5241.100319] flags: 0x17fffe0000040068(uptodate|lru|head|swapbacked|nod= e=3D0|zone=3D2|lastcpupid=3D0x3ffff) > [ 5241.100323] raw: 17fffe0000040068 fffffdffd6687948 fffffdffd69ae008 00= 00000000000000 > [ 5241.100325] raw: 0000000000000000 0000000000000000 00000000ffffffff 00= 00000000000000 > [ 5241.100326] head: 17fffe0000040068 fffffdffd6687948 fffffdffd69ae008 0= 000000000000000 > [ 5241.100327] head: 0000000000000000 0000000000000000 00000000ffffffff 0= 000000000000000 > [ 5241.100328] head: 17fffe0000000204 fffffdffd6665801 ffffffffffffffff 0= 000000000000000 > [ 5241.100329] head: 0000000a00000010 0000000000000000 00000000ffffffff 0= 000000000000000 > [ 5241.100330] page dumped because: VM_WARN_ON_ONCE_FOLIO(!memcg && !mem_= cgroup_disabled()) > [ 5241.100338] ------------[ cut here ]------------ > [ 5241.100339] WARNING: CPU: 19 PID: 78402 at include/linux/memcontrol.h:= 775 folio_lruvec_lock_irqsave+0x140/0x150 > [...] > [ 5241.100374] pc : folio_lruvec_lock_irqsave+0x140/0x150 > [ 5241.100375] lr : folio_lruvec_lock_irqsave+0x138/0x150 > [ 5241.100376] sp : ffff80008b38b930 > [...] > [ 5241.100398] Call trace: > [ 5241.100399] folio_lruvec_lock_irqsave+0x140/0x150 > [ 5241.100401] __page_cache_release+0x90/0x300 > [ 5241.100404] __folio_put+0x50/0x108 > [ 5241.100406] shmem_replace_folio+0x1b4/0x240 > [ 5241.100409] shmem_swapin_folio+0x314/0x528 > [ 5241.100411] shmem_get_folio_gfp+0x3b4/0x930 > [ 5241.100412] shmem_fault+0x74/0x160 > [ 5241.100414] __do_fault+0x40/0x218 > [ 5241.100417] do_shared_fault+0x34/0x1b0 > [ 5241.100419] do_fault+0x40/0x168 > [ 5241.100420] handle_pte_fault+0x80/0x228 > [ 5241.100422] __handle_mm_fault+0x1c4/0x440 > [ 5241.100424] handle_mm_fault+0x60/0x1f0 > [ 5241.100426] do_page_fault+0x120/0x488 > [ 5241.100429] do_translation_fault+0x4c/0x68 > [ 5241.100431] do_mem_abort+0x48/0xa0 > [ 5241.100434] el0_da+0x38/0xc0 > [ 5241.100436] el0t_64_sync_handler+0x68/0xc0 > [ 5241.100437] el0t_64_sync+0x14c/0x150 > [ 5241.100439] ---[ end trace 0000000000000000 ]--- > > Fixes: 85ce2c517ade ("memcontrol: only transfer the memcg data for migrat= ion") > Signed-off-by: Baolin Wang > --- > mm/shmem.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/shmem.c b/mm/shmem.c > index 99bd3c34f0fb..4acaf02bfe44 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -1908,7 +1908,7 @@ static int shmem_replace_folio(struct folio **folio= p, gfp_t gfp, > xa_lock_irq(&swap_mapping->i_pages); > error =3D shmem_replace_entry(swap_mapping, swap_index, old, new)= ; > if (!error) { > - mem_cgroup_migrate(old, new); > + mem_cgroup_replace_folio(old, new); The comment above the definition of mem_cgroup_replace_folio() needs to be updated with this change. It mentions that it is only used in replace_page_cache_folio(), which is no longer true. > __lruvec_stat_mod_folio(new, NR_FILE_PAGES, 1); > __lruvec_stat_mod_folio(new, NR_SHMEM, 1); > __lruvec_stat_mod_folio(old, NR_FILE_PAGES, -1); > -- > 2.39.3 > >