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AJvYcCWPthU/6omTv2QZpgFYO1g9zyXDW7qU0HXhfw5JDw982v05DDYuERYf9bL+DIRGOXNbJ1j5ihW7tuXLnrjoYydi3F0= X-Gm-Message-State: AOJu0Yy4QfOuWKtHWAH+BJ6lr5zbUyzqgqYKMX7S12PWW6LCYAKvG3+u 5mWMsO8COtfLmIKTdoh0aAtaiqI1xyt/YfPX85tPdMCMG7FRjSAE22OswHIr/4IWa/XDOVf0/pW kb5ZptRl5BPKbKsDH7kXkExc3Wrg= X-Google-Smtp-Source: AGHT+IFrF+peqaqFCCGF16X35g5CpPH1YFC+SDa8pFRJeYm9hZc1mBc9E20qaewP7CYxn4hnM1CjsauVZLyC504KnbE= X-Received: by 2002:a2e:954e:0:b0:2d7:1ce5:3e24 with SMTP id t14-20020a2e954e000000b002d71ce53e24mr5521022ljh.34.1712039631218; Mon, 01 Apr 2024 23:33:51 -0700 (PDT) MIME-Version: 1.0 References: <20240401081734.1433755-1-zhaoyang.huang@unisoc.com> In-Reply-To: From: Zhaoyang Huang Date: Tue, 2 Apr 2024 14:33:39 +0800 Message-ID: Subject: Re: [PATCHv2 1/1] mm: fix unproperly folio_put by changing API in read_pages To: Matthew Wilcox Cc: "zhaoyang.huang" , Andrew Morton , NeilBrown , linux-mm@kvack.org, linux-kernel@vger.kernel.org, steve.kang@unisoc.com, Christoph Hellwig Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: B57AB120002 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: xxt5qphw9au49xn3soxqnd159x66fwib X-HE-Tag: 1712039633-449053 X-HE-Meta: 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 L/xuFGpD KYrqeFR6k3VNTahFtV7LcQ6aXAMFOaf4btCeUmAs6DxN4tAGz1g4V16tYmfMuKbRKpAjMsHYUS8w2CLY= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000009, 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 Tue, Apr 2, 2024 at 8:34=E2=80=AFAM Matthew Wilcox = wrote: > > On Mon, Apr 01, 2024 at 04:17:34PM +0800, zhaoyang.huang wrote: > > From: Zhaoyang Huang > > > > An VM_BUG_ON in step 9 of [1] could happen as the refcnt is dropped > > unproperly during the procedure of read_pages()->readahead_folio->folio= _put. > > This is introduced by commit 9fd472af84ab ("mm: improve cleanup when > > ->readpages doesn't process all pages")'. > > This patch is no less bullshit than the last time you posted it. > I explained why here: > https://lore.kernel.org/linux-mm/ZgQRtQ60mrvOUKXo@casper.infradead.org/ Yes. I get your point in your previous feedback. Could you please check the timing sequence in v2's commit message, where the folio_lock failed to prevent the race from happening. I also would like to insist that the refcnt got from alloc_pages just paired with the one which is checked in __remove_mapping but any other folio_put. The sequence of read_pages->readahead_folio->folio_put happens to be right when no race and then frees the folio immediatly.