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AJvYcCUeEjOkCZT30O0OuBKvOunn9IKgidPknnVBhWKGvyKhMIn4SRCVWNTEQ2/cgYHQG4IV/betvCoZw/ZHOOL+GZMGjUE= X-Gm-Message-State: AOJu0YzjUudKl/Y436jMYtKDFhFxh57iiKuWN/ljx0G6E7B66WecIRre g7ebU3Uzed1aCQTuEZZilZfJYh7Im/R6G38qGOTWhc7mql37p+xDvRjtQ1u0ugedFClIbnzh6Sj j8ZKbJ2y6XvTMFRqD7LFTCAecRb4= X-Google-Smtp-Source: AGHT+IHKiftvN1Jq/c5pWNkpCMblBsWG+z83c8TOftFKVld+yZI7GeYG1J7h/i9NaAg892W3YlLKdIRnlakXUTAaZW0= X-Received: by 2002:a05:6122:1693:b0:4ec:f4a2:69fc with SMTP id 71dfb90a1353d-4ee3f06bb4dmr12038754e0c.7.1718692295979; Mon, 17 Jun 2024 23:31:35 -0700 (PDT) MIME-Version: 1.0 References: <20240614100329.1203579-1-hch@lst.de> <20240614100329.1203579-2-hch@lst.de> <20240614112148.cd1961e84b736060c54bdf26@linux-foundation.org> <20240616085436.GA28058@lst.de> <20240617053201.GA16852@lst.de> <20240618055253.GA27945@lst.de> <20240618061340.GA28200@lst.de> In-Reply-To: <20240618061340.GA28200@lst.de> From: Barry Song <21cnbao@gmail.com> Date: Tue, 18 Jun 2024 18:31:24 +1200 Message-ID: Subject: Re: [PATCH] nfs: fix nfs_swap_rw for large-folio swap To: Christoph Hellwig Cc: Andrew Morton , Trond Myklebust , Anna Schumaker , Steve French , linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, linux-mm@kvack.org, Barry Song , Ryan Roberts Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: 76f5o1ymzbzbfrmku1cfhg9scu7z6oh5 X-Rspamd-Queue-Id: 722C5100002 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1718692297-350032 X-HE-Meta: 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 zDnx1iNl kfSHfFJkVMTevJawIiMns80Jygy7B9oM7CJb64vx+RQ6838XoTPhExtn4Nw4R52pp0mn433ZCFDx66KbW8JDbqO7PvLdYwCqaXIDsE7EitoqfnZlVRQjv1jE3rumX5J44iBgi77g1oTXQX20OEzYXAeZHU+J4l95s0FXB8v6Hq9DMESI9eZj8sEd2XM4EyXQ5opw6HoftRR6Nel2vqxK5EDI/jvTz4dfxqw15rF1Kyf8MmppsMloaE74dqOcKFtTFZKs6m0Z+S+ALaS0QZAcZ/rQ//e3qHkfPFkhWidvVwJeFV6+YTfcq/rWeAyoE41J8GzIeZ0JDkLbsIK529SkqrFYGYU0Ov5cPSyiabdZv0xglwe6IwVl9PZaOMFH9PxihztJGwFPJRUKXN0ezEBKVbUSw1zhMTjkH5GSwzqTgKojeh3w= 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 Tue, Jun 18, 2024 at 6:13=E2=80=AFPM Christoph Hellwig wrot= e: > > On Tue, Jun 18, 2024 at 06:05:33PM +1200, Barry Song wrote: > > Yes, that was exactly what I missed. I then figured it out, reproduced > > the issue, > > and discovered that the root cause was unrelated to large folios. It > > was actually > > due to a batched bio plugging optimization from 2022. You can find the = new patch > > here: > > > > https://lore.kernel.org/linux-mm/20240617220135.43563-1-21cnbao@gmail.c= om/ > > I don't really see any point in keeping the VM_BUG_ON. The underlying > direct I/O code doesn't really care about the size at all. I am perfectly fine with dropping the VM_BUG/WARN. I was keeping it for debugging purposes while we add mTHP swapout support for the swapfile. Large folios m= ight be in bio vec, this can help verify things are still normal after having large folios there. But I agree that this is not important for the NFS code itself. I can add this warning locally for debugging when needed.