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Tue, 05 Mar 2024 01:54:43 -0800 (PST) MIME-Version: 1.0 References: <20231025144546.577640-5-ryan.roberts@arm.com> <20240205095155.7151-1-v-songbaohua@oppo.com> <7061b9f4-b7aa-4dad-858c-53ee186c2d8f@arm.com> In-Reply-To: <7061b9f4-b7aa-4dad-858c-53ee186c2d8f@arm.com> From: Barry Song <21cnbao@gmail.com> Date: Tue, 5 Mar 2024 22:54:31 +1300 Message-ID: Subject: Re: [PATCH v3 4/4] mm: swap: Swap-out small-sized THP without splitting To: Ryan Roberts Cc: akpm@linux-foundation.org, david@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.com, shy828301@gmail.com, wangkefeng.wang@huawei.com, willy@infradead.org, xiang@kernel.org, ying.huang@intel.com, yuzhao@google.com, chrisl@kernel.org, surenb@google.com, hanchuanhua@oppo.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 2A8028000E X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: a1me8afkgww3nqw67rfnuyhtjuig7xkg X-HE-Tag: 1709632483-84456 X-HE-Meta: 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 GDzAW5FV 2Hb6/DuOI8W9hsA7tNIv+Bm9D6rAQxF74Di3283GqepicTTS67l6UEFvdRdcQfoMDyLsULBa65IGhf9tHJ6ZYCjmOFhkNWEN213GTrlipohCSQTz0EtA8L5J7lGOljfRcC+CAJ1blYeswNO0HbkI/6CNi173b0SJX2j8vZyf+lzw3CaDsjIi8ZN555kfYDTkbpzHBn4pNpqV33/cU4FkbElD+kMu91ZtffbZp0IrpjTFwxVzUmTkNOqlTIAX/Dvia0pF42r4SHYVcGpap0gHjtUvhPkFVzeTJLJmbSHiQO9xOd+MXCu9xu801S3df9ODf1RU073LANBcSrEhIR+eYwkgzSLx5e2H9tnIp0Wp0rBbB5wq/N6tdM6VeEc6CYP6X/kzyYCnUuWMVTDhUVqqXBh6Po8x+DHIFRFJRPaa+9TzXxxt/rM3a31jpKgo18dSyYL/vCzVGrzNuHLZHpuisOyX6iPIiKKofhIXtKyM9wV06iKvPCe9mJOL1+A== 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, Mar 5, 2024 at 10:00=E2=80=AFPM Ryan Roberts = wrote: > > Hi Barry, > > On 18/02/2024 23:40, Barry Song wrote: > > On Tue, Feb 6, 2024 at 1:14=E2=80=AFAM Ryan Roberts wrote: > >> > >> On 05/02/2024 09:51, Barry Song wrote: > >>> +Chris, Suren and Chuanhua > >>> > >>> Hi Ryan, > [...] > >> > > > > Hi Ryan, > > I am running into some races especially while enabling large folio swap= -out and > > swap-in both. some of them, i am still struggling with the detailed > > timing how they > > are happening. > > but the below change can help remove those bugs which cause corrupted d= ata. > > I'm getting quite confused with all the emails flying around on this topi= c. Here > you were reporting a data corruption bug and your suggested fix below is = the one > you have now posted at [1]. But in the thread at [1] we concluded that it= is not > fixing a functional correctness issue, but is just an optimization in som= e > corner cases. So does the corruption issue still manifest? Did you manage= to > root cause it? Is it a problem with my swap-out series or your swap-in se= ries, > or pre-existing? Hi Ryan, It is not a problem of your swap-out series, but a problem of my swap-in series. The bug in swap-in series is triggered by the skipped PTEs in the thread[1], but my swap-in code should still be able to cope with this situa= tion and survive it - a large folio might be partially but not completely unmap= ped after try_to_unmap_one(). I actually replied to you and explained all the details here[2], but guess you missed it :-) [1] https://lore.kernel.org/linux-mm/20240304103757.235352-1-21cnbao@gmail.= com/ [2] https://lore.kernel.org/linux-mm/CAGsJ_4zdh5kOG7QP4UDaE-wmLFiTEJC2PX-_L= xtOj=3DQrZSvkCA@mail.gmail.com/ apology this makes you confused. > > [1] https://lore.kernel.org/linux-mm/20240304103757.235352-1-21cnbao@gmai= l.com/ > > Thanks, > Ryan > Thanks Barry