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AJvYcCVdqle5lGoytR8drgca+iRtxx92snMeRihseTeD1mpobXqYiagvOurCu1vgZMDkDIUkaAiAz3Pq2A==@kvack.org X-Gm-Message-State: AOJu0YzIYaLtcPdtSza/+kbXCZ1vd4QxMiSiebrUhRsXyigJ+Zc9Hafv D0fDsNLCj88ZEpqgXlug3T2qEQymIRxW06fKouNPNSoBDd1hSJrb54E3LzE1tBS54WxRJ8EF/RB gYIJK+wHqbd5ZriT243K80VZ5GXY= X-Google-Smtp-Source: AGHT+IHq100ugMRlsPPoszRN4yErc4jmWDRnK4I2csN1bK6ma3n38X65oAkX29Q25TVJz5DOX18EFIsueG++B03s5oc= X-Received: by 2002:a05:622a:5919:b0:460:850d:cbda with SMTP id d75a77b69052e-4630938b6f7mr70858491cf.31.1731102146347; Fri, 08 Nov 2024 13:42:26 -0800 (PST) MIME-Version: 1.0 References: <20241108173309.71619-1-sj@kernel.org> <04020bb7-5567-4b91-a424-62c46f136e2a@redhat.com> <4d2062bd-3cf3-4488-8dfc-b0aa672ee786@redhat.com> In-Reply-To: From: Joanne Koong Date: Fri, 8 Nov 2024 13:42:15 -0800 Message-ID: Subject: Re: [PATCH v4 4/6] mm/memory-hotplug: add finite retries in offline_pages() if migration fails To: Shakeel Butt Cc: David Hildenbrand , SeongJae Park , miklos@szeredi.hu, linux-fsdevel@vger.kernel.org, jefflexu@linux.alibaba.com, josef@toxicpanda.com, linux-mm@kvack.org, bernd.schubert@fastmail.fm, kernel-team@meta.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 4555DA0033 X-Stat-Signature: 4ossrpj4cgyda7mgtjyrc1umrszk3kb6 X-Rspam-User: X-HE-Tag: 1731102109-39179 X-HE-Meta: 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 KLVFB9e8 8SnzgMcI2fd1n3o5Bo1Lmi7n+XFLEXHJloer5VmvcpFpYSvLEfe9x6z6rmf4bQWKceEe3IijuVZuCJy68hy4P5apwrAVWKjyN1Y42Iijoqfwhdkzl6saqeoRJaAdHmVsul/t8RD6r7ml2c0xGR10ySUdbi55hct4ECrmF6gajX0bOgTI9qkPXbhSTBqX7ciJ0LHUXJTonlhYXoRY5YCQ3QqSNj3tUnB7sH0Z1j3cXta2o2te0RDYwYCRB6w9jpbvPhrHhC3S6CyUvYKmgbQY4zp2qnY7J5wIIcGy1DvCC0F1wmyJdP5v88nRjrLo++kIJ4BqylMap2vNUtlTAByFSgSl6QUECiiwTviV2LO5wIIXVhiCqx+7149iccu8L9MvARFM2xqZfkF/b+SLg5tZzTxeR2Sa3HeeZtlLsXsEcik7rcjCf8qybHPmznA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.007100, 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 Fri, Nov 8, 2024 at 1:27=E2=80=AFPM Shakeel Butt wrote: > > On Fri, Nov 08, 2024 at 08:00:25PM +0100, David Hildenbrand wrote: > > On 08.11.24 19:56, David Hildenbrand wrote: > > > On 08.11.24 18:33, SeongJae Park wrote: > > > > + David Hildenbrand > > > > > > > > On Thu, 7 Nov 2024 15:56:12 -0800 Joanne Koong wrote: > > > > > > > > > In offline_pages(), do_migrate_range() may potentially retry fore= ver if > > > > > the migration fails. Add a return value for do_migrate_range(), a= nd > > > > > allow offline_page() to try migrating pages 5 times before errori= ng > > > > > out, similar to how migration failures in __alloc_contig_migrate_= range() > > > > > is handled. > > > > > > > > I'm curious if this could cause unexpected behavioral differences t= o memory > > > > hotplugging users, and how '5' is chosen. Could you please enlight= en me? > > > > > > > > > > I'm wondering how much more often I'll have to nack such a patch. :) > > > > A more recent discussion: https://lore.kernel.org/linux-mm/52161997-15a= a-4093-a573-3bfd8da14ff1@fujitsu.com/T/#mdda39b2956a11c46f8da8796f9612ac007= edbdab > > > > Long story short: this is expected and documented > > Thanks David for the background. > > Joanne, simply drop this patch. It is not required for your series. Awesome, I'm happy to drop this patch. Just curious though - don't we need this in order to mitigate the scenario where if an unprivileged fuse server never completes writeback, we don't run into this infinite loop? Or is it that memory hotplugging is always initiated from userspace so if it does run into an infinite loop (like also in that thread David linked), userspace is responsible for sending a signal to terminate it? Thanks, Joanne