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AJvYcCUAoa4mtR81ZahW5Us3/6WFFAZiyf0shtUTETQC0pvBSenhLkeZiw5QE0OaNYvbuePw+w6pi25Whg==@kvack.org X-Gm-Message-State: AOJu0YxVb/4PX8fC9ud3ySNbXnkTHHakyW/MwPPlBNE3IwlpPhtp5i69 +jc3ECOWQHyK3IBlHi0d8As04DtScWHkqszWJMZ/9imxlFjlgDNc4Q07/H6A/Rls7/OJerMoLqk 1YL52j0vpQA4FfQ5QhdN9AUqrdlM= X-Google-Smtp-Source: AGHT+IEJ1YZX/IPynYGWqcY7XfO8Q+lX8kNXo13gm7vkOErWnlLDKM2zYGmEjYvPV68EmPEYItvAuXF8074qPtKaxpQ= X-Received: by 2002:ac8:5fcd:0:b0:461:6054:52c with SMTP id d75a77b69052e-4630938866amr58248991cf.29.1731104456457; Fri, 08 Nov 2024 14:20:56 -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> <2ecmqokellladmioa5rvw57lqbz3ouevx5q5weyydjius3cu2s@vl3siu2b3gs6> In-Reply-To: <2ecmqokellladmioa5rvw57lqbz3ouevx5q5weyydjius3cu2s@vl3siu2b3gs6> From: Joanne Koong Date: Fri, 8 Nov 2024 14:20:45 -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: rspam06 X-Rspamd-Queue-Id: 4D8CD4000B X-Stat-Signature: u1toh1y7yfcg4my4tn4e7k45oo91fi9k X-Rspam-User: X-HE-Tag: 1731104419-771064 X-HE-Meta: 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 vw83RHYC AWLolad01BdZ0K5ZStOF2y4M0WXwpMrrs7KzZksV4z2m7bAo/TG7ZY1jMvA1l10VwiBQjjgvQOiMELifLlkLbhy1MLlUklbNyRh+g/Cw/oTF9Wq7WNTpRAoCfWPyH3+lDt+JrEOyJSwkZ05Pc8p09jwMFYOL1LgdSkssv37OsHKXQA3brPScaKkOQZHZaZY1IscKdOtRW2W+UvMnr1VREZLrVlkB66oY8k2JgUr+LUsEiJYHydV1T6+ZQddzGwJh3JvjCOv8FQqD19FvkOiQycrJ7DcAW1ga4n6uH7aTFOE5Yx1GceJLUYNtY+BAcoHk3fx+3cb9oNPuNCKsxybSFyn3n0B14TSNEdCu+9E8V8reacrqVfz1ildfD2H6W8UQoshEcEqlbVRxenA2wc98sOFmMBvP3LtjNu/sQOblemLbfr30/ODV3kNYTKw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.006909, 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 2:16=E2=80=AFPM Shakeel Butt wrote: > > On Fri, Nov 08, 2024 at 01:42:15PM -0800, Joanne Koong wrote: > > 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 = forever if > > > > > > > the migration fails. Add a return value for do_migrate_range(= ), and > > > > > > > allow offline_page() to try migrating pages 5 times before er= roring > > > > > > > out, similar to how migration failures in __alloc_contig_migr= ate_range() > > > > > > > is handled. > > > > > > > > > > > > I'm curious if this could cause unexpected behavioral differenc= es to memory > > > > > > hotplugging users, and how '5' is chosen. Could you please enl= ighten 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= -15aa-4093-a573-3bfd8da14ff1@fujitsu.com/T/#mdda39b2956a11c46f8da8796f9612a= c007edbdab > > > > > > > > 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? > > I think irrespective of the source of the hotplug, the current behavior > of infinite retries in some cases is documented and kind of expected, so > no need to fix it. (Though I don't know all the source of hotplug.) > Awesome, this sounds great. Thanks! >