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AJvYcCWgdMzKnDFket2kRwcXFeE0N+OpSDS7fV5mIRMnZhAnZ4Qdq3CMu74ssui6WHKyA6ndwTl/J28SNPHZKy4=@vger.kernel.org X-Gm-Message-State: AOJu0Yxde7Z4vTNxTt7Eujk07633m2s8J2bnXIvm7JGUKJHpO/IUgpSS Gxv0PqedRhqWxoSiwlhV4ossnChhRUnSysm25OUIYX/d3gIWZG97biyOqzFpWZ9f4gtM+52ORER yj/hSerWOs3tmLxyNgJ8Yj5bNfmGQ2MsjUoSsuw== X-Gm-Gg: ASbGncu/qusoCs8hLzRk4XcNJRNv37SEfMSrn6OIuYUPXPJk/lmylCzcpmavSPbdvGP PF1lBZf1dEDuQkpIna8zp+GWSx9SxDQu85LqDwbTKMB5L2VDoK0B3NZFnmofUvHeYQrWcaYx9FI d3Flbf3vPZbn+cuZ7cWQ1W/pn6chpDI6kakg== X-Google-Smtp-Source: AGHT+IGGD6454gToVDn/IoUIEfR1+ItsL/HISjK3ehJg9NVRI5QeW5I9RnXyLdaCHCAikYx5stTntOwf9Gs+iVc7lQw= X-Received: by 2002:a5d:5985:0:b0:39e:cbd2:986b with SMTP id ffacd0b85a97d-39ee2729edcmr926257f8f.7.1744761462016; Tue, 15 Apr 2025 16:57:42 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20250324-tp4129-v1-0-95a747b4c33b@kernel.org> <20250324-tp4129-v1-3-95a747b4c33b@kernel.org> <20250410085137.GE1868505-mkhalfella@purestorage.com> <738a41ca-3e4a-48df-9424-2950e6efc082@grimberg.me> <4cd2cbb4-95ff-4f3b-b33b-9c066147d12b@flourine.local> <4c334216-74d7-4a30-add1-67b6e023d8d2@grimberg.me> <8ac6cc96-8877-4ddc-b57a-2a096f446a4c@grimberg.me> In-Reply-To: <8ac6cc96-8877-4ddc-b57a-2a096f446a4c@grimberg.me> From: Randy Jennings Date: Tue, 15 Apr 2025 16:57:29 -0700 X-Gm-Features: ATxdqUGpEGX9YZAHGCTlBMQHQBANn-EtpiIizt1Virtao_yXmWw0UoGELM1OZAU Message-ID: Subject: Re: [PATCH RFC 3/3] nvme: delay failover by command quiesce timeout To: Sagi Grimberg Cc: Daniel Wagner , Mohamed Khalfella , Daniel Wagner , Christoph Hellwig , Keith Busch , Hannes Reinecke , John Meneghini , linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, Apr 15, 2025 at 4:35=E2=80=AFPM Sagi Grimberg wr= ote: > > > >> What I meant was that the user can no longer set kato to be arbitraril= y > >> long when we > >> now introduce failover dependency on it. > >> > >> We need to set a sane maximum value that will failover in a reasonable > >> timeframe. > >> In other words, kato cannot be allowed to be set by the user to 60 > >> minutes. While we didn't > >> care about it before, now it means that failover may take 60+ minutes. > >> > >> Hence, my request to set kato to a max absolute value of seconds. My > >> vote was 10 (2x of the default), > >> but we can also go with 30. > > Adding a maximum value for KATO makes a lot of sense to me. This will > > help keep us away from a hung task timeout when the full delay is > > taken into account. 30 makes sense to me from the perspective that > > the maximum should be long enough to handle non-ideal situations > > functionally, but not a value that you expect people to use regularly. > > > > I think CQT should have a maximum allowed value for similar reasons. > > If we do clamp down on the CQT, we could be opening ourselves to the > > target not completely cleaning up, but it keeps us from a hung task > > timeout, and _any_ delay will help most of the time. > > CQT comes from the controller, and if it is high, it effectively means > that the > controller cannot handle faster failover reliably. So I think we should > leave it > as is. It is the vendor problem. Okay, that is one way to approach it. However, because of the hung task issue, we would be allowing the vendor to panic the initiator with a hung task. Until CCR, and without implementing other checks (for events which might not happen), this hung task would happen on every messy disconnect with that vendor/array. Sincerely, Randy Jennings