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15.21.0245.012; Mon, 27 Jul 2026 11:08:45 +0000 Message-ID: <2e003306-e6cf-4b4e-a0cb-19beb1ea08d4@windriver.com> Date: Mon, 27 Jul 2026 19:08:38 +0800 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] netfs: fix writeback ENOMEM by using __GFP_NOFAIL for rolling buffer To: David Howells Cc: pc@manguebit.org, netfs@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, hch@infradead.org References: <20260724073044.3400217-1-yun.zhou@windriver.com> <974342.1785146612@warthog.procyon.org.uk> Content-Language: en-US From: "Zhou, Yun" In-Reply-To: <974342.1785146612@warthog.procyon.org.uk> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SI2PR02CA0015.apcprd02.prod.outlook.com (2603:1096:4:194::16) To CH0PR11MB5332.namprd11.prod.outlook.com (2603:10b6:610:bf::17) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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18:03, David Howells wrote: > Yun Zhou wrote: > >> rolling_buffer_init() uses plain GFP_NOFS for its folio_queue allocation. >> In the writeback path this can fail and trigger WARN_ON_ONCE(folio != NULL) >> in netfs_writepages() when writeback_iter() returns additional dirty folios >> left unhandled. >> >> Writeback must not fail with -ENOMEM. Fix this by adding a gfp_t parameter >> to rolling_buffer_init() and passing GFP_NOFS | __GFP_NOFAIL from the >> writeback path, ensuring the allocation always succeeds. Read paths >> continue to use plain GFP_NOFS. > > I don't think this is the correct solution. I think you're right that a gfp_t > needs to be passed into rolling_buffer*(), but I think we need a mempool as > well. > > I have most of the patch for that, but I think I need adjust things so that > the read path uses GFP_KERNEL, not GFP_NOFS. > Got it. Your mempool approach looks good. Please let me know if you need anything from me. BR, Yun