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[209.85.167.47]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-2f79d2e1eb5sm14719341fa.27.2024.09.18.20.03.40 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 18 Sep 2024 20:03:41 -0700 (PDT) Received: by mail-lf1-f47.google.com with SMTP id 2adb3069b0e04-5365c060f47so390494e87.2 for ; Wed, 18 Sep 2024 20:03:40 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCU52sWp9O3+DqTo02lay7KcuwLWHF6zpZJkl8M+01GGaLUQW0PcUnvhkF5ZtZ6EmFSnOZRkZEfSAeNGzCYb@vger.kernel.org X-Received: by 2002:a05:6512:220d:b0:535:6a75:8ac8 with SMTP id 2adb3069b0e04-53678fc24e6mr13825268e87.23.1726715020071; Wed, 18 Sep 2024 20:03:40 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <74cceb67-2e71-455f-a4d4-6c5185ef775b@meta.com> <52d45d22-e108-400e-a63f-f50ef1a0ae1a@meta.com> <5bee194c-9cd3-47e7-919b-9f352441f855@kernel.dk> <459beb1c-defd-4836-952c-589203b7005c@meta.com> In-Reply-To: From: Linus Torvalds Date: Thu, 19 Sep 2024 05:03:23 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: Known and unfixed active data loss bug in MM + XFS with large folios since Dec 2021 (any kernel from 6.1 upwards) To: Dave Chinner Cc: Matthew Wilcox , Chris Mason , Jens Axboe , Christian Theune , linux-mm@kvack.org, "linux-xfs@vger.kernel.org" , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Daniel Dao , regressions@lists.linux.dev, regressions@leemhuis.info Content-Type: text/plain; charset="UTF-8" On Thu, 19 Sept 2024 at 03:43, Dave Chinner wrote: > > Should we be asking for 6758c1128ceb to be backported to all > stable kernels then? I think we should just do the simple one-liner of adding a "xas_reset()" to after doing xas_split_alloc() (or do it inside the xas_split_alloc()). That said, I do also think it would be really good if the 'xa_lock*()' family of functions also had something like a WARN_ON_ONCE(xas->xa_node && !xa_err(xas->xa_node)); which I think would have caught this. Because right now nothing at all checks "we dropped the xa lock, and held xas state over it". Linus