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[49.179.78.197]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-719918df7ccsm150940b3a.40.2024.09.18.18.43.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Sep 2024 18:43:17 -0700 (PDT) Received: from dave by dread.disaster.area with local (Exim 4.96) (envelope-from ) id 1sr6CR-0072c8-0x; Thu, 19 Sep 2024 11:43:15 +1000 Date: Thu, 19 Sep 2024 11:43:15 +1000 From: Dave Chinner To: Matthew Wilcox Cc: Chris Mason , Jens Axboe , Linus Torvalds , 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 Subject: Re: Known and unfixed active data loss bug in MM + XFS with large folios since Dec 2021 (any kernel from 6.1 upwards) Message-ID: 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: cnxe9f7xkjo94cd9mt7h7sk49tgpnien X-Rspamd-Queue-Id: CDB3E80012 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1726710199-374097 X-HE-Meta: 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 L3DsgI0V RVMeIp1RiIg9e/WW/ZwcA/MM+rjUqX2RZa5m46rs0X9dmgCufmFxWllpHOERbZp+tjxKw9Dilnp6p1l9IgTDc7ICGmMVWcRyFraUIFllMPXseJoMY/OiLQ/GmWKdEqrXPrj3tPufv0Rs10sYUNiYo7kpDKewAF1SB7mxTmdWYqGA9g+djOqosUUriwNKqAe5qzJHaYOX/YwwrYkOmvgg/NZ8IbbbsU6fi1t+viGLiCsJoyHnEyKI2+1AJ15sKGMOw/Ln0w1mS56TODxyFUolf/TpOhq+yGJcbtwoofVyFnO3EH1BMRujKeMuTBvfj8dRlN6Bg2Z82gdWI8DKpSZDmnLrw58gttMhp46mi8HWn+U9l7MTxQ/qeq/w3QE/hGn3PHfwOT10sv94ZdLt7f9QThBnHKOpjAJ2J2ePbfWLSDnysA7pLJBrSSkQVMEkKcMs8XnfwC1Xjn5Sxr8I= X-Bogosity: Ham, tests=bogofilter, spamicity=0.031457, 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 Wed, Sep 18, 2024 at 02:34:57PM +0100, Matthew Wilcox wrote: > On Wed, Sep 18, 2024 at 11:28:52AM +0200, Chris Mason wrote: > > I think the bug was in __filemap_add_folio()'s usage of xarray_split_alloc() > > and the tree changing before taking the lock. It's just a guess, but that > > was always my biggest suspect. > > Oh god, that's it. > > there should have been an xas_reset() after calling xas_split_alloc(). > > and 6758c1128ceb calls xas_reset() after calling xas_split_alloc(). Should we be asking for 6758c1128ceb to be backported to all stable kernels then? -Dave. -- Dave Chinner david@fromorbit.com