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[209.85.208.54]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a9392f5417csm121342966b.74.2024.09.24.12.24.31 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 24 Sep 2024 12:24:31 -0700 (PDT) Received: by mail-ed1-f54.google.com with SMTP id 4fb4d7f45d1cf-5c718af3354so1159116a12.0 for ; Tue, 24 Sep 2024 12:24:31 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCXLv5jijTxjX78pRwOAdgSrQ3WAoNYw8WhCMzuzpZ9xshwh1o6Xx3XVcPtOtvqntKX4+j2QDGCxWw==@kvack.org X-Received: by 2002:a17:907:9726:b0:a86:799d:f8d1 with SMTP id a640c23a62f3a-a93a06333edmr32505866b.47.1727205871314; Tue, 24 Sep 2024 12:24:31 -0700 (PDT) MIME-Version: 1.0 References: <52d45d22-e108-400e-a63f-f50ef1a0ae1a@meta.com> <5bee194c-9cd3-47e7-919b-9f352441f855@kernel.dk> <459beb1c-defd-4836-952c-589203b7005c@meta.com> <8697e349-d22f-43a0-8469-beb857eb44a1@kernel.dk> <0a3b09db-23e8-4a06-85f8-a0d7bbc3228b@meta.com> <15f15df9-ec90-486a-a784-effb8b2cb292@meta.com> In-Reply-To: <15f15df9-ec90-486a-a784-effb8b2cb292@meta.com> From: Linus Torvalds Date: Tue, 24 Sep 2024 12:24:14 -0700 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: Chris Mason Cc: Matthew Wilcox , Jens Axboe , Dave Chinner , 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" X-Rspam-User: X-Stat-Signature: 61xb7g7uxsaoi9r9n5aemjs9sj1w31oe X-Rspamd-Queue-Id: D2609180002 X-Rspamd-Server: rspam11 X-HE-Tag: 1727205874-932239 X-HE-Meta: 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 ayPTwex+ 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.001824, 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 Tue, 24 Sept 2024 at 12:18, Chris Mason wrote: > > A few days of load later and some extra printks, it turns out that > taking the writer lock in __filemap_add_folio() makes us dramatically > more likely to just return EEXIST than go into the xas_split_alloc() dance. .. and that sounds like a good thing, except for the test coverage, I guess. Which you seem to have fixed: > With the changes in 6.10, we only get into that xas_destroy() case above > when the conflicting entry is a shadow entry, so I changed my repro to > use memory pressure instead of fadvise. > > I also added a schedule_timeout(1) after the split alloc, and with all > of that I'm able to consistently make the xas_destroy() case trigger > without causing any system instability. Kairui Song's patches do seem > to have fixed things nicely. Linus