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b=u1TlpRqL78dZgPhrTAw5P+r9y6/4V6xBYVNNv9k0Rl1NGpihej4QO7wtZqt4BklL0 z0ynv2MCb7D0DLfXz5/AHoAT8M+QWZMDrO0lELqXTB6R8WDaH4+h7ouYjw+vArgkge pah1TG1ondChQkaJY88ARyFz1udcI0vIfXT9Nd/4= Date: Tue, 25 Jun 2024 11:37:20 -0700 From: Andrew Morton To: Gavin Shan Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, david@redhat.com, djwong@kernel.org, willy@infradead.org, hughd@google.com, torvalds@linux-foundation.org, zhenyzha@redhat.com, shan.gavin@gmail.com Subject: Re: [PATCH 0/4] mm/filemap: Limit page cache size to that supported by xarray Message-Id: <20240625113720.a2fa982b5cb220b1068e5177@linux-foundation.org> In-Reply-To: <20240625090646.1194644-1-gshan@redhat.com> References: <20240625090646.1194644-1-gshan@redhat.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 877E680014 X-Stat-Signature: rygu1p7gzf9so76zk9nd6b1oe9hjjoyx X-HE-Tag: 1719340642-281695 X-HE-Meta: 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 103kmjYW 2TPQu37TAlWAZNtWzZ3WgDnXQcQeU7D//C7hK3cnRprQ101/WHOG9+dAycjrmRYdULpaLL4XRPGWa1WEZ1pqU7yjRNjRx7LDF2MqRjVDY6DuMMJZmlQ45FkORSD1p4psY9wJ5+jZnXRPVv7giQ7axAj23sgPIPwNg/QRsO04dPzz9PwML+KP14RQ+v6oi02KA57P+S2ajZLvFEbJVf4hwRSTSMCGkvIDcM0rgztYxhN2ucR+B40CVpkgVyE8/bc2PsF0NXkTaMkmNdaDctinI/+ulqOSkhl+jgnbe/oC5rsJcKUByi99QMoSYHKnkXnNM6Mdm5wSFsDlBX11fDRmfznulVVPvm/42b9mhPaOq5kCCpngAzyjIt7FcyFnMgFPafxujVoKX49dKcORF9RlOVcVkdcxYrcusOVbxYQRLaGWg8bE= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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, 25 Jun 2024 19:06:42 +1000 Gavin Shan wrote: > Currently, xarray can't support arbitrary page cache size. More details > can be found from the WARN_ON() statement in xas_split_alloc(). In our > test whose code is attached below, we hit the WARN_ON() on ARM64 system > where the base page size is 64KB and huge page size is 512MB. The issue > was reported long time ago and some discussions on it can be found here > [1]. > > [1] https://www.spinics.net/lists/linux-xfs/msg75404.html > > In order to fix the issue, we need to adjust MAX_PAGECACHE_ORDER to one > supported by xarray and avoid PMD-sized page cache if needed. The code > changes are suggested by David Hildenbrand. > > PATCH[1] adjusts MAX_PAGECACHE_ORDER to that supported by xarray > PATCH[2-3] avoids PMD-sized page cache in the synchronous readahead path > PATCH[4] avoids PMD-sized page cache for shmem files if needed Questions on the timing of these. 1&2 are cc:stable whereas 3&4 are not. I could split them and feed 1&2 into 6.10-rcX and 3&4 into 6.11-rc1. A problem with this approach is that we're putting a basically untested combination into -stable: 1&2 might have bugs which were accidentally fixed in 3&4. A way to avoid this is to add cc:stable to all four patches. What are your thoughts on this matter?