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From: Kent Overstreet To: Matthew Wilcox Cc: Michal Hocko , Andrew Morton , Christoph Hellwig , Yafang Shao , jack@suse.cz, Christian Brauner , Alexander Viro , Paul Moore , James Morris , "Serge E. Hallyn" , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-bcachefs@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, Michal Hocko Subject: Re: [PATCH 1/2] bcachefs: do not use PF_MEMALLOC_NORECLAIM Message-ID: <3rfzqzmzzq5lvti3wndvctwi46ovntwume3h6nlvyfkym7b2md@is7sdli3ucaa> References: <20240826085347.1152675-1-mhocko@kernel.org> <20240826085347.1152675-2-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Stat-Signature: aepu1hmscbd6rt577xyet31b36eh8myh X-Rspamd-Queue-Id: 6D5A914001B X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1724701462-707353 X-HE-Meta: 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 kvZzVmVy lxYUMfUcY/i8YfBEiqeWDxETrOVQKWSkwmTG/zIgbYLYi4y0MGZNwk2U3kS/Xk5bnc4rM99cxVoubLsQTwRbXVC52mYzJiZmxbCdBzckO5XBJIa8JX4gJ2IwFgNMwtgF1o1LrcEvbkLpMAldoPCSbkcEe/mpDM64vEIYK7236EDNTRAD6ZPoKUifTvYe0dTcmnlgBku5nokooT2KXOl7Q6F94yfMPZZuJcMd4Xc54cMz5CukF3S1RzmtT3w== 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 Mon, Aug 26, 2024 at 08:41:42PM GMT, Matthew Wilcox wrote: > On Mon, Aug 26, 2024 at 03:39:47PM -0400, Kent Overstreet wrote: > > Given the amount of plumbing required here, it's clear that passing gfp > > flags is the less safe way of doing it, and this really does belong in > > the allocation context. > > > > Failure to pass gfp flags correctly (which we know is something that > > happens today, e.g. vmalloc -> pte allocation) means you're introducing > > a deadlock. > > The problem with vmalloc is that the page table allocation _doesn't_ > take a GFP parameter. and given the increasing usage of kvmalloc() this is something we really should be thinking about