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[49.179.0.65]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7143432ee26sm9279075b3a.188.2024.08.27.21.10.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Aug 2024 21:10:00 -0700 (PDT) Received: from dave by dread.disaster.area with local (Exim 4.96) (envelope-from ) id 1sjA0L-00FJwC-3A; Wed, 28 Aug 2024 14:09:58 +1000 Date: Wed, 28 Aug 2024 14:09:57 +1000 From: Dave Chinner To: Michal Hocko Cc: Andrew Morton , Christoph Hellwig , Yafang Shao , Kent Overstreet , 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 v2] bcachefs: do not use PF_MEMALLOC_NORECLAIM Message-ID: References: <20240826085347.1152675-2-mhocko@kernel.org> <20240827061543.1235703-1-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240827061543.1235703-1-mhocko@kernel.org> X-Stat-Signature: zsozmhbcgg1xmw37g7hazf1jq353n6nf X-Rspam-User: X-Rspamd-Queue-Id: 30BAD140004 X-Rspamd-Server: rspam02 X-HE-Tag: 1724818201-111463 X-HE-Meta: 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 r8gno9JU 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 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, Aug 27, 2024 at 08:15:43AM +0200, Michal Hocko wrote: > From: Michal Hocko > > bch2_new_inode relies on PF_MEMALLOC_NORECLAIM to try to allocate a new > inode to achieve GFP_NOWAIT semantic while holding locks. If this > allocation fails it will drop locks and use GFP_NOFS allocation context. > > We would like to drop PF_MEMALLOC_NORECLAIM because it is really > dangerous to use if the caller doesn't control the full call chain with > this flag set. E.g. if any of the function down the chain needed > GFP_NOFAIL request the PF_MEMALLOC_NORECLAIM would override this and > cause unexpected failure. > > While this is not the case in this particular case using the scoped gfp > semantic is not really needed bacause we can easily pus the allocation > context down the chain without too much clutter. > > Acked-by: Christoph Hellwig > Signed-off-by: Michal Hocko Looks good to me. Reviewed-by: Dave Chinner -- Dave Chinner david@fromorbit.com