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[109.81.92.122]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a868f2e66eesm687492566b.97.2024.08.26.09.54.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Aug 2024 09:54:03 -0700 (PDT) Date: Mon, 26 Aug 2024 18:54:02 +0200 From: Michal Hocko To: Yafang Shao Cc: Andrew Morton , Christoph Hellwig , 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 Subject: Re: [PATCH 2/2] mm: drop PF_MEMALLOC_NORECLAIM Message-ID: References: <20240826085347.1152675-1-mhocko@kernel.org> <20240826085347.1152675-3-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspam-User: X-Stat-Signature: h566pt395q65j15f37n6f1y19x1mtn7p X-Rspamd-Queue-Id: 42BC94000E X-Rspamd-Server: rspam11 X-HE-Tag: 1724691245-626086 X-HE-Meta: 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 FK2Of7er 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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 Mon 26-08-24 21:48:34, Yafang Shao wrote: > On Mon, Aug 26, 2024 at 4:53 PM Michal Hocko wrote: > > > > From: Michal Hocko > > > > There is no existing user of the flag and the flag is dangerous because > > a nested allocation context can use GFP_NOFAIL which could cause > > unexpected failure. Such a code would be hard to maintain because it > > could be deeper in the call chain. > > > > PF_MEMALLOC_NORECLAIM has been added even when it was pointed out [1] > > that such a allocation contex is inherently unsafe if the context > > doesn't fully control all allocations called from this context. > > > > [1] https://lore.kernel.org/all/ZcM0xtlKbAOFjv5n@tiehlicka/ > > > > Signed-off-by: Michal Hocko > > --- > > include/linux/sched.h | 1 - > > include/linux/sched/mm.h | 7 ++----- > > 2 files changed, 2 insertions(+), 6 deletions(-) > > > > diff --git a/include/linux/sched.h b/include/linux/sched.h > > index f8d150343d42..72dad3a6317a 100644 > > --- a/include/linux/sched.h > > +++ b/include/linux/sched.h > > @@ -1657,7 +1657,6 @@ extern struct pid *cad_pid; > > * I am cleaning dirty pages from some other bdi. */ > > #define PF_KTHREAD 0x00200000 /* I am a kernel thread */ > > #define PF_RANDOMIZE 0x00400000 /* Randomize virtual address space */ > > -#define PF_MEMALLOC_NORECLAIM 0x00800000 /* All allocation requests will clear __GFP_DIRECT_RECLAIM */ > > To maintain consistency with the other unused bits, it would be better > to define PF__HOLE__00800000 instead. OK -- Michal Hocko SUSE Labs