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Mon, 26 Aug 2024 06:49:10 -0700 (PDT) MIME-Version: 1.0 References: <20240826085347.1152675-1-mhocko@kernel.org> <20240826085347.1152675-3-mhocko@kernel.org> In-Reply-To: <20240826085347.1152675-3-mhocko@kernel.org> From: Yafang Shao Date: Mon, 26 Aug 2024 21:48:34 +0800 Message-ID: Subject: Re: [PATCH 2/2] mm: drop PF_MEMALLOC_NORECLAIM To: Michal Hocko 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, Michal Hocko Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: qkja7wtigawxwwotxzzkwcwhmsh8kqfr X-Rspam-User: X-Rspamd-Queue-Id: 5ED53C0017 X-Rspamd-Server: rspam02 X-HE-Tag: 1724680151-666102 X-HE-Meta: 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 q8zl1m7i XltKRwswrWbLtIatZ39Ct+NbERmEv+nNjbNKLMMdLJdclAHZ+kAM+luUTTaitRGGS/8GPUwNoiYAUn7dTaM+WBz479wq9rvaQiDVo01KDPc9T8siKwEHpQASOkmt3sAjkwR8o2aBeEEXxS0LWFviH4Eg9KW37ChssZFWJ0uMx7n5NpHyZIG16wbJFHi228WI0PO4UdGISaUe8lmVO9lfdiMgiP0u/j5BlDU22fbC8aRGJMvQtBD5KASv5cJwKt2Joi4BbDJYtzTbLo1Jhkcc4JIpXHQPKLlhv9amVcu2olQSFxmwe25PUeWo0UxrXaP7bIhqlpPEXJ6oA9P5EdeAkwC8qVvfIBiXEM67swfP50I1xuo9jQYMTPK4sK3XmqpqtY0Xu3WwQLftqKOw+6+tZJno1dTn3cyILRMCMz6kpcn2DwCoQnAugwkihengZE0GEVXYdF+C0CJpeUjZTxpSGHu36cWjf4bvDw2CCYRwkbtBYEzI= 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 4:53=E2=80=AFPM Michal Hocko wr= ote: > > 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 pa= ges from some other bdi. */ > #define PF_KTHREAD 0x00200000 /* I am a kernel thread *= / > #define PF_RANDOMIZE 0x00400000 /* Randomize virtual addr= ess space */ > -#define PF_MEMALLOC_NORECLAIM 0x00800000 /* All allocation request= s will clear __GFP_DIRECT_RECLAIM */ To maintain consistency with the other unused bits, it would be better to define PF__HOLE__00800000 instead. -- Regards Yafang