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AJvYcCUzIdkPExBfv8Uz2VxhixyXQ2iwmwhsz9kTida/+ecUq07c2VOLrdqbpve9QlTznc2C7XVX1BaGOJEmyi5qDI8+H+4= X-Gm-Message-State: AOJu0YyR6E0nwStpKVqmJYJYDKIPDDfMlovyz+ocCqkHqagJ8npui+IR TikryXS3PvUwMSBs7g1H01OCIYKlDWXlwbdgVBG48mN7G3Nu7RmGm5i67O0MIs5jcnwYp98TYwi 9bTKOwGPTXZtDt36bF3hzf93H89g= X-Google-Smtp-Source: AGHT+IHRZrGX87cuGJRiUHttBtwhs8p+UCodXELlCDBbkFapXCMyAly9V29tY8JwT210q4nacgpgx2nFxvBIhZrCkVE= X-Received: by 2002:a05:6358:12a6:b0:1aa:d6fe:f424 with SMTP id e5c5f4694b2df-1b19d2ceac7mr295616955d.13.1723515000263; Mon, 12 Aug 2024 19:10:00 -0700 (PDT) MIME-Version: 1.0 References: <20240812090525.80299-1-laoar.shao@gmail.com> <20240812090525.80299-2-laoar.shao@gmail.com> In-Reply-To: From: Yafang Shao Date: Tue, 13 Aug 2024 10:09:24 +0800 Message-ID: Subject: Re: [PATCH 1/2] mm: Add memalloc_nowait_{save,restore} To: Christoph Hellwig Cc: akpm@linux-foundation.org, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, david@fromorbit.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Kent Overstreet Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: 8152FC0006 X-Rspamd-Server: rspam01 X-Stat-Signature: kme86p3zosjn4jypnzkuce18f5d8ui4o X-HE-Tag: 1723515001-295198 X-HE-Meta: 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 muHJy3/N u3v1SMgANRO2AgPV5h+fjndhwtKgpt2WMaVI8fz3BNpFssJuHVVgmVQ65d527uxNtvaFq8UefzS2L8dhZnpLtBYV/5jPz5T+YkLSLQsZSgyt/ljO2F142HGXGLjPQH8K4zhveYYNxXNSTxHolgDkfNghyeAgnsT+EJbBTh+N8Iz14hX7Mm5zvtSAxKS+UPquqd4peQKqgfwqIvTfSkY1cnCJdu76QUW0cE2baVprnL/V5QLz54ZhnHWQ3LASC2MHYML85ztfJDvU0eQQ1GuXl7NpuqEJEJUuPajvPOiofSXXJKZIvFeSlTB8412IOKQmCjmvJ3X6VDtk0hRqq83j+sEu38Itn9k4IQS8xbkXpSaoXMffPUCQSwV06cPFibf0rayyE05GK226X2UTtlFHSZS2NIiooYmzDJB0h0w3ZNb05sQFxFVn1NJoKlg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.166968, 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 12, 2024 at 9:21=E2=80=AFPM Christoph Hellwig wrote: > > On Mon, Aug 12, 2024 at 08:59:53PM +0800, Yafang Shao wrote: > > > > I don=E2=80=99t see any incompatibility in __alloc_pages_slowpath(). Th= e > > ~__GFP_DIRECT_RECLAIM flag only ensures that direct reclaim is not > > performed, but it doesn=E2=80=99t prevent the allocation of pages from > > ALLOC_MIN_RESERVE, correct? > > > > > and thus will lead to kernel crashes. > > > > Could you please explain in detail where this might lead to kernel cras= hes? > > Sorry, I misread your patch as doing what your subject says. > A nestable noreclaim is probably fine, but please name it that way, > as memalloc_nowait_{save,restore} implies a context version > of GFP_NOWAIT. There are already memalloc_noreclaim_{save,restore} which imply __GFP_MEMAL= LOC: memalloc_noreclaim_save - Marks implicit __GFP_MEMALLOC scope. That is why I name it memalloc_nowait_{save,restore}. GFP_NOWAIT has the same meaning with ~__GFP_DIRECT_RECLAIM: %GFP_NOWAIT is for kernel allocations that should not stall for direct reclaim, start physical IO or use any filesystem callback. --=20 Regards Yafang