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AJvYcCWhdATLiRISRAfbatRH/xKL+HP7iAZh9s17giHUy5SKev4Ck3vyHbKXPhVAhF5eLnKtrS6Pa3j9nA==@kvack.org X-Gm-Message-State: AOJu0YysByBjAXgDbzphXVy2iC/YnEbOATp0cE2hIyD0cRD7JRPRZJP3 tANOrk5nA63gDc/zT9vJU9Hpkr0Pr4aBdUQIP1F1PIoZSYgInRBt+c7NaPLmpFN66Q50AhA9B2g 5tri7b5d6S7PfVVvMyfhbLLpH+WU= X-Google-Smtp-Source: AGHT+IGN9ZO/+N+r0n0P+Zj63FMITfOdmxQ/lqEoV5Fi5gl96VhVmitjdYWqxbhfMtAW0FfCDRlFyjDmoZ8Cbxt3Ixo= X-Received: by 2002:a05:622a:1990:b0:458:4bf1:1f46 with SMTP id d75a77b69052e-4630942ad76mr235936441cf.53.1731359505782; Mon, 11 Nov 2024 13:11:45 -0800 (PST) MIME-Version: 1.0 References: <20241107235614.3637221-1-joannelkoong@gmail.com> <20241107235614.3637221-2-joannelkoong@gmail.com> In-Reply-To: From: Joanne Koong Date: Mon, 11 Nov 2024 13:11:35 -0800 Message-ID: Subject: Re: [PATCH v4 1/6] mm: add AS_WRITEBACK_MAY_BLOCK mapping flag To: Shakeel Butt Cc: miklos@szeredi.hu, linux-fsdevel@vger.kernel.org, jefflexu@linux.alibaba.com, josef@toxicpanda.com, linux-mm@kvack.org, bernd.schubert@fastmail.fm, kernel-team@meta.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 35C4A1C000A X-Stat-Signature: pp6jorirown1ob37p6trb6ehne68ayat X-Rspam-User: X-HE-Tag: 1731359429-230605 X-HE-Meta: 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 T/DIlIlU xd+pGdNcQPrDsjksZojc6xpmA7/Wyqx8mQz7+eehSkBbPoBjivIO1uzDjRvuDGHbdIUYOgzf33bcsQqtZKZ21oVWOaLfQMcIBUKRWP2qQvMgye+PI31ueSsykCyQ4wnqM57JpsU0BLo22sdI134OazKx4x+Anl9V1X71OMEun3HnCen/RBZZHNzgWDCIMhSJjYgCEh3FEaOUuwK6zc548bp57ZGn0TyG+ddtFesVXUHQRl7WcqqVBew+3BBIFfVtzDpKLZ21+IYzw/J/Y7P5y/Vx5tex+GbjsMYhJWIQJwIxstJ91x9/O8C5dQxrcI41oIQdisHnFu7CgJPYF+XYliwmyOlGOf/+MjVTs6L8eRw6cjq5gLI6lhDb9foVJSNE4MJUekfwYUsCrbl4= 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 Fri, Nov 8, 2024 at 4:10=E2=80=AFPM Shakeel Butt wrote: > > On Thu, Nov 07, 2024 at 03:56:09PM -0800, Joanne Koong wrote: > > Add a new mapping flag AS_WRITEBACK_MAY_BLOCK which filesystems may set > > to indicate that writeback operations may block or take an indeterminat= e > > amount of time to complete. Extra caution should be taken when waiting > > on writeback for folios belonging to mappings where this flag is set. > > > > Signed-off-by: Joanne Koong > > --- > > include/linux/pagemap.h | 11 +++++++++++ > > 1 file changed, 11 insertions(+) > > > > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h > > index 68a5f1ff3301..eb5a7837e142 100644 > > --- a/include/linux/pagemap.h > > +++ b/include/linux/pagemap.h > > @@ -210,6 +210,7 @@ enum mapping_flags { > > AS_STABLE_WRITES =3D 7, /* must wait for writeback before modif= ying > > folio contents */ > > AS_INACCESSIBLE =3D 8, /* Do not attempt direct R/W access to = the mapping */ > > + AS_WRITEBACK_MAY_BLOCK =3D 9, /* Use caution when waiting on writ= eback */ > > To me 'may block' does not feel right. For example in reclaim code, > folio_wait_writeback() can get blocked and that is fine. However with > non-privileged fuse involved, there are security concerns. Somehow 'may > block' does not convey that. Anyways, I am not really pushing back but > I think there is a need for better name here. Ahh I see where this naming causes confusion - the "MAY_BLOCK" part could be interpreted in two ways: a) may block as in it's possible for the writeback to block and b) may block as in it's permissible/ok for the writeback to block. I intended "may block" to signify a) but you're right, it could be easily interpreted as b). I'll change this to AS_WRITEBACK_BLOCKING. Thanks, Joanne > > > /* Bits 16-25 are used for FOLIO_ORDER */ > > AS_FOLIO_ORDER_BITS =3D 5, > > AS_FOLIO_ORDER_MIN =3D 16, > > @@ -335,6 +336,16 @@ static inline bool mapping_inaccessible(struct add= ress_space *mapping) > > return test_bit(AS_INACCESSIBLE, &mapping->flags); > > } > > > > +static inline void mapping_set_writeback_may_block(struct address_spac= e *mapping) > > +{ > > + set_bit(AS_WRITEBACK_MAY_BLOCK, &mapping->flags); > > +} > > + > > +static inline bool mapping_writeback_may_block(struct address_space *m= apping) > > +{ > > + return test_bit(AS_WRITEBACK_MAY_BLOCK, &mapping->flags); > > +} > > + > > static inline gfp_t mapping_gfp_mask(struct address_space * mapping) > > { > > return mapping->gfp_mask; > > -- > > 2.43.5 > >