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AJvYcCVQwjO5z1P6VYy/pfYA/mAdOSeDjigHo75wdADR1h6pJNLkl0Txbb8n/dxZ27974OChs3njDWCVxQ==@kvack.org X-Gm-Message-State: AOJu0YxsoNn6QZDbqc1ZdJGiDGGvqopHMaLCwrQerpX2S2JeUouvpUAA VrMLZxyMLbTAixXh3ISoTNMsbOb6RPKSouYjGpEL5iBCTRYxx7ZsoMVH/rdw9ppRewBHhfQRg4g zMJef2xTJ2uD2Gi1UVH5B+yBv/TI= X-Google-Smtp-Source: AGHT+IH2RmcVes3AG0lbD9cuLYYXUcOiGnvmOTFEevBeg1h1Hv39lcvK78H5/4/K7h3wGT7+BQnzD/ccTxeDJ13johg= X-Received: by 2002:a05:6359:100c:b0:1c3:d56f:75d5 with SMTP id e5c5f4694b2df-1c6cd0a3e56mr285100855d.12.1731699199614; Fri, 15 Nov 2024 11:33:19 -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: Fri, 15 Nov 2024 11:33:08 -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-Rspam-User: X-Rspamd-Queue-Id: DC693C0028 X-Rspamd-Server: rspam01 X-Stat-Signature: mjc7or7xk8tkzhksfcow63aha43p3c7e X-HE-Tag: 1731699143-805779 X-HE-Meta: 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 59gkNI/H KYPluuORm+eJhJUvK6xyZpNL7QeAGEdM2XWOXbEX3dPIg5JE3zSgzayYolKth/szpVWGg2gYm10Hm/W5Hwz1c8qlW8ao4pOYFFVsAkC9AagxdnbVuysTYQsmrsnohuNGttlRodbMeqaOfPk7ovQettiWGc9wvJp/TTkYik1bQZptsLzYFR4OK9ERtJN3Bqnjh3tvsSK9pJsE0AR4SqtI7EdfsYoqdfp/t+Maz1YwdgeNXuwXaamZhjKdZyCEJBt7njy4FQeTMLVz1vl/z3drX4c7rO0IYKA6k4N5CwYU3CkJKo9Yh30e3B1/xRK0LZFbNCPRwyysw2DjTp0HemYunEnXdZOj+GcaPXk86Tb/CDAYHedK0wXM7dAKZBYvspKVsrBsWE3lfyxd+UxA= 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, Nov 11, 2024 at 1:11=E2=80=AFPM Joanne Koong wrote: > > 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 s= et > > > to indicate that writeback operations may block or take an indetermin= ate > > > amount of time to complete. Extra caution should be taken when waitin= g > > > 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 mod= ifying > > > folio contents */ > > > AS_INACCESSIBLE =3D 8, /* Do not attempt direct R/W access t= o the mapping */ > > > + AS_WRITEBACK_MAY_BLOCK =3D 9, /* Use caution when waiting on wr= iteback */ > > > > 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. Thinking about this some more, I think AS_WRITEBACK_ASYNC would be a better name. (AS_WRITEBACK_BLOCKING might imply that the writeback ->writepages() operation itself is blocking). I'll make this change for v5. Thanks, Joanne > > 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 a= ddress_space *mapping) > > > return test_bit(AS_INACCESSIBLE, &mapping->flags); > > > } > > > > > > +static inline void mapping_set_writeback_may_block(struct address_sp= ace *mapping) > > > +{ > > > + set_bit(AS_WRITEBACK_MAY_BLOCK, &mapping->flags); > > > +} > > > + > > > +static inline bool mapping_writeback_may_block(struct address_space = *mapping) > > > +{ > > > + 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 > > >