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b=Or5RWsezVdmJXmfKXLU/+RO6AW73b9HhH7qXdzh3PhUekUvVn6glLz/t2uLWGRfvF Bnqb7nfaVta9+E8dtOVG7lGniJp9Hwx3p6AnZwttYtQVYMBAAwQU8OiwzjBXdOphRW VZALKGp30KZ3cZqVQ3YRe7/+95QRXATjcCBJgGdUT23sZymEw1UlTGzysFv6oa1ZUg or4GK1TFMxuOsfIJdeThcNUTdzLNXZQf3sNf+wZMs0J+sOoo8zPsmVHKgbUq9XBoAS jdooTCWwai/K1tLXTdRFl3NlyHEtXQMoS8nSMi1Usc0hMx1zqPFMcvbqqHIEJ+ZYE0 SdIOAzd7JNnXQ== Received: by mail-qv1-f54.google.com with SMTP id 6a1803df08f44-89c43c4c383so71885446d6.1 for ; Tue, 31 Mar 2026 02:22:05 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCXbGJYohVs5eloe9or6sSpmE1zI8RISn142EXyNbn08hLn5GEkzIkT61hVjBHiO9W/drQSV+EAAqQ==@kvack.org X-Gm-Message-State: AOJu0YxeerlLFqkIMVR8+wKglrTnBM5XviSVoST1f/tUo/NJP4KkQQeh UiexaPybm5pmHDH4nSbWonJtfgBWJ6bpUoX1/99nlq6gaj2Fd1prY77UNpYIoJBGLYR11HnGktS RFnSqYBpCfFE2K27RM0ml4uBvkCLfQpM= X-Received: by 2002:ad4:5c8b:0:b0:89c:607c:8c4b with SMTP id 6a1803df08f44-89ce8d5d0d3mr214426876d6.5.1774948924079; Tue, 31 Mar 2026 02:22:04 -0700 (PDT) MIME-Version: 1.0 References: <20260328075812.11060-1-21cnbao@gmail.com> <20260328075812.11060-3-21cnbao@gmail.com> In-Reply-To: From: Barry Song Date: Tue, 31 Mar 2026 22:21:52 +1300 X-Gmail-Original-Message-ID: X-Gm-Features: AQROBzCJdjrXABR4qdV-glYAtPXEJJS9NfovzfViIj2lstem4gT-6tr0zCej8sY Message-ID: Subject: Re: [PATCH v2 2/3] mm/swap: use swap_ops to register swap device's methods To: Chris Li Cc: akpm@linux-foundation.org, linux-mm@kvack.org, bhe@redhat.com, kasong@tencent.com, nphamcs@gmail.com, shikemeng@huaweicloud.com, youngjun.park@lge.com, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: 3B1562000A X-Stat-Signature: km88bk8af7grziz8zp7ptz99gi7p17oe X-Rspamd-Server: rspam06 X-HE-Tag: 1774948926-16848 X-HE-Meta: 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 GjyGvuJT 1eQiO9MMzjw/U6NWNRttDBQafWihNBrVH7jkx94fMWFf/uiFoA4iRFSzFQNafIPdqz8sfalU6Ddr4qXRGS/EmURi5QLDmXpQxpOK/coEStkKQvRhEwXP4C+yO6t6OeFxIA/lPl4ZSSZ15xwdWuWmY+53gznknAlKgE8jcCc+37m0knXhOwkA1j9zcrvcYDvvIJnh6kCeXxsnp7KwM7fopUx4JvsIwbpV+4l9uR8+thH4hH3tJg2+nPz/dH595HPsrmSy7r7aU/wqMAtVsukOJ3dhbGiabeVKj4LlL0UoynrK1r8ng78GyTST44wF72Xf3EQZDtr3MNM25RbjiBKRqV0PvBJncstHI+/4CREoVYsbfBWvsTPwv9CpHAMjZO6o63Deci9WCpdgQZq2CBtYpshIqrQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Mar 31, 2026 at 4:31=E2=80=AFPM Chris Li wrote: > > On Sat, Mar 28, 2026 at 12:58=E2=80=AFAM Barry Song <21cnbao@gmail.com> w= rote: > > > > From: Baoquan He > > > > This simplifies codes and makes logic clearer. And also makes later any > > new swap device type being added easier to handle. > > > > Currently there are three types of swap devices: bdev_fs, bdev_sync > > and bdev_async, and only operations read_folio and write_folio are > > included. In the future, there could be more swap device types added > > and more appropriate opeations adapted into swap_ops. > > Should add that there is no functional change expected from this patch. Sounds good to me. [...] > > +static const struct swap_ops bdev_async_swap_ops =3D { > > + .read_folio =3D swap_read_folio_bdev_async, > > + .write_folio =3D swap_writepage_bdev_async, > > +}; > > + > > +void setup_swap_ops(struct swap_info_struct *sis) > > setup_swap_ops()` needs to return an indication of an error. > The error is that sis->ops is NULL or op->read_folio =3D=3D NULL or > op->write_folio =3D=3D NULL. > If there is an error, we should fail the swapon. Right now there is no possibility for any of the ops (read_folio or write_folio) to be NULL, so I was using VM_WARN_ON as an assertion to catch bugs in kernel code. That said, I agree we can return an error earlier instead of letting swapon fail later. I think it may still make sense to keep a VM_WARN_ON in setup_swap_ops() before returning -EINVAL or a similar error? Thanks Barry