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Wed, 27 Aug 2025 10:45:02 -0700 (PDT) MIME-Version: 1.0 References: <20250822192023.13477-1-ryncsn@gmail.com> <20250822192023.13477-5-ryncsn@gmail.com> In-Reply-To: From: Chris Li Date: Wed, 27 Aug 2025 10:44:50 -0700 X-Gmail-Original-Message-ID: X-Gm-Features: Ac12FXxitBgRzLWlNc1poHTuU4JtqvULJx8hBNZ7d5PhlQeGIAkFrGOgwUutM1U Message-ID: Subject: Re: [PATCH 4/9] mm, swap: tidy up swap device and cluster info helpers To: Baoquan He Cc: Kairui Song , linux-mm@kvack.org, Andrew Morton , Matthew Wilcox , Hugh Dickins , Barry Song , Nhat Pham , Kemeng Shi , Baolin Wang , Ying Huang , Johannes Weiner , David Hildenbrand , Yosry Ahmed , Lorenzo Stoakes , Zi Yan , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: hhmm4j56qtqui7pxzujfc43xq8yejzqs X-Rspam-User: X-Rspamd-Queue-Id: AF3DB180006 X-Rspamd-Server: rspam05 X-HE-Tag: 1756316704-472847 X-HE-Meta: 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 1R8Mno8g t5/WrsLGkIsbQMy+CfqKgJH+hGgfE0/gfteZLQN55vOhM36BTtpaTvI149TGRMceaJrpUzjM03ubHArXJmJW93eG0WomsjIdDex+syU8tvqhLo4lmG0SxT5ymZ6aVXXF4lIgWbl3sGWTgrxqY9hmMquZDmYuvZa5ZUTi/YHWXXgvGEF6d6PA6pcHnxhZMMhJHfITcDZM9yT66F429zt1fK2zk76vJenzP5FcwMY1AsDuc1bPSquWwNlzPLfvEpPhZXNVtUkxi6iClHa9AF9jaMVjEQNhm7HOQvZpP4AsC7N4KNrjWsixsxPuiaA== 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 Tue, Aug 26, 2025 at 8:47=E2=80=AFPM Baoquan He wrote: > > On 08/23/25 at 03:20am, Kairui Song wrote: > ...... > > diff --git a/mm/swap.h b/mm/swap.h > > index 223b40f2d37e..7b3efaa51624 100644 > > --- a/mm/swap.h > > +++ b/mm/swap.h > > @@ -15,6 +15,8 @@ extern int page_cluster; > > #define swap_entry_order(order) 0 > > #endif > > > > +extern struct swap_info_struct *swap_info[]; > > + > > /* > > * We use this to track usage of a cluster. A cluster is a block of sw= ap disk > > * space with SWAPFILE_CLUSTER pages long and naturally aligns in disk= . All > > @@ -53,9 +55,28 @@ enum swap_cluster_flags { > > #include /* for swp_offset */ > > #include /* for bio_end_io_t */ > > > > +/* > > + * Callers of all swp_* helpers here must ensure the entry is valid, a= nd > > + * pin the swap device by reference or in other ways. > > + */ > > +static inline struct swap_info_struct *swp_type_info(int type) > > +{ > > + struct swap_info_struct *si; > > + > > + si =3D READ_ONCE(swap_info[type]); /* rcu_dereference() */ > > + VM_WARN_ON_ONCE(percpu_ref_is_zero(&si->users)); /* race with swa= poff */ > > + return si; > > +} > > + > > +static inline struct swap_info_struct *swp_info(swp_entry_t entry) > > +{ > > + return swp_type_info(swp_type(entry)); > > +} > > swp_type_info() is only used by swp_info() in the whole series, can we > open code it in swp_info()? BTW, off topic here. I really don't like the "_info" suffix. Anything you can put into a C struct by definition is some kind of information. Same to the _struct. Anything defined by a struct is a struct. Don't need to say that. The "struct swap_info_struct" gets two of the unnecessary words. It should be something like "struct swap_file" or "struct swap_device". Renaming it is too invasive to the code base and it will mess up the git annotation history. Oh well. Chris