Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:7 as permitted sender) client-ip=2620:137:e000::3:7;
MIME-Version: 1.0
References: <20230928110554.34758-1-jlayton@kernel.org> <20230928110554.34758-3-jlayton@kernel.org>
In-Reply-To: <20230928110554.34758-3-jlayton@kernel.org>
From:   Amir Goldstein <amir73il@gmail.com>
Date:   Thu, 28 Sep 2023 14:35:13 +0300
Message-ID: <CAOQ4uxjSrgGr+6UOs4ADGYCderpQ7hAaPjNmB1DExAPLQQsHSg@mail.gmail.com>
Subject: Re: [PATCH 87/87] fs: move i_blocks up a few places in struct inode
To:     Jeff Layton <jlayton@kernel.org>
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        Christian Brauner <brauner@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        David Sterba <dsterba@suse.cz>,
        "Theodore Ts'o" <tytso@mit.edu>,
        Eric Biederman <ebiederm@xmission.com>,
        Kees Cook <keescook@chromium.org>, Jeremy Kerr <jk@ozlabs.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Nicholas Piggin <npiggin@gmail.com>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Sven Schnelle <svens@linux.ibm.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        =?UTF-8?B?QXJ2ZSBIasO4bm5ldsOlZw==?= <arve@android.com>,
        Todd Kjos <tkjos@android.com>,
        Martijn Coenen <maco@android.com>,
        Joel Fernandes <joel@joelfernandes.org>,
        Carlos Llamas <cmllamas@google.com>,
        Suren Baghdasaryan <surenb@google.com>,
        Mattia Dongili <malattia@linux.it>,
        Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Leon Romanovsky <leon@kernel.org>,
        Brad Warrum <bwarrum@linux.ibm.com>,
        Ritu Agarwal <rituagar@linux.ibm.com>,
        Hans de Goede <hdegoede@redhat.com>,
        =?UTF-8?Q?Ilpo_J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>,
        Mark Gross <markgross@kernel.org>,
        Jiri Slaby <jirislaby@kernel.org>,
        Eric Van Hensbergen <ericvh@kernel.org>,
        Latchesar Ionkov <lucho@ionkov.net>,
        Dominique Martinet <asmadeus@codewreck.org>,
        Christian Schoenebeck <linux_oss@crudebyte.com>,
        David Sterba <dsterba@suse.com>,
        David Howells <dhowells@redhat.com>,
        Marc Dionne <marc.dionne@auristor.com>,
        Ian Kent <raven@themaw.net>,
        Luis de Bethencourt <luisbg@kernel.org>,
        Salah Triki <salah.triki@gmail.com>,
        "Tigran A. Aivazian" <aivazian.tigran@gmail.com>,
        Chris Mason <clm@fb.com>, Josef Bacik <josef@toxicpanda.com>,
        Xiubo Li <xiubli@redhat.com>,
        Ilya Dryomov <idryomov@gmail.com>,
        Jan Harkes <jaharkes@cs.cmu.edu>, coda@cs.cmu.edu,
        Joel Becker <jlbec@evilplan.org>,
        Christoph Hellwig <hch@lst.de>,
        Nicolas Pitre <nico@fluxnic.net>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Ard Biesheuvel <ardb@kernel.org>, Gao Xiang <xiang@kernel.org>,
        Chao Yu <chao@kernel.org>, Yue Hu <huyue2@coolpad.com>,
        Jeffle Xu <jefflexu@linux.alibaba.com>,
        Namjae Jeon <linkinjeon@kernel.org>,
        Sungjong Seo <sj1557.seo@samsung.com>,
        Jan Kara <jack@suse.com>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        Jaegeuk Kim <jaegeuk@kernel.org>,
        OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>,
        Christoph Hellwig <hch@infradead.org>,
        Miklos Szeredi <miklos@szeredi.hu>,
        Bob Peterson <rpeterso@redhat.com>,
        Andreas Gruenbacher <agruenba@redhat.com>,
        Richard Weinberger <richard@nod.at>,
        Anton Ivanov <anton.ivanov@cambridgegreys.com>,
        Johannes Berg <johannes@sipsolutions.net>,
        Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Muchun Song <muchun.song@linux.dev>, Jan Kara <jack@suse.cz>,
        David Woodhouse <dwmw2@infradead.org>,
        Dave Kleikamp <shaggy@kernel.org>, Tejun Heo <tj@kernel.org>,
        Trond Myklebust <trond.myklebust@hammerspace.com>,
        Anna Schumaker <anna@kernel.org>,
        Chuck Lever <chuck.lever@oracle.com>,
        Neil Brown <neilb@suse.de>,
        Olga Kornievskaia <kolga@netapp.com>,
        Dai Ngo <Dai.Ngo@oracle.com>, Tom Talpey <tom@talpey.com>,
        Ryusuke Konishi <konishi.ryusuke@gmail.com>,
        Anton Altaparmakov <anton@tuxera.com>,
        Konstantin Komarov <almaz.alexandrovich@paragon-software.com>,
        Mark Fasheh <mark@fasheh.com>,
        Joseph Qi <joseph.qi@linux.alibaba.com>,
        Bob Copeland <me@bobcopeland.com>,
        Mike Marshall <hubcap@omnibond.com>,
        Martin Brandenburg <martin@omnibond.com>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Iurii Zaikin <yzaikin@google.com>,
        Tony Luck <tony.luck@intel.com>,
        "Guilherme G. Piccoli" <gpiccoli@igalia.com>,
        Anders Larsen <al@alarsen.net>,
        Steve French <sfrench@samba.org>,
        Paulo Alcantara <pc@manguebit.com>,
        Ronnie Sahlberg <lsahlber@redhat.com>,
        Shyam Prasad N <sprasad@microsoft.com>,
        Sergey Senozhatsky <senozhatsky@chromium.org>,
        Phillip Lougher <phillip@squashfs.org.uk>,
        Steven Rostedt <rostedt@goodmis.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Evgeniy Dushistov <dushistov@mail.ru>,
        Chandan Babu R <chandan.babu@oracle.com>,
        "Darrick J. Wong" <djwong@kernel.org>,
        Damien Le Moal <dlemoal@kernel.org>,
        Naohiro Aota <naohiro.aota@wdc.com>,
        Johannes Thumshirn <jth@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>,
        Yonghong Song <yonghong.song@linux.dev>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
        Hugh Dickins <hughd@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        John Johansen <john.johansen@canonical.com>,
        Paul Moore <paul@paul-moore.com>,
        James Morris <jmorris@namei.org>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        Stephen Smalley <stephen.smalley.work@gmail.com>,
        Eric Paris <eparis@parisplace.org>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org,
        linux-s390@vger.kernel.org, platform-driver-x86@vger.kernel.org,
        linux-rdma@vger.kernel.org, linux-serial@vger.kernel.org,
        linux-usb@vger.kernel.org, v9fs@lists.linux.dev,
        linux-afs@lists.infradead.org, autofs@vger.kernel.org,
        linux-btrfs@vger.kernel.org, ceph-devel@vger.kernel.org,
        codalist@coda.cs.cmu.edu, linux-efi@vger.kernel.org,
        linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net, gfs2@lists.linux.dev,
        linux-um@lists.infradead.org, linux-mtd@lists.infradead.org,
        jfs-discussion@lists.sourceforge.net, linux-nfs@vger.kernel.org,
        linux-nilfs@vger.kernel.org, linux-ntfs-dev@lists.sourceforge.net,
        ntfs3@lists.linux.dev, ocfs2-devel@lists.linux.dev,
        linux-karma-devel@lists.sourceforge.net, devel@lists.orangefs.org,
        linux-unionfs@vger.kernel.org, linux-hardening@vger.kernel.org,
        reiserfs-devel@vger.kernel.org, linux-cifs@vger.kernel.org,
        samba-technical@lists.samba.org,
        linux-trace-kernel@vger.kernel.org, linux-xfs@vger.kernel.org,
        bpf@vger.kernel.org, netdev@vger.kernel.org,
        apparmor@lists.ubuntu.com, linux-security-module@vger.kernel.org,
        selinux@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Thu, Sep 28, 2023 at 2:06=E2=80=AFPM Jeff Layton <jlayton@kernel.org> wr=
ote:
>
> The recent change to use discrete integers instead of struct timespec64
> in struct inode shaved 8 bytes off of it, but it also moves the i_lock
> into the previous cacheline, away from the fields that it protects.
>
> Move i_blocks up above the i_lock, which moves the new 4 byte hole to
> just after the timestamps, without changing the size of the structure.
>

Instead of creating an implicit hole, can you please move i_generation
to fill the 4 bytes hole.

It makes sense in the same cache line with i_ino and I could
use the vacant 4 bytes hole above i_fsnotify_mask to expand the
mask to 64bit (the 32bit event mask space is running out).

Thanks,
Amir.

> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
>  include/linux/fs.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index de902ff2938b..3e0fe0f52e7c 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -677,11 +677,11 @@ struct inode {
>         u32                     i_atime_nsec;
>         u32                     i_mtime_nsec;
>         u32                     i_ctime_nsec;
> +       blkcnt_t                i_blocks;
>         spinlock_t              i_lock; /* i_blocks, i_bytes, maybe i_siz=
e */
>         unsigned short          i_bytes;
>         u8                      i_blkbits;
>         u8                      i_write_hint;
> -       blkcnt_t                i_blocks;
>
>  #ifdef __NEED_I_SIZE_ORDERED
>         seqcount_t              i_size_seqcount;
> --
> 2.41.0
>