linux-kernel - Re: [PATCH 07/11] vfs: add nowait parameter for file

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Message-ID: <20230904-trennen-gewettert-0b2dc5ba60bc@brauner>
Date:   Mon, 4 Sep 2023 11:51:40 +0200
From:   Christian Brauner <brauner@...nel.org>
To:     Hao Xu <hao.xu@...ux.dev>
Cc:     io-uring@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        Dominique Martinet <asmadeus@...ewreck.org>,
        Pavel Begunkov <asml.silence@...il.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Stefan Roesch <shr@...com>, Clay Harris <bugs@...ycon.org>,
        Dave Chinner <david@...morbit.com>,
        "Darrick J . Wong" <djwong@...nel.org>,
        linux-fsdevel@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-cachefs@...hat.com,
        ecryptfs@...r.kernel.org, linux-nfs@...r.kernel.org,
        linux-unionfs@...r.kernel.org, bpf@...r.kernel.org,
        netdev@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-btrfs@...r.kernel.org, codalist@...a.cs.cmu.edu,
        linux-f2fs-devel@...ts.sourceforge.net, cluster-devel@...hat.com,
        linux-mm@...ck.org, linux-nilfs@...r.kernel.org,
        devel@...ts.orangefs.org, linux-cifs@...r.kernel.org,
        samba-technical@...ts.samba.org, linux-mtd@...ts.infradead.org,
        Wanpeng Li <wanpengli@...cent.com>
Subject: Re: [PATCH 07/11] vfs: add nowait parameter for file_accessed()

On Sun, Aug 27, 2023 at 09:28:31PM +0800, Hao Xu wrote:
> From: Hao Xu <howeyxu@...cent.com>
> 
> Add a boolean parameter for file_accessed() to support nowait semantics.
> Currently it is true only with io_uring as its initial caller.
> 
> Signed-off-by: Hao Xu <howeyxu@...cent.com>
> ---
>  arch/s390/hypfs/inode.c | 2 +-
>  block/fops.c            | 2 +-
>  fs/btrfs/file.c         | 2 +-
>  fs/btrfs/inode.c        | 2 +-
>  fs/coda/dir.c           | 4 ++--
>  fs/ext2/file.c          | 4 ++--
>  fs/ext4/file.c          | 6 +++---
>  fs/f2fs/file.c          | 4 ++--
>  fs/fuse/dax.c           | 2 +-
>  fs/fuse/file.c          | 4 ++--
>  fs/gfs2/file.c          | 2 +-
>  fs/hugetlbfs/inode.c    | 2 +-
>  fs/nilfs2/file.c        | 2 +-
>  fs/orangefs/file.c      | 2 +-
>  fs/orangefs/inode.c     | 2 +-
>  fs/pipe.c               | 2 +-
>  fs/ramfs/file-nommu.c   | 2 +-
>  fs/readdir.c            | 2 +-
>  fs/smb/client/cifsfs.c  | 2 +-
>  fs/splice.c             | 2 +-
>  fs/ubifs/file.c         | 2 +-
>  fs/udf/file.c           | 2 +-
>  fs/xfs/xfs_file.c       | 6 +++---
>  fs/zonefs/file.c        | 4 ++--
>  include/linux/fs.h      | 5 +++--
>  mm/filemap.c            | 8 ++++----
>  mm/shmem.c              | 6 +++---
>  27 files changed, 43 insertions(+), 42 deletions(-)
> 
> diff --git a/arch/s390/hypfs/inode.c b/arch/s390/hypfs/inode.c
> index ee919bfc8186..55f562027c4f 100644
> --- a/arch/s390/hypfs/inode.c
> +++ b/arch/s390/hypfs/inode.c
> @@ -157,7 +157,7 @@ static ssize_t hypfs_read_iter(struct kiocb *iocb, struct iov_iter *to)
>  	if (!count)
>  		return -EFAULT;
>  	iocb->ki_pos = pos + count;
> -	file_accessed(file);
> +	file_accessed(file, false);

Why? If all you do is skip atime update anyway then just add something
like:

bool file_needs_atime(struct file *file)
{
       return !(file->f_flags & O_NOATIME) &&
              atime_needs_update(&file->f_path, d_inode(path->dentry));
}

and then

if (file_needs_atime(file) && IOURING_WANTS_ASYNC)
	return -EAGAIN;

instead of touching all this code.