linux-kernel - Re: [PATCH 3/5] fuse: add FOPEN_INVAL

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Date:   Wed, 23 Aug 2023 11:01:42 +0200
From:   Miklos Szeredi <miklos@...redi.hu>
To:     Jiachen Zhang <zhangjiachen.jaycee@...edance.com>
Cc:     Jonathan Corbet <corbet@....net>, linux-fsdevel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        me@...x.top
Subject: Re: [PATCH 3/5] fuse: add FOPEN_INVAL_ATTR

On Tue, 11 Jul 2023 at 06:36, Jiachen Zhang
<zhangjiachen.jaycee@...edance.com> wrote:
>
> Add FOPEN_INVAL_ATTR so that the fuse daemon can ask kernel to invalidate
> the attr cache on file open.
>
> The fi->attr_version should be increased when handling FOPEN_INVAL_ATTR.
> Because if a FUSE request returning attributes (getattr, setattr, lookup,
> and readdirplus) starts before a FUSE_OPEN replying FOPEN_INVAL_ATTR, but
> finishes after the FUSE_OPEN, staled attributes will be set to the inode
> and falsely clears the inval_mask.
>
> Signed-off-by: Jiachen Zhang <zhangjiachen.jaycee@...edance.com>
> ---
>  fs/fuse/file.c            | 10 ++++++++++
>  include/uapi/linux/fuse.h |  2 ++
>  2 files changed, 12 insertions(+)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index de37a3a06a71..412824a11b7b 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -215,6 +215,16 @@ void fuse_finish_open(struct inode *inode, struct file *file)
>                 file_update_time(file);
>                 fuse_invalidate_attr_mask(inode, FUSE_STATX_MODSIZE);
>         }
> +
> +       if (ff->open_flags & FOPEN_INVAL_ATTR) {
> +               struct fuse_inode *fi = get_fuse_inode(inode);
> +
> +               spin_lock(&fi->lock);
> +               fi->attr_version = atomic64_inc_return(&fc->attr_version);

No need to add locking or change fi->attr_version.  This will be done
next time the attributes are updated.

Thanks,
Miklos