Re: [PATCH v5 11/18] fanotify: add a helper to check for pre content events

[Amir Goldstein <amir73il@gmail.com>]

On Wed, Sep 4, 2024 at 10:29 PM Josef Bacik <josef@toxicpanda.com> wrote:
>
> We want to emit events during page fault, and calling into fanotify
> could be expensive, so add a helper to allow us to skip calling into
> fanotify from page fault.  This will also be used to disable readahead
> for content watched files which will be handled in a subsequent patch.
>
> Reviewed-by: Christian Brauner <brauner@kernel.org>
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>

Reviewed-by: Amir Goldstein <amir73il@gmail.com>

Thanks,
Amir.

> ---
>  fs/notify/fsnotify.c             | 15 +++++++++++++++
>  include/linux/fsnotify_backend.h | 14 ++++++++++++++
>  2 files changed, 29 insertions(+)
>
> diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
> index 1ca4a8da7f29..30badf8ba36c 100644
> --- a/fs/notify/fsnotify.c
> +++ b/fs/notify/fsnotify.c
> @@ -201,6 +201,21 @@ static inline bool fsnotify_object_watched(struct inode *inode, __u32 mnt_mask,
>         return mask & marks_mask & ALL_FSNOTIFY_EVENTS;
>  }
>
> +#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
> +bool fsnotify_file_has_pre_content_watches(struct file *file)
> +{
> +       struct inode *inode = file_inode(file);
> +       __u32 mnt_mask = real_mount(file->f_path.mnt)->mnt_fsnotify_mask;
> +
> +       if (!(inode->i_sb->s_type->fs_flags & FS_ALLOW_HSM))
> +               return false;
> +
> +       return fsnotify_object_watched(inode, mnt_mask,
> +                                      FSNOTIFY_PRE_CONTENT_EVENTS);
> +}
> +#endif
> +
> +
>  /*
>   * Notify this dentry's parent about a child's events with child name info
>   * if parent is watching or if inode/sb/mount are interested in events with
> diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
> index 276320846bfd..b495a0676dd3 100644
> --- a/include/linux/fsnotify_backend.h
> +++ b/include/linux/fsnotify_backend.h
> @@ -900,6 +900,15 @@ static inline void fsnotify_init_event(struct fsnotify_event *event)
>         INIT_LIST_HEAD(&event->list);
>  }
>
> +#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
> +bool fsnotify_file_has_pre_content_watches(struct file *file);
> +#else
> +static inline bool fsnotify_file_has_pre_content_watches(struct file *file)
> +{
> +       return false;
> +}
> +#endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
> +
>  #else
>
>  static inline int fsnotify(__u32 mask, const void *data, int data_type,
> @@ -938,6 +947,11 @@ static inline u32 fsnotify_get_cookie(void)
>  static inline void fsnotify_unmount_inodes(struct super_block *sb)
>  {}
>
> +static inline bool fsnotify_file_has_pre_content_watches(struct file *file)
> +{
> +       return false;
> +}
> +
>  #endif /* CONFIG_FSNOTIFY */
>
>  #endif /* __KERNEL __ */
> --
> 2.43.0
>