linux-ext4 - Re: [PATCH 06/11] fsnotify: Support FS

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Date:   Fri, 21 May 2021 12:13:44 +0300
From:   Amir Goldstein <amir73il@...il.com>
To:     Gabriel Krisman Bertazi <krisman@...labora.com>
Cc:     kernel@...labora.com, "Darrick J . Wong" <djwong@...nel.org>,
        "Theodore Ts'o" <tytso@....edu>,
        Dave Chinner <david@...morbit.com>, Jan Kara <jack@...e.com>,
        David Howells <dhowells@...hat.com>,
        Khazhismel Kumykov <khazhy@...gle.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 06/11] fsnotify: Support FS_ERROR event type

On Fri, May 21, 2021 at 5:42 AM Gabriel Krisman Bertazi
<krisman@...labora.com> wrote:
>
> Expose a new type of fsnotify event for filesystems to report errors for
> userspace monitoring tools.  fanotify will send this type of
> notification for FAN_ERROR events.
>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
>
> ---
> Changes since v1:
>   - Overload FS_ERROR with FS_IN_IGNORED
> ---
>  include/linux/fsnotify_backend.h | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
> index 1ce66748a2d2..bbef2df3fbc7 100644
> --- a/include/linux/fsnotify_backend.h
> +++ b/include/linux/fsnotify_backend.h
> @@ -42,6 +42,12 @@
>
>  #define FS_UNMOUNT             0x00002000      /* inode on umount fs */
>  #define FS_Q_OVERFLOW          0x00004000      /* Event queued overflowed */
> +#define FS_ERROR               0x00008000      /* Filesystem Error (fanotify) */
> +
> +/*
> + * FS_IN_IGNORED overloads FS_ERROR.  It is only used internally by inotify
> + * which does not support FS_ERROR.
> + */
>  #define FS_IN_IGNORED          0x00008000      /* last inotify event here */
>
>  #define FS_OPEN_PERM           0x00010000      /* open event in an permission hook */
> @@ -95,7 +101,8 @@
>  #define ALL_FSNOTIFY_EVENTS (ALL_FSNOTIFY_DIRENT_EVENTS | \
>                              FS_EVENTS_POSS_ON_CHILD | \
>                              FS_DELETE_SELF | FS_MOVE_SELF | FS_DN_RENAME | \
> -                            FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED)
> +                            FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
> +                            FS_ERROR)
>
>  /* Extra flags that may be reported with event or control handling of events */
>  #define ALL_FSNOTIFY_FLAGS  (FS_EXCL_UNLINK | FS_ISDIR | FS_IN_ONESHOT | \
> @@ -248,6 +255,12 @@ enum fsnotify_data_type {
>         FSNOTIFY_EVENT_NONE,
>         FSNOTIFY_EVENT_PATH,
>         FSNOTIFY_EVENT_INODE,
> +       FSNOTIFY_EVENT_ERROR,
> +};
> +
> +struct fs_error_report {
> +       int error;
> +       struct inode *inode;
>  };
>
>  static inline struct inode *fsnotify_data_inode(const void *data, int data_type)

Your patch may not use it, but I prefer that fsnotify_data_inode() knows
how to handle FSNOTIFY_EVENT_ERROR type.

You will need it if you choose to implement my proposal of optional
FAN_EVENT_INFO_TYPE_FID record.

Thanks,
Amir.