Re: [PATCH v6 10/21] fsnotify: Support FS_ERROR event type

[Amir Goldstein <amir73il@gmail.com>]

On Fri, Aug 13, 2021 at 12:41 AM Gabriel Krisman Bertazi
<krisman@collabora.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_FS_ERROR events.  This also introduce a helper for
> generating the new event.
>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>

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

>
> ---
> Changes since v5:
>   - pass sb inside data field (jan)
> Changes since v3:
>   - Squash patch ("fsnotify: Introduce helpers to send error_events")
>   - Drop reviewed-bys!
>
> Changes since v2:
>   - FAN_ERROR->FAN_FS_ERROR (Amir)
>
> Changes since v1:
>   - Overload FS_ERROR with FS_IN_IGNORED
>   - Implement support for this type on fsnotify_data_inode (Amir)
> ---
>  fs/notify/fsnotify.c             |  3 +++
>  include/linux/fsnotify.h         | 13 +++++++++++++
>  include/linux/fsnotify_backend.h | 18 +++++++++++++++++-
>  3 files changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
> index 536db02cb26e..6d3b3de4f8ee 100644
> --- a/fs/notify/fsnotify.c
> +++ b/fs/notify/fsnotify.c
> @@ -103,6 +103,9 @@ static struct super_block *fsnotify_data_sb(const void *data, int data_type)
>         struct inode *inode = fsnotify_data_inode(data, data_type);
>         struct super_block *sb = inode ? inode->i_sb : NULL;
>
> +       if (!sb && data_type == FSNOTIFY_EVENT_ERROR)
> +               sb = ((struct fs_error_report *) data)->sb;
> +
>         return sb;
>  }
>
> diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
> index f8acddcf54fb..521234af1827 100644
> --- a/include/linux/fsnotify.h
> +++ b/include/linux/fsnotify.h
> @@ -317,4 +317,17 @@ static inline void fsnotify_change(struct dentry *dentry, unsigned int ia_valid)
>                 fsnotify_dentry(dentry, mask);
>  }
>
> +static inline int fsnotify_sb_error(struct super_block *sb, struct inode *inode,
> +                                   int error)
> +{
> +       struct fs_error_report report = {
> +               .error = error,
> +               .inode = inode,
> +               .sb = sb,
> +       };
> +
> +       return fsnotify(FS_ERROR, &report, FSNOTIFY_EVENT_ERROR,
> +                       NULL, NULL, NULL, 0);
> +}
> +
>  #endif /* _LINUX_FS_NOTIFY_H */
> diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
> index e027af3cd8dd..277b6f3e0998 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 +255,13 @@ 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;
> +       struct super_block *sb;
>  };
>
>  static inline struct inode *fsnotify_data_inode(const void *data, int data_type)
> @@ -257,6 +271,8 @@ static inline struct inode *fsnotify_data_inode(const void *data, int data_type)
>                 return (struct inode *)data;
>         case FSNOTIFY_EVENT_PATH:
>                 return d_inode(((const struct path *)data)->dentry);
> +       case FSNOTIFY_EVENT_ERROR:
> +               return ((struct fs_error_report *)data)->inode;
>         default:
>                 return NULL;
>         }
> --
> 2.32.0
>