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References: <20211014213646.1139469-1-krisman@collabora.com> <20211014213646.1139469-25-krisman@collabora.com>
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From:   Amir Goldstein <amir73il@gmail.com>
Date:   Fri, 15 Oct 2021 11:13:43 +0300
Message-ID: <CAOQ4uxh21WmmVXWzx9UnNmJGwUGJN+sPwoMbuiUKFpf3cYJ7wA@mail.gmail.com>
Subject: Re: [PATCH v7 24/28] fanotify: Emit generic error info for error event
To:     Gabriel Krisman Bertazi <krisman@collabora.com>
Cc:     Jan Kara <jack@suse.com>, "Darrick J. Wong" <djwong@kernel.org>,
        Theodore Tso <tytso@mit.edu>,
        David Howells <dhowells@redhat.com>,
        Khazhismel Kumykov <khazhy@google.com>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Ext4 <linux-ext4@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>,
        Matthew Bobrowski <repnop@google.com>, kernel@collabora.com
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On Fri, Oct 15, 2021 at 12:39 AM Gabriel Krisman Bertazi
<krisman@collabora.com> wrote:
>
> The error info is a record sent to users on FAN_FS_ERROR events
> documenting the type of error.  It also carries an error count,
> documenting how many errors were observed since the last reporting.
>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>

>
> ---
> Changes since v6:
>   - Rebase on top of pidfd patches
> Changes since v5:
>   - Move error code here
> ---
>  fs/notify/fanotify/fanotify.c      |  1 +
>  fs/notify/fanotify/fanotify.h      |  1 +
>  fs/notify/fanotify/fanotify_user.c | 35 ++++++++++++++++++++++++++++++
>  include/uapi/linux/fanotify.h      |  7 ++++++
>  4 files changed, 44 insertions(+)
>
> diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
> index 8a60c96f5fb2..47e28f418711 100644
> --- a/fs/notify/fanotify/fanotify.c
> +++ b/fs/notify/fanotify/fanotify.c
> @@ -623,6 +623,7 @@ static struct fanotify_event *fanotify_alloc_error_event(
>                 return NULL;
>
>         fee->fae.type = FANOTIFY_EVENT_TYPE_FS_ERROR;
> +       fee->error = report->error;
>         fee->err_count = 1;
>         fee->fsid = *fsid;
>
> diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
> index b58400926f92..a0897425df07 100644
> --- a/fs/notify/fanotify/fanotify.h
> +++ b/fs/notify/fanotify/fanotify.h
> @@ -199,6 +199,7 @@ FANOTIFY_NE(struct fanotify_event *event)
>
>  struct fanotify_error_event {
>         struct fanotify_event fae;
> +       s32 error; /* Error reported by the Filesystem. */
>         u32 err_count; /* Suppressed errors count */
>
>         __kernel_fsid_t fsid; /* FSID this error refers to. */
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index 39cf8ba4a6ce..8f7c2f4ce674 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -115,6 +115,8 @@ struct kmem_cache *fanotify_perm_event_cachep __read_mostly;
>         (sizeof(struct fanotify_event_info_fid) + sizeof(struct file_handle))
>  #define FANOTIFY_PIDFD_INFO_HDR_LEN \
>         sizeof(struct fanotify_event_info_pidfd)
> +#define FANOTIFY_ERROR_INFO_LEN \
> +       (sizeof(struct fanotify_event_info_error))
>
>  static int fanotify_fid_info_len(int fh_len, int name_len)
>  {
> @@ -149,6 +151,9 @@ static size_t fanotify_event_len(unsigned int info_mode,
>         if (!info_mode)
>                 return event_len;
>
> +       if (fanotify_is_error_event(event->mask))
> +               event_len += FANOTIFY_ERROR_INFO_LEN;
> +
>         info = fanotify_event_info(event);
>         dir_fh_len = fanotify_event_dir_fh_len(event);
>         fh_len = fanotify_event_object_fh_len(event);
> @@ -333,6 +338,28 @@ static int process_access_response(struct fsnotify_group *group,
>         return -ENOENT;
>  }
>
> +static size_t copy_error_info_to_user(struct fanotify_event *event,
> +                                     char __user *buf, int count)
> +{
> +       struct fanotify_event_info_error info;
> +       struct fanotify_error_event *fee = FANOTIFY_EE(event);
> +
> +       info.hdr.info_type = FAN_EVENT_INFO_TYPE_ERROR;
> +       info.hdr.pad = 0;
> +       info.hdr.len = FANOTIFY_ERROR_INFO_LEN;
> +
> +       if (WARN_ON(count < info.hdr.len))
> +               return -EFAULT;
> +
> +       info.error = fee->error;
> +       info.error_count = fee->err_count;
> +
> +       if (copy_to_user(buf, &info, sizeof(info)))
> +               return -EFAULT;
> +
> +       return info.hdr.len;
> +}
> +
>  static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
>                                  int info_type, const char *name,
>                                  size_t name_len,
> @@ -540,6 +567,14 @@ static int copy_info_records_to_user(struct fanotify_event *event,
>                 total_bytes += ret;
>         }
>
> +       if (fanotify_is_error_event(event->mask)) {
> +               ret = copy_error_info_to_user(event, buf, count);
> +               if (ret < 0)
> +                       return ret;
> +               buf += ret;
> +               count -= ret;
> +       }
> +
>         return total_bytes;
>  }
>
> diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h
> index 2990731ddc8b..bd1932c2074d 100644
> --- a/include/uapi/linux/fanotify.h
> +++ b/include/uapi/linux/fanotify.h
> @@ -126,6 +126,7 @@ struct fanotify_event_metadata {
>  #define FAN_EVENT_INFO_TYPE_DFID_NAME  2
>  #define FAN_EVENT_INFO_TYPE_DFID       3
>  #define FAN_EVENT_INFO_TYPE_PIDFD      4
> +#define FAN_EVENT_INFO_TYPE_ERROR      5
>
>  /* Variable length info record following event metadata */
>  struct fanotify_event_info_header {
> @@ -160,6 +161,12 @@ struct fanotify_event_info_pidfd {
>         __s32 pidfd;
>  };
>
> +struct fanotify_event_info_error {
> +       struct fanotify_event_info_header hdr;
> +       __s32 error;
> +       __u32 error_count;
> +};
> +
>  struct fanotify_response {
>         __s32 fd;
>         __u32 response;
> --
> 2.33.0
>