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Date:   Fri, 15 Oct 2021 14:47:01 +0200
From:   Jan Kara <jack@suse.cz>
To:     Gabriel Krisman Bertazi <krisman@collabora.com>
Cc:     jack@suse.com, amir73il@gmail.com, djwong@kernel.org,
        tytso@mit.edu, dhowells@redhat.com, khazhy@google.com,
        linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
        linux-api@vger.kernel.org, repnop@google.com, kernel@collabora.com
Subject: Re: [PATCH v7 24/28] fanotify: Emit generic error info for error
 event
Message-ID: <20211015124701.GL23102@quack2.suse.cz>
References: <20211014213646.1139469-1-krisman@collabora.com>
 <20211014213646.1139469-25-krisman@collabora.com>
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On Thu 14-10-21 18:36:42, Gabriel Krisman Bertazi 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>

Looks good to me. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> 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
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR