fanotify: Support enqueueing of error events

Once an error event is triggered, enqueue it in the notification group,
similarly to what is done for other events.  FAN_FS_ERROR is not
handled specially, since the memory is now handled by a preallocated
mempool.

For now, make the event unhashed.  A future patch implements merging of
this kind of event.

Link: https://lore.kernel.org/r/20211025192746.66445-21-krisman@collabora.com
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/notify/fanotify/fanotify.c

@@ -574,6 +574,27 @@ static struct fanotify_event *fanotify_alloc_name_event(struct inode *id,
 	return &fne->fae;
 }
 
+static struct fanotify_event *fanotify_alloc_error_event(
+						struct fsnotify_group *group,
+						__kernel_fsid_t *fsid,
+						const void *data, int data_type)
+{
+	struct fs_error_report *report =
+			fsnotify_data_error_report(data, data_type);
+	struct fanotify_error_event *fee;
+
+	if (WARN_ON_ONCE(!report))
+		return NULL;
+
+	fee = mempool_alloc(&group->fanotify_data.error_events_pool, GFP_NOFS);
+	if (!fee)
+		return NULL;
+
+	fee->fae.type = FANOTIFY_EVENT_TYPE_FS_ERROR;
+
+	return &fee->fae;
+}
+
 static struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
 						   u32 mask, const void *data,
 						   int data_type, struct inode *dir,
@@ -641,6 +662,9 @@ static struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
 
 	if (fanotify_is_perm_event(mask)) {
 		event = fanotify_alloc_perm_event(path, gfp);
+	} else if (fanotify_is_error_event(mask)) {
+		event = fanotify_alloc_error_event(group, fsid, data,
+						   data_type);
 	} else if (name_event && (file_name || child)) {
 		event = fanotify_alloc_name_event(id, fsid, file_name, child,
 						  &hash, gfp);
@@ -850,6 +874,14 @@ static void fanotify_free_name_event(struct fanotify_event *event)
 	kfree(FANOTIFY_NE(event));
 }
 
+static void fanotify_free_error_event(struct fsnotify_group *group,
+				      struct fanotify_event *event)
+{
+	struct fanotify_error_event *fee = FANOTIFY_EE(event);
+
+	mempool_free(fee, &group->fanotify_data.error_events_pool);
+}
+
 static void fanotify_free_event(struct fsnotify_group *group,
 				struct fsnotify_event *fsn_event)
 {
@@ -873,6 +905,9 @@ static void fanotify_free_event(struct fsnotify_group *group,
 	case FANOTIFY_EVENT_TYPE_OVERFLOW:
 		kfree(event);
 		break;
+	case FANOTIFY_EVENT_TYPE_FS_ERROR:
+		fanotify_free_error_event(group, event);
+		break;
 	default:
 		WARN_ON_ONCE(1);
 	}

fs/notify/fanotify/fanotify.h

@@ -298,6 +298,11 @@ static inline struct fanotify_event *FANOTIFY_E(struct fsnotify_event *fse)
 	return container_of(fse, struct fanotify_event, fse);
 }
 
+static inline bool fanotify_is_error_event(u32 mask)
+{
+	return mask & FAN_FS_ERROR;
+}
+
 static inline bool fanotify_event_has_path(struct fanotify_event *event)
 {
 	return event->type == FANOTIFY_EVENT_TYPE_PATH ||
@@ -327,6 +332,7 @@ static inline struct path *fanotify_event_path(struct fanotify_event *event)
 static inline bool fanotify_is_hashed_event(u32 mask)
 {
 	return !(fanotify_is_perm_event(mask) ||
+		 fanotify_is_error_event(mask) ||
 		 fsnotify_is_overflow_event(mask));
 }