Merge tag 'fsnotify_for_v5.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs

Pull fsnotify updates from Jan Kara:

 - support for FAN_MARK_IGNORE which untangles some of the not well
   defined corner cases with fanotify ignore masks

 - small cleanups

* tag 'fsnotify_for_v5.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
  fsnotify: Fix comment typo
  fanotify: introduce FAN_MARK_IGNORE
  fanotify: cleanups for fanotify_mark() input validations
  fanotify: prepare for setting event flags in ignore mask
  fs: inotify: Fix typo in inotify comment

3 files changed, 100 insertions, 11 deletions

diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h
index e517dbcf74ed..8ad743def6f3 100644
--- a/include/linux/fanotify.h
+++ b/include/linux/fanotify.h
@@ -59,15 +59,19 @@
 #define FANOTIFY_MARK_TYPE_BITS	(FAN_MARK_INODE | FAN_MARK_MOUNT | \
 				 FAN_MARK_FILESYSTEM)
 
+#define FANOTIFY_MARK_CMD_BITS	(FAN_MARK_ADD | FAN_MARK_REMOVE | \
+				 FAN_MARK_FLUSH)
+
+#define FANOTIFY_MARK_IGNORE_BITS (FAN_MARK_IGNORED_MASK | \
+				   FAN_MARK_IGNORE)
+
 #define FANOTIFY_MARK_FLAGS	(FANOTIFY_MARK_TYPE_BITS | \
-				 FAN_MARK_ADD | \
-				 FAN_MARK_REMOVE | \
+				 FANOTIFY_MARK_CMD_BITS | \
+				 FANOTIFY_MARK_IGNORE_BITS | \
 				 FAN_MARK_DONT_FOLLOW | \
 				 FAN_MARK_ONLYDIR | \
-				 FAN_MARK_IGNORED_MASK | \
 				 FAN_MARK_IGNORED_SURV_MODIFY | \
-				 FAN_MARK_EVICTABLE | \
-				 FAN_MARK_FLUSH)
+				 FAN_MARK_EVICTABLE)
 
 /*
  * Events that can be reported with data type FSNOTIFY_EVENT_PATH.
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index 9560734759fa..d7d96c806bff 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -518,8 +518,8 @@ struct fsnotify_mark {
 	struct hlist_node obj_list;
 	/* Head of list of marks for an object [mark ref] */
 	struct fsnotify_mark_connector *connector;
-	/* Events types to ignore [mark->lock, group->mark_mutex] */
-	__u32 ignored_mask;
+	/* Events types and flags to ignore [mark->lock, group->mark_mutex] */
+	__u32 ignore_mask;
 	/* General fsnotify mark flags */
 #define FSNOTIFY_MARK_FLAG_ALIVE		0x0001
 #define FSNOTIFY_MARK_FLAG_ATTACHED		0x0002
@@ -529,6 +529,7 @@ struct fsnotify_mark {
 	/* fanotify mark flags */
 #define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY	0x0100
 #define FSNOTIFY_MARK_FLAG_NO_IREF		0x0200
+#define FSNOTIFY_MARK_FLAG_HAS_IGNORE_FLAGS	0x0400
 	unsigned int flags;		/* flags [mark->lock] */
 };
 
@@ -655,15 +656,91 @@ extern void fsnotify_remove_queued_event(struct fsnotify_group *group,
 
 /* functions used to manipulate the marks attached to inodes */
 
-/* Get mask for calculating object interest taking ignored mask into account */
+/*
+ * Canonical "ignore mask" including event flags.
+ *
+ * Note the subtle semantic difference from the legacy ->ignored_mask.
+ * ->ignored_mask traditionally only meant which events should be ignored,
+ * while ->ignore_mask also includes flags regarding the type of objects on
+ * which events should be ignored.
+ */
+static inline __u32 fsnotify_ignore_mask(struct fsnotify_mark *mark)
+{
+	__u32 ignore_mask = mark->ignore_mask;
+
+	/* The event flags in ignore mask take effect */
+	if (mark->flags & FSNOTIFY_MARK_FLAG_HAS_IGNORE_FLAGS)
+		return ignore_mask;
+
+	/*
+	 * Legacy behavior:
+	 * - Always ignore events on dir
+	 * - Ignore events on child if parent is watching children
+	 */
+	ignore_mask |= FS_ISDIR;
+	ignore_mask &= ~FS_EVENT_ON_CHILD;
+	ignore_mask |= mark->mask & FS_EVENT_ON_CHILD;
+
+	return ignore_mask;
+}
+
+/* Legacy ignored_mask - only event types to ignore */
+static inline __u32 fsnotify_ignored_events(struct fsnotify_mark *mark)
+{
+	return mark->ignore_mask & ALL_FSNOTIFY_EVENTS;
+}
+
+/*
+ * Check if mask (or ignore mask) should be applied depending if victim is a
+ * directory and whether it is reported to a watching parent.
+ */
+static inline bool fsnotify_mask_applicable(__u32 mask, bool is_dir,
+					    int iter_type)
+{
+	/* Should mask be applied to a directory? */
+	if (is_dir && !(mask & FS_ISDIR))
+		return false;
+
+	/* Should mask be applied to a child? */
+	if (iter_type == FSNOTIFY_ITER_TYPE_PARENT &&
+	    !(mask & FS_EVENT_ON_CHILD))
+		return false;
+
+	return true;
+}
+
+/*
+ * Effective ignore mask taking into account if event victim is a
+ * directory and whether it is reported to a watching parent.
+ */
+static inline __u32 fsnotify_effective_ignore_mask(struct fsnotify_mark *mark,
+						   bool is_dir, int iter_type)
+{
+	__u32 ignore_mask = fsnotify_ignored_events(mark);
+
+	if (!ignore_mask)
+		return 0;
+
+	/* For non-dir and non-child, no need to consult the event flags */
+	if (!is_dir && iter_type != FSNOTIFY_ITER_TYPE_PARENT)
+		return ignore_mask;
+
+	ignore_mask = fsnotify_ignore_mask(mark);
+	if (!fsnotify_mask_applicable(ignore_mask, is_dir, iter_type))
+		return 0;
+
+	return ignore_mask & ALL_FSNOTIFY_EVENTS;
+}
+
+/* Get mask for calculating object interest taking ignore mask into account */
 static inline __u32 fsnotify_calc_mask(struct fsnotify_mark *mark)
 {
 	__u32 mask = mark->mask;
 
-	if (!mark->ignored_mask)
+	if (!fsnotify_ignored_events(mark))
 		return mask;
 
-	/* Interest in FS_MODIFY may be needed for clearing ignored mask */
+	/* Interest in FS_MODIFY may be needed for clearing ignore mask */
 	if (!(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
 		mask |= FS_MODIFY;
 
@@ -671,7 +748,7 @@ static inline __u32 fsnotify_calc_mask(struct fsnotify_mark *mark)
 	 * If mark is interested in ignoring events on children, the object must
 	 * show interest in those events for fsnotify_parent() to notice it.
 	 */
-	return mask | (mark->ignored_mask & ALL_FSNOTIFY_EVENTS);
+	return mask | mark->ignore_mask;
 }
 
 /* Get mask of events for a list of marks */
diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h
index f1f89132d60e..d8536d77fea1 100644
--- a/include/uapi/linux/fanotify.h
+++ b/include/uapi/linux/fanotify.h
@@ -83,12 +83,20 @@
 #define FAN_MARK_FLUSH		0x00000080
 /* FAN_MARK_FILESYSTEM is	0x00000100 */
 #define FAN_MARK_EVICTABLE	0x00000200
+/* This bit is mutually exclusive with FAN_MARK_IGNORED_MASK bit */
+#define FAN_MARK_IGNORE		0x00000400
 
 /* These are NOT bitwise flags.  Both bits can be used togther.  */
 #define FAN_MARK_INODE		0x00000000
 #define FAN_MARK_MOUNT		0x00000010
 #define FAN_MARK_FILESYSTEM	0x00000100
 
+/*
+ * Convenience macro - FAN_MARK_IGNORE requires FAN_MARK_IGNORED_SURV_MODIFY
+ * for non-inode mark types.
+ */
+#define FAN_MARK_IGNORE_SURV	(FAN_MARK_IGNORE | FAN_MARK_IGNORED_SURV_MODIFY)
+
 /* Deprecated - do not use this in programs and do not add new flags here! */
 #define FAN_ALL_MARK_FLAGS	(FAN_MARK_ADD |\
 				 FAN_MARK_REMOVE |\