[PATCH v3 22/38] vfs: add fsnotify_modify_mark_mask()

[Jeff Layton <jlayton@kernel.org>]

nfsd needs to be able to modify the mask on an existing mark when new
directory delegations are set or unset. Add an exported function that
allows the caller to set and clear bits in the mark->mask, and does
the recalculation if something changed.

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/notify/mark.c                 | 29 +++++++++++++++++++++++++++++
 include/linux/fsnotify_backend.h |  1 +
 2 files changed, 30 insertions(+)

diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 798340db69d761dd05c1b361c251818dee89b9cf..5ed42b24df7f6aa3812a7069b4c37f0c6b3414fa 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -309,6 +309,35 @@ void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn)
 		fsnotify_conn_set_children_dentry_flags(conn);
 }
 
+/**
+ * fsnotify_modify_mark_mask - set and/or clear flags in a mark's mask
+ * @mark: mark to be modified
+ * @set: bits to be set in mask
+ * @clear: bits to be cleared in mask
+ *
+ * Modify a fsnotify_mark mask as directed, and update its associated conn.
+ * The caller is expected to hold a reference to the mark.
+ */
+void fsnotify_modify_mark_mask(struct fsnotify_mark *mark, u32 set, u32 clear)
+{
+	bool recalc = false;
+	u32 mask;
+
+	WARN_ON_ONCE(clear & set);
+
+	spin_lock(&mark->lock);
+	mask = mark->mask;
+	mark->mask |= set;
+	mark->mask &= ~clear;
+	if (mark->mask != mask)
+		recalc = true;
+	spin_unlock(&mark->lock);
+
+	if (recalc)
+		fsnotify_recalc_mask(mark->connector);
+}
+EXPORT_SYMBOL_GPL(fsnotify_modify_mark_mask);
+
 /* Free all connectors queued for freeing once SRCU period ends */
 static void fsnotify_connector_destroy_workfn(struct work_struct *work)
 {
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index d4034ddaf3926bf98d8801997e50ba7ddf776292..8d50e6aad3c62c67a9bf73a8d9aab78565668c5f 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -912,6 +912,7 @@ extern void fsnotify_get_mark(struct fsnotify_mark *mark);
 extern void fsnotify_put_mark(struct fsnotify_mark *mark);
 extern void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info);
 extern bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info);
+extern void fsnotify_modify_mark_mask(struct fsnotify_mark *mark, u32 set, u32 clear);
 
 static inline void fsnotify_init_event(struct fsnotify_event *event)
 {

-- 
2.51.0