[PATCH v4 5/5] Use d_for_each_positive_child() in fsnotify.

[NeilBrown]

From: NeilBrown <neil@xxxxxxxxxx>

fsnotify has been reported as source of soft-lockups when iterating a
long ->d_children list.  Change it to use d_for_each_positive_child()
which will call cond_resched() as needed to avoid soft-lockups.

Link https://lwn.net/Articles/1079407/
Signed-off-by: NeilBrown <neil@xxxxxxxxxx>
---
 fs/notify/fsnotify.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index 465e875dec57..62c17e4e4798 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -86,16 +86,12 @@ void fsnotify_set_children_dentry_flags(struct inode *inode)
 	 * d_flags to indicate parental interest (their parent is the
 	 * original inode)
 	 */
-	spin_lock(&alias->d_lock);
-	hlist_for_each_entry(child, &alias->d_children, d_sib) {
-		if (!child->d_inode)
-			continue;
 
+	d_for_each_positive_child(child, alias) {
 		spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
 		child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
 		spin_unlock(&child->d_lock);
 	}
-	spin_unlock(&alias->d_lock);
 	dput(alias);
 }
 
-- 
2.50.0.107.gf914562f5916.dirty