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-rw-r--r--fs/open.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/open.c b/fs/open.c
index 1091dadd6c38..7d02d19bd0a2 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -890,6 +890,10 @@ EXPORT_SYMBOL(filp_open);
* a fully instantiated struct file to the caller.
* This function is meant to be called from within a filesystem's
* lookup method.
+ * Beware of calling it for non-regular files! Those ->open methods might block
+ * (e.g. in fifo_open), leaving you with parent locked (and in case of fifo,
+ * leading to a deadlock, as nobody can open that fifo anymore, because
+ * another process to open fifo will block on locked parent when doing lookup).
* Note that in case of error, nd->intent.open.file is destroyed, but the
* path information remains valid.
* If the open callback is set to NULL, then the standard f_op->open()