adding comments and capability discovery, enum for flags moved to top of file

1 files changed, 16 insertions, 0 deletions

diff --git a/include/fuse_common.h b/include/fuse_common.h
index e9d8745..dbba05a 100644
--- a/include/fuse_common.h
+++ b/include/fuse_common.h
@@ -409,6 +409,22 @@ struct fuse_loop_config_v1 {
 #define FUSE_CAP_EXPLICIT_INVAL_DATA    (1 << 25)
 
 /**
+ * Indicates support that dentries can be expired or invalidated.
+ * 
+ * Expiring dentries, instead of invalidating them, makes a difference for 
+ * overmounted dentries, where plain invalidation would detach all submounts 
+ * before dropping the dentry from the cache. If only expiry is set on the 
+ * dentry, then any overmounts are left alone and until ->d_revalidate() 
+ * is called.
+ * 
+ * Note: ->d_revalidate() is not called for the case of following a submount,
+ * so invalidation will only be triggered for the non-overmounted case. 
+ * The dentry could also be mounted in a different mount instance, in which case
+ * any submounts will still be detached.
+*/
+#define FUSE_CAP_EXPIRE_ONLY      (1 << 26)
+
+/**
  * Ioctl flags
  *
  * FUSE_IOCTL_COMPAT: 32bit compat ioctl on 64bit machine