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

diff --git a/example/printcap.c b/example/printcap.c
index edfd8f53139a0dc37d869975617298aba444ad81..48679883c9e8a8bfd25bbfb6f21236ec83c0ebd8 100644 (file)
--- a/example/printcap.c
+++ b/example/printcap.c
@@ -81,6 +81,8 @@ static void pc_init(void *userdata,
                        printf("\tFUSE_CAP_NO_OPENDIR_SUPPORT\n");
        if(conn->capable & FUSE_CAP_EXPLICIT_INVAL_DATA)
                        printf("\tFUSE_CAP_EXPLICIT_INVAL_DATA\n");
+       if(conn->capable & FUSE_CAP_EXPIRE_ONLY)
+                       printf("\tFUSE_CAP_EXPIRE_ONLY\n");
        fuse_session_exit(se);
 }
 

diff --git a/include/fuse_common.h b/include/fuse_common.h
index e9d874556d838900aa35f918317dbe4858cfadee..dbba05af8e729bff6538d3a3185d99ac123339e4 100644 (file)
--- a/include/fuse_common.h
+++ b/include/fuse_common.h
@@ -408,6 +408,22 @@ 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
  *

diff --git a/include/fuse_lowlevel.h b/include/fuse_lowlevel.h
index cceb9be6a1e597e440c7666d75795505770fc279..6bad70ea4a62df4e54f2db9e078e470c79869067 100644 (file)
--- a/include/fuse_lowlevel.h
+++ b/include/fuse_lowlevel.h
@@ -127,6 +127,15 @@ struct fuse_forget_data {
        uint64_t nlookup;
 };
 
+/**
+ * Flags for fuse_lowlevel_notify_expire_entry()
+ * 0 = invalidate entry
+ * FUSE_LL_EXPIRE_ONLY = expire entry
+*/
+enum fuse_expire_flags {
+       FUSE_LL_EXPIRE_ONLY     = (1 << 0),
+};
+
 /* 'to_set' flags in setattr */
 #define FUSE_SET_ATTR_MODE     (1 << 0)
 #define FUSE_SET_ATTR_UID      (1 << 1)
@@ -1675,10 +1684,33 @@ int fuse_lowlevel_notify_inval_inode(struct fuse_session *se, fuse_ino_t ino,
 int fuse_lowlevel_notify_inval_entry(struct fuse_session *se, fuse_ino_t parent,
                                     const char *name, size_t namelen);
 
-enum fuse_expire_flags {
-       FUSE_LL_EXPIRE_ONLY     = (1 << 0),
-};
-
+/**
+ * Notify to expire or invalidate parent attributes and the dentry 
+ * matching parent/name
+ * 
+ * Underlying function for fuse_lowlevel_notify_inval_entry().
+ * 
+ * In addition to invalidating an entry, it also allows to expire an entry.
+ * In that case, the entry is not forcefully removed from kernel cache 
+ * but instead the next access to it forces a lookup from the filesystem.
+ * 
+ * This 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.
+ *
+ * @param se the session object
+ * @param parent inode number
+ * @param name file name
+ * @param namelen strlen() of file name
+ * @param flags flags to control if the entry should be expired or invalidated
+ * @return zero for success, -errno for failure
+*/
 int fuse_lowlevel_notify_expire_entry(struct fuse_session *se, fuse_ino_t parent,
                                       const char *name, size_t namelen,
                                       enum fuse_expire_flags flags);

diff --git a/lib/fuse_lowlevel.c b/lib/fuse_lowlevel.c
index 7b9d71043505f2e301fa66bb039e162565f1f9d7..7d76309254a4b57bbe73632356ea3557977d3539 100644 (file)
--- a/lib/fuse_lowlevel.c
+++ b/lib/fuse_lowlevel.c
@@ -1991,6 +1991,8 @@ void do_init(fuse_req_t req, fuse_ino_t nodeid, const void *inarg)
                                bufsize = max_bufsize;
                        }
                }
+               if (arg->minor >= 38)
+                       se->conn.capable |= FUSE_CAP_EXPIRE_ONLY;
        } else {
                se->conn.max_readahead = 0;
        }