Changeset e4e546b in mainline

Timestamp:

2017-03-22T19:26:21Z (7 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

c68edd2

Parents:

c990ee6

Message:

Fix L_CREATE and L_UNLINK across mountpoints

Server-side mountpoints broke linking of the first name and unlinking of
the last name of a file across mountpoints. In order to do the expected
thing, both operations need to be split into a mere lookup phase to
locate the parent of the added/removed name, and a link/unlink phase
that adds/removes the name to/from the parent node.

File:

• uspace/srv/vfs/vfs_lookup.c (modified) (2 diffs)

uspace/srv/vfs/vfs_lookup.c

@@ -238 +238 @@
 }
 
-/** Perform a path lookup.
- *
- * @param base    The file from which to perform the lookup.
- * @param path    Path to be resolved; it must be a NULL-terminated
- *                string.
- * @param lflag   Flags to be used during lookup.
- * @param result  Empty structure where the lookup result will be stored.
- *                Can be NULL.
- *
- * @return EOK on success or an error code from errno.h.
- *
- */
-int vfs_lookup_internal(vfs_node_t *base, char *path, int lflag,
-    vfs_lookup_res_t *result)
-{
-        assert(base != NULL);
-        assert(path != NULL);
-        
-        size_t len;
+static int _vfs_lookup_internal(vfs_node_t *base, char *path, int lflag,
+    vfs_lookup_res_t *result, size_t len)
+{
+        size_t first;
         int rc;
-        char *npath = canonify(path, &len);
-        if (!npath) {
-                rc = EINVAL;
-                return rc;
-        }
-        path = npath;
-        
-        assert(path[0] == '/');
-        
-        size_t first;
-        
+
         plb_entry_t entry;
         rc = plb_insert_entry(&entry, path, &first, len);
@@ -347 +322 @@
 }
 
+/** Perform a path lookup.
+ *
+ * @param base    The file from which to perform the lookup.
+ * @param path    Path to be resolved; it must be a NULL-terminated
+ *                string.
+ * @param lflag   Flags to be used during lookup.
+ * @param result  Empty structure where the lookup result will be stored.
+ *                Can be NULL.
+ *
+ * @return EOK on success or an error code from errno.h.
+ *
+ */
+int vfs_lookup_internal(vfs_node_t *base, char *path, int lflag,
+    vfs_lookup_res_t *result)
+{
+        assert(base != NULL);
+        assert(path != NULL);
+        
+        size_t len;
+        int rc;
+        char *npath = canonify(path, &len);
+        if (!npath) {
+                rc = EINVAL;
+                return rc;
+        }
+        path = npath;
+        
+        assert(path[0] == '/');
+
+
+        if (lflag & (L_CREATE | L_UNLINK)) {
+
+                /*
+                 * Creation and destruction of names must be done in two
+                 * separate steps: lookup of the parent node and the name
+                 * link/unlink operation itself.  Otherwise the parent
+                 * filesystem would not be able to tell when a mountpoint is
+                 * crossed. It would attempt to perform the link/unlink in
+                 * itself instead of letting the mounted filesystem do it,
+                 * resulting in wrong behavior. This is the wages of server-side
+                 * mountpoints.
+                 */
+
+                char *slash = str_rchr(path, L'/');
+                vfs_node_t *parent = base;
+                
+                if (slash != path) {
+                        int tflag = lflag;
+                        vfs_lookup_res_t tres;
+
+                        tflag &= ~(L_CREATE | L_EXCLUSIVE | L_UNLINK | L_FILE);
+                        tflag |= L_DIRECTORY;
+                        rc = _vfs_lookup_internal(base, path, tflag, &tres,
+                            slash - path);
+                        if (rc != EOK)
+                                return rc;
+                        parent = vfs_node_get(&tres);
+                        if (!parent)
+                                return ENOMEM;
+                } else
+                        vfs_node_addref(parent);
+
+                rc = _vfs_lookup_internal(parent, slash, lflag, result,
+                    len - (slash - path));
+
+                vfs_node_put(parent);
+
+        } else {
+                rc = _vfs_lookup_internal(base, path, lflag, result, len);
+        }
+        
+        return rc;
+}
+
 /**
  * @}