Make xs_mkdir an xs_rm idempotent.

When modifying libxenstore to transparently restart when the daemon dies,
it became apparent that life is simpler when all commands can simply be
restarted.  So this patch makes a slight semantic change to xs_rm and xs_mkdir: 
xs_rm now succeeds if the file doesn't exist (as long as the parent exists),
and xs_mkdir succeeds if the directory already exists.
Noone should notice.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>

6 files changed, 31 insertions, 16 deletions

diff --git a/tools/xenstore/testsuite/02directory.test b/tools/xenstore/testsuite/02directory.test
index 425026ffbe..fd57bb8b78 100644
--- a/tools/xenstore/testsuite/02directory.test
+++ b/tools/xenstore/testsuite/02directory.test
@@ -27,10 +27,8 @@ dir /dir
 expect contents2
 read /dir/test2
 
-# Creating dir over the top should fail.
-expect mkdir failed: File exists
+# Creating dir over the top should succeed.
 mkdir /dir
-expect mkdir failed: File exists
 mkdir /dir/test2
 
 # Mkdir implicitly creates directories.
diff --git a/tools/xenstore/testsuite/04rm.test b/tools/xenstore/testsuite/04rm.test
index 186e9a9d75..bcc035bac2 100644
--- a/tools/xenstore/testsuite/04rm.test
+++ b/tools/xenstore/testsuite/04rm.test
@@ -1,5 +1,4 @@
-# Remove non-existant fails.
-expect rm failed: No such file or directory
+# Remove non-existant is OK, as long as parent exists
 rm /test
 expect rm failed: No such file or directory
 rm /dir/test
diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
index 564b7dce38..f5e7d0c9f3 100644
--- a/tools/xenstore/xenstored_core.c
+++ b/tools/xenstore/xenstored_core.c
@@ -961,6 +961,13 @@ static char *tempdir(struct connection *conn,
 	return dir;
 }
 
+static bool node_exists(struct connection *conn, const char *node)
+{
+	struct stat st;
+
+	return lstat(node_dir(conn->transaction, node), &st) == 0;
+}
+
 /* path, flags, data... */
 static void do_write(struct connection *conn, struct buffered_data *in)
 {
@@ -1050,7 +1057,6 @@ static void do_write(struct connection *conn, struct buffered_data *in)
 static void do_mkdir(struct connection *conn, const char *node)
 {
 	char *dir;
-	struct stat st;
 
 	node = canonicalize(conn, node);
 	if (!check_node_perms(conn, node, XS_PERM_WRITE|XS_PERM_ENOENT_OK)) {
@@ -1066,9 +1072,9 @@ static void do_mkdir(struct connection *conn, const char *node)
 	if (transaction_block(conn, node))
 		return;
 
-	/* Must not already exist. */
-	if (lstat(node_dir(conn->transaction, node), &st) == 0) {
-		send_error(conn, EEXIST);
+	/* If it already exists, fine. */
+	if (node_exists(conn, node)) {
+		send_ack(conn, XS_MKDIR);
 		return;
 	}
 
@@ -1089,6 +1095,15 @@ static void do_rm(struct connection *conn, const char *node)
 
 	node = canonicalize(conn, node);
 	if (!check_node_perms(conn, node, XS_PERM_WRITE)) {
+		/* Didn't exist already?  Fine, if parent exists. */
+		if (errno == ENOENT) {
+			if (node_exists(conn, get_parent(node))) {
+				send_ack(conn, XS_RM);
+				return;
+			}
+			/* Restore errno, just in case. */
+			errno = ENOENT;
+		}
 		send_error(conn, errno);
 		return;
 	}
diff --git a/tools/xenstore/xs.c b/tools/xenstore/xs.c
index 9991cefc61..ad17e9d31a 100644
--- a/tools/xenstore/xs.c
+++ b/tools/xenstore/xs.c
@@ -357,7 +357,7 @@ bool xs_write(struct xs_handle *h, const char *path,
 }
 
 /* Create a new directory.
- * Returns false on failure.
+ * Returns false on failure, or success if it already exists.
  */
 bool xs_mkdir(struct xs_handle *h, const char *path)
 {
@@ -365,7 +365,7 @@ bool xs_mkdir(struct xs_handle *h, const char *path)
 }
 
 /* Destroy a file or directory (directories must be empty).
- * Returns false on failure.
+ * Returns false on failure, or success if it doesn't exist.
  */
 bool xs_rm(struct xs_handle *h, const char *path)
 {
diff --git a/tools/xenstore/xs.h b/tools/xenstore/xs.h
index 5999baaa00..98679eebd2 100644
--- a/tools/xenstore/xs.h
+++ b/tools/xenstore/xs.h
@@ -59,12 +59,12 @@ bool xs_write(struct xs_handle *h, const char *path, const void *data,
 	      unsigned int len, int createflags);
 
 /* Create a new directory.
- * Returns false on failure.
+ * Returns false on failure, or success if it already exists.
  */
 bool xs_mkdir(struct xs_handle *h, const char *path);
 
 /* Destroy a file or directory (and children).
- * Returns false on failure.
+ * Returns false on failure, or success if it doesn't exist.
  */
 bool xs_rm(struct xs_handle *h, const char *path);
 
diff --git a/tools/xenstore/xs_random.c b/tools/xenstore/xs_random.c
index b8f39d36e7..7a2119ccf7 100644
--- a/tools/xenstore/xs_random.c
+++ b/tools/xenstore/xs_random.c
@@ -385,7 +385,7 @@ static bool file_mkdir(struct file_ops_info *info, const char *path)
 
 	make_dirs(parent_filename(dirname));
 	if (mkdir(dirname, 0700) != 0)
-		return false;
+		return (errno == EEXIST);
 
 	init_perms(dirname);
 	return true;
@@ -401,8 +401,11 @@ static bool file_rm(struct file_ops_info *info, const char *path)
 		return false;
 	}
 
-	if (lstat(filename, &st) != 0)
-		return false;
+	if (lstat(filename, &st) != 0) {
+		if (lstat(parent_filename(filename), &st) != 0)
+			return false;
+		return true;
+	}
 
 	if (!write_ok(info, path))
 		return false;