[sheepdog] [PATCH v3 06/15] sheepfs: implement shadow file mechanism

[Liu Yuan]

From: Liu Yuan <tailai.ly at taobao.com>

Sheepfs use this shadow file mechanism to mostly manage dentries. We
might also make use of those shadow file to cache non-volatile states.

Signed-off-by: Liu Yuan <tailai.ly at taobao.com>
---
 sheepfs/Makefile.am   |    2 +-
 sheepfs/shadow_file.c |  150 +++++++++++++++++++++++++++++++++++++++++++++++++
 sheepfs/sheepfs.h     |   12 ++++
 3 files changed, 163 insertions(+), 1 deletion(-)
 create mode 100644 sheepfs/shadow_file.c

diff --git a/sheepfs/Makefile.am b/sheepfs/Makefile.am
index 17ac0fe..f6201a6 100644
--- a/sheepfs/Makefile.am
+++ b/sheepfs/Makefile.am
@@ -23,7 +23,7 @@ INCLUDES		= -I$(top_builddir)/include -I$(top_srcdir)/include
 
 sbin_PROGRAMS		= sheepfs
 
-sheepfs_SOURCES		= core.c cluster.c vdi.c
+sheepfs_SOURCES		= core.c cluster.c vdi.c shadow_file.c
 
 sheepfs_LDADD	  	= ../lib/libsheepdog.a $(fuse_LIBS) $(LIBS)
 sheepfs_DEPENDENCIES	= ../lib/libsheepdog.a
diff --git a/sheepfs/shadow_file.c b/sheepfs/shadow_file.c
new file mode 100644
index 0000000..033d4be
--- /dev/null
+++ b/sheepfs/shadow_file.c
@@ -0,0 +1,150 @@
+/*
+ * Copyright (C) 2012 Taobao Inc.
+ *
+ * Liu Yuan <namei.unix at gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version
+ * 2 as published by the Free Software Foundation.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ *  Sheepfs use this shadow file mechanism to mostly manage dentries. We
+ *  might also make use of those shadow file to cache non-volatile states.
+ */
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <stdio.h>
+#include <attr/xattr.h>
+#include <syslog.h>
+#include <stdlib.h>
+
+#include "util.h"
+#include "sheepfs.h"
+
+int shadow_file_read(const char *path, char *buf, size_t size, off_t offset)
+{
+	char p[PATH_MAX];
+	int fd, len;
+
+	sprintf(p, "%s%s", sheepfs_shadow, path);
+	fd = open(p, O_RDONLY);
+	if (fd < 0) {
+		syslog(LOG_ERR, "[%s] %m\n", __func__);
+		return -errno;
+	}
+	len = xpread(fd, buf, size, offset);
+	close(fd);
+	return len;
+}
+
+size_t shadow_file_write(const char *path, char *buf, size_t size)
+{
+	char p[PATH_MAX];
+	int fd;
+	size_t len = 0;
+
+	sprintf(p, "%s%s", sheepfs_shadow, path);
+	fd = open(p, O_WRONLY | O_TRUNC);
+	if (fd < 0) {
+		syslog(LOG_ERR, "[%s] %m\n", __func__);
+		return 0;
+	}
+	len = xwrite(fd, buf, size);
+	if (len != size) {
+		syslog(LOG_ERR, "[%s] failed to write\n", __func__);
+		len = 0;
+	}
+	close(fd);
+	return len;
+}
+
+int shadow_file_create(const char *path)
+{
+	char p[PATH_MAX];
+	int fd;
+	sprintf(p, "%s%s", sheepfs_shadow, path);
+	fd = creat(p, 0644);
+	if (fd < 0) {
+		if (errno != EEXIST) {
+			syslog(LOG_ERR, "[%s] %m\n", __func__);
+			return -1;
+		}
+	}
+	close(fd);
+	return 0;
+}
+
+int shadow_dir_create(const char *path)
+{
+	char p[PATH_MAX];
+
+	sprintf(p, "%s%s", sheepfs_shadow, path);
+	if (mkdir(p, 0755) < 0) {
+		if (errno != EEXIST) {
+			syslog(LOG_ERR, "[%s] %m\n", __func__);
+			return -1;
+		}
+	}
+	return 0;
+}
+
+int shadow_file_setxattr(const char *path, const char *name,
+		const void *value, size_t size)
+{
+	char p[PATH_MAX];
+
+	sprintf(p, "%s%s", sheepfs_shadow, path);
+	if (setxattr(p, name, value, size, 0) < 0) {
+		syslog(LOG_ERR, "[%s] %m\n", __func__);
+		return -1;
+	}
+	return 0;
+}
+
+int shadow_file_getxattr(const char *path, const char *name,
+		void *value, size_t size)
+{
+	char p[PATH_MAX];
+
+	sprintf(p, "%s%s", sheepfs_shadow, path);
+	if (getxattr(p, name, value, size) < 0) {
+		syslog(LOG_ERR, "[%s] %m\n", __func__);
+		return -1;
+	}
+	return 0;
+}
+
+int shadow_file_delete(const char *path)
+{
+	char p[PATH_MAX];
+
+	sprintf(p, "%s%s", sheepfs_shadow, path);
+	if (unlink(p) < 0) {
+		if (errno != ENOENT) {
+			syslog(LOG_ERR, "[%s] %m\n", __func__);
+			return -1;
+		}
+	}
+	return 0;
+}
+
+int shadow_file_exsit(const char *path)
+{
+	char p[PATH_MAX];
+
+	sprintf(p, "%s%s", sheepfs_shadow, path);
+	if (access(p, R_OK | W_OK) < 0) {
+		if (errno != ENOENT)
+			syslog(LOG_ERR, "[%s] %m\n", __func__);
+		return 0;
+	}
+
+        return 1;
+}
diff --git a/sheepfs/sheepfs.h b/sheepfs/sheepfs.h
index 4b20807..48f3dbc 100644
--- a/sheepfs/sheepfs.h
+++ b/sheepfs/sheepfs.h
@@ -13,6 +13,18 @@ extern char sheepfs_shadow[];
 extern struct strbuf *sheepfs_run_cmd(const char *command);
 extern int sheepfs_set_op(const char *path, unsigned opcode);
 
+/* shadow_file.c */
+extern size_t shadow_file_write(const char *path, char *buf, size_t size);
+extern int shadow_file_read(const char *, char *buf, size_t size, off_t);
+extern int shadow_dir_create(const char *path);
+extern int shadow_file_create(const char *path);
+extern int shadow_file_setxattr(const char *path, const char *name,
+				const void *value, size_t size);
+extern int shadow_file_getxattr(const char *path, const char *name,
+				void *value, size_t size);
+extern int shadow_file_delete(const char *path);
+extern int shadow_file_exsit(const char *path);
+
 /* cluster.c */
 extern int cluster_info_read(const char *path, char *buf, size_t size, off_t);
 extern size_t cluster_info_get_size(const char *path);
-- 
1.7.10.2