diff --git a/components/dfs/src/dfs.c b/components/dfs/src/dfs.c
index 7ac596a2a03ec2cb50b78db8cba50ddbb68082c1..3db6e5169481a54510cf3cfd58ccd5beb5a3f9ff 100644
--- a/components/dfs/src/dfs.c
+++ b/components/dfs/src/dfs.c
@@ -142,10 +142,10 @@ struct dfs_fd *fd_get(int fd)
 	struct dfs_fd *d;
 
 #ifdef DFS_USING_STDIO
-	if (fd < 3 || fd > DFS_FD_MAX + 3) 
+	if (fd < 3 || fd >= DFS_FD_MAX + 3)
 		return RT_NULL;
 #else
-	if (fd < 0 || fd > DFS_FD_MAX) 
+	if (fd < 0 || fd >= DFS_FD_MAX)
 		return RT_NULL;
 #endif
 
@@ -166,6 +166,8 @@ struct dfs_fd *fd_get(int fd)
  */
 void fd_put(struct dfs_fd *fd)
 {
+	RT_ASSERT(fd != RT_NULL);
+
 	dfs_lock();
 	fd->ref_count --;
 
diff --git a/components/dfs/src/dfs_file.c b/components/dfs/src/dfs_file.c
index 3c9897fc774bcbe531336d0747a09c1d3e0a02af..a9e4241ac220ddcd646f465f6dac81b09c50e4a8 100644
--- a/components/dfs/src/dfs_file.c
+++ b/components/dfs/src/dfs_file.c
@@ -60,7 +60,7 @@ int dfs_file_open(struct dfs_fd *fd, const char *path, int flags)
 	dfs_log(DFS_DEBUG_INFO, ("open in filesystem:%s", fs->ops->name));
 	fd->fs = fs;
 
-	/* initilize the fd item */
+	/* initialize the fd item */
 	fd->type = FT_REGULAR;
 	fd->flags = flags;
 	fd->size = 0;
diff --git a/components/dfs/src/dfs_posix.c b/components/dfs/src/dfs_posix.c
index f9608e4ac592bd626acace6cb97d8dede186775e..ea6ba198108ee36196dea1c11f975ecd6076485c 100644
--- a/components/dfs/src/dfs_posix.c
+++ b/components/dfs/src/dfs_posix.c
@@ -38,7 +38,10 @@ int open(const char *file, int flags, int mode)
 	/* allocate a fd */
 	fd = fd_new();
 	if (fd < 0)
+	{
+		rt_set_errno(-DFS_STATUS_ENOMEM);
 		return -1;
+	}
 	d  = fd_get(fd);
 
 	result = dfs_file_open(d, file, flags);
@@ -74,7 +77,7 @@ int close(int fd)
 	d = fd_get(fd);
 	if (d == RT_NULL)
 	{
-		rt_set_errno(-RT_ERROR);
+		rt_set_errno(-DFS_STATUS_EBADF);
 		return -1;
 	}
 
@@ -110,7 +113,7 @@ int read(int fd, void *buf, size_t len)
 	d  = fd_get(fd);
 	if (d == RT_NULL)
 	{
-		rt_set_errno(-RT_ERROR);
+		rt_set_errno(-DFS_STATUS_EBADF);
 		return -1;
 	}
 
@@ -147,7 +150,7 @@ int write(int fd, const void *buf, size_t len)
 	d  = fd_get(fd);
 	if (d == RT_NULL)
 	{
-		rt_set_errno(-RT_ERROR);
+		rt_set_errno(-DFS_STATUS_EBADF);
 		return -1;
 	}
 
@@ -183,7 +186,7 @@ off_t lseek(int fd, off_t offset, int whence)
 	d = fd_get(fd);
 	if (d == RT_NULL)
 	{
-		rt_set_errno(-RT_ERROR);
+		rt_set_errno(-DFS_STATUS_EBADF);
 		return -1;
 	}
 
@@ -304,7 +307,7 @@ int fstat(int fildes, struct stat *buf)
 	d = fd_get(fildes);
 	if (d == RT_NULL)
 	{
-		rt_set_errno(-RT_ERROR);
+		rt_set_errno(-DFS_STATUS_EBADF);
 		return -1;
 	}
 
@@ -368,7 +371,7 @@ int mkdir(const char *path, mode_t mode)
 	fd = fd_new();
 	if (fd == -1)
 	{
-		rt_kprintf("no fd\n");
+		rt_set_errno(-DFS_STATUS_ENOMEM);
 		return -1;
 	}
 
@@ -432,7 +435,7 @@ DIR *opendir(const char *name)
 	fd = fd_new();
 	if (fd == -1)
 	{
-		rt_kprintf("no fd\n");
+		rt_set_errno(-DFS_STATUS_ENOMEM);
 		return RT_NULL;
 	}
 	d = fd_get(fd);
@@ -481,7 +484,7 @@ struct dirent *readdir(DIR *d)
 	fd = fd_get(d->fd);
 	if (fd == RT_NULL)
 	{
-		rt_set_errno(-RT_ERROR);
+		rt_set_errno(-DFS_STATUS_EBADF);
 		return RT_NULL;
 	}
 
@@ -521,7 +524,7 @@ long telldir(DIR *d)
 	fd = fd_get(d->fd);
 	if (fd == RT_NULL)
 	{
-		rt_set_errno(-RT_ERROR);
+		rt_set_errno(-DFS_STATUS_EBADF);
 		return 0;
 	}
 
@@ -545,7 +548,7 @@ void seekdir(DIR *d, off_t offset)
 	fd = fd_get(d->fd);
 	if (fd == RT_NULL)
 	{
-		rt_set_errno(-RT_ERROR);
+		rt_set_errno(-DFS_STATUS_EBADF);
 		return ;
 	}
 
@@ -567,7 +570,7 @@ void rewinddir(DIR *d)
 	fd = fd_get(d->fd);
 	if (fd == RT_NULL)
 	{
-		rt_set_errno(-RT_ERROR);
+		rt_set_errno(-DFS_STATUS_EBADF);
 		return ;
 	}
 
@@ -593,7 +596,7 @@ int closedir(DIR *d)
 	fd = fd_get(d->fd);
 	if (fd == RT_NULL)
 	{
-		rt_set_errno(-RT_ERROR);
+		rt_set_errno(-DFS_STATUS_EBADF);
 		return -1;
 	}
 
@@ -633,11 +636,17 @@ int chdir(const char *path)
 	}
 
 	if (rt_strlen(path) > DFS_PATH_MAX)
+	{
+		rt_set_errno(-DFS_STATUS_ENOTDIR);
 		return -1;
+	}
 
 	fullpath = dfs_normalize_path(NULL, path);
 	if (fullpath == RT_NULL)
+	{
+		rt_set_errno(-DFS_STATUS_ENOTDIR);
 		return -1; /* build path failed */
+	}
 
 	dfs_lock();
 	d = opendir(fullpath);