sys/vfs: provide vfs_fsync()

sys/include/vfs.h

@@ -440,6 +440,17 @@ struct vfs_file_ops {
      * @return <0 on error
      */
     ssize_t (*write) (vfs_file_t *filp, const void *src, size_t nbytes);
+
+    /**
+     * @brief Synchronize a file on storage
+     *        Any pending writes are written out to storage.
+     *
+     * @param[in]  filp     pointer to open file
+     *
+     * @return 0 on success
+     * @return <0 on error
+     */
+    int (*fsync) (vfs_file_t *filp);
 };
 
 /**
@@ -739,6 +750,17 @@ ssize_t vfs_read(int fd, void *dest, size_t count);
  */
 ssize_t vfs_write(int fd, const void *src, size_t count);
 
+/**
+ * @brief Synchronize a file on storage
+ *        Any pending writes are written out to storage.
+ *
+ * @param[in]  fd       fd number obtained from vfs_open
+ *
+ * @return 0 on success
+ * @return <0 on error
+ */
+int vfs_fsync(int fd);
+
 /**
  * @brief Open a directory for reading with readdir
  *

sys/vfs/vfs.c

@@ -333,6 +333,25 @@ ssize_t vfs_write(int fd, const void *src, size_t count)
     return filp->f_op->write(filp, src, count);
 }
 
+int vfs_fsync(int fd)
+{
+    DEBUG_NOT_STDOUT(fd, "vfs_fsync: %d\n", fd);
+    int res = _fd_is_valid(fd);
+    if (res < 0) {
+        return res;
+    }
+    vfs_file_t *filp = &_vfs_open_files[fd];
+    if (((filp->flags & O_ACCMODE) != O_WRONLY) & ((filp->flags & O_ACCMODE) != O_RDWR)) {
+        /* File not open for writing */
+        return -EBADF;
+    }
+    if (filp->f_op->fsync == NULL) {
+        /* driver does not implement fsync() */
+        return -EINVAL;
+    }
+    return filp->f_op->fsync(filp);
+}
+
 int vfs_opendir(vfs_DIR *dirp, const char *dirname)
 {
     DEBUG("vfs_opendir: %p, \"%s\"\n", (void *)dirp, dirname);