[OE-core] [PATCH v5 2/7] wic: copy rootfs directory before changing fstab

[Ed Bartosh]

wic updates /etc/fstab on root partition if there are
valid mount points in .wks

When wic runs from bitbake this can cause incorrect results
or even breakage of other tasks working with the same rootfs
directory in parallel with do_image_wic.

Implemented hardlinking rootfs directory to a temporary location
before updating fstab to avoid conflicts with other tasks working
with the same rootfs directory.

Signed-off-by: Ed Bartosh <ed.bartosh at linux.intel.com>
---
 scripts/lib/wic/plugins/imager/direct.py | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/scripts/lib/wic/plugins/imager/direct.py b/scripts/lib/wic/plugins/imager/direct.py
index f20d843..9b31c9e 100644
--- a/scripts/lib/wic/plugins/imager/direct.py
+++ b/scripts/lib/wic/plugins/imager/direct.py
@@ -115,12 +115,20 @@ class DirectPlugin(ImagerPlugin):
             fstab_lines = fstab.readlines()
 
         if self._update_fstab(fstab_lines, self.parts):
-            shutil.copyfile(fstab_path, fstab_path + ".orig")
+            # hardlink rootfs content to the temporary directory to update fstab
+            # as rootfs can be used by other tasks and can't be modified
+            new_rootfs = os.path.realpath(os.path.join(self.workdir, "rootfs_copy"))
+            exec_cmd("cp -al %s %s" % (image_rootfs, new_rootfs),
+                                       self.native_sysroot)
+
+            fstab_path = os.path.join(new_rootfs, 'etc/fstab')
+
+            os.unlink(fstab_path)
 
             with open(fstab_path, "w") as fstab:
                 fstab.writelines(fstab_lines)
 
-            return fstab_path
+            return new_rootfs
 
     def _update_fstab(self, fstab_lines, parts):
         """Assume partition order same as in wks"""
@@ -156,7 +164,10 @@ class DirectPlugin(ImagerPlugin):
         filesystems from the artifacts directly and combine them into
         a partitioned image.
         """
-        fstab_path = self._write_fstab(self.rootfs_dir.get("ROOTFS_DIR"))
+        new_rootfs = self._write_fstab(self.rootfs_dir.get("ROOTFS_DIR"))
+        if new_rootfs:
+            # rootfs was copied to update fstab
+            self.rootfs_dir['ROOTFS_DIR'] = new_rootfs
 
         for part in self.parts:
             # get rootfs size from bitbake variable if it's not set in .ks file
@@ -172,12 +183,7 @@ class DirectPlugin(ImagerPlugin):
                     if rsize_bb:
                         part.size = int(round(float(rsize_bb)))
 
-        try:
-            self._image.prepare(self)
-        finally:
-            if fstab_path:
-                shutil.move(fstab_path + ".orig", fstab_path)
-
+        self._image.prepare(self)
         self._image.layout_partitions()
         self._image.create()
 
-- 
2.1.4