wic: obey the rootfs size from the metadata

When no --size is specified for the rootfs in the .wks, we want to obey the
rootfs size from the metadata, otherwise the defined IMAGE_ROOTFS_EXTRA_SPACE
and IMAGE_OVERHEAD_FACTOR will not be obeyed. In some cases, this can result
in image construction failure, if the size determined by du was insufficient
to hold the files without the aforementioned extra space.

This fallback from --size to ROOTFS_SIZE was already implemented when
--rootfs-dir is specified in the .wks, but it did not occur otherwise, neither
when --rootfs-dir= was passed to `wic create` nor when IMAGE_ROOTFS was used.
This made a certain amount of sense, as this fallback logic happened at such
a level that it wasn't able to identify which partitions were rootfs
partitions otherwise. Rather than doing it at that level, we can do it in
prepare_rootfs(), which is run by the rootfs source plugins.

Note that IMAGE_OVERHEAD_FACTOR and a --overhead-factor in the .wks will now
both be applied when --size isn't specified in the .wks. A warning is added
about this, though a user won't see it unless wic fails or they examine the
do_image_wic log.

Fixes [YOCTO #10815]

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>

1 files changed, 12 insertions, 1 deletions

diff --git a/scripts/lib/wic/partition.py b/scripts/lib/wic/partition.py
index ac4c836bdb..b191cdee54 100644
--- a/scripts/lib/wic/partition.py
+++ b/scripts/lib/wic/partition.py
@@ -28,7 +28,7 @@ import os
 import tempfile
 
 from wic.utils.oe.misc import msger, parse_sourceparams
-from wic.utils.oe.misc import exec_cmd, exec_native_cmd
+from wic.utils.oe.misc import exec_cmd, exec_native_cmd, get_bitbake_var
 from wic.plugin import pluginmgr
 
 partition_methods = {
@@ -194,6 +194,17 @@ class Partition():
             msger.error("File system for partition %s not specified in kickstart, " \
                         "use --fstype option" % (self.mountpoint))
 
+        # Get rootfs size from bitbake variable if it's not set in .ks file
+        if not self.size:
+            # Bitbake variable ROOTFS_SIZE is calculated in
+            # Image._get_rootfs_size method from meta/lib/oe/image.py
+            # using IMAGE_ROOTFS_SIZE, IMAGE_ROOTFS_ALIGNMENT,
+            # IMAGE_OVERHEAD_FACTOR and IMAGE_ROOTFS_EXTRA_SPACE
+            rsize_bb = get_bitbake_var('ROOTFS_SIZE')
+            if rsize_bb:
+                msger.warning('overhead-factor was specified, but size was not, so bitbake variables will be used for the size. In this case both IMAGE_OVERHEAD_FACTOR and --overhead-factor will be applied')
+                self.size = int(round(float(rsize_bb)))
+
         for prefix in ("ext", "btrfs", "vfat", "squashfs"):
             if self.fstype.startswith(prefix):
                 method = getattr(self, "prepare_rootfs_" + prefix)