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wic: do not ignore ROOTFS_SIZE if the rootfs is modified

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If the *.wks file contains a "--source rootfs" then
lib/wic/plugins/source/rootfs.py will be invoked to generate (what is assumed
to be) the rootfs partition. If the rootfs partition needs to be tweaked or
modified, the "rootfs.py" plugin will make a copy of the filesystem and then
perform the changes on that copy. In other words, if the "--source rootfs"
line of the *.wks file also contains any of:

	--exclude-path
	--include-path
	--change-directory
	--use-label (i.e. modify etc/fstab)

then the rootfs will be copied first, then the copy is modified.

If, for example, the unmodified IMAGE_ROOTFS is:

	.../tmp/work/qemuarm64_secureboot-oe-linux/core-image-base/1.0/rootfs

then the copy would be made at:

	.../tmp/work/qemuarm64_secureboot-oe-linux/core-image-base/1.0/tmp-wic/rootfs${LINENO}

where ${LINENO} is the line number where this "--source rootfs" line appears
in the *wks file.

When it comes time to make an actual partition of a specific filesystem type,
lib/wic/partition.py::prepare_rootfs() is called. It is in this function that
wic figures out if any extra size needs to be added. The bitbake variable used
to specify the ultimate rootfs size is ROOTFS_SIZE, and since this variable is
only valid for the rootfs (and not any other partitions), the code also
verifies that the partition being created is ${IMAGE_ROOTFS}:

	rsize_bb = get_bitbake_var('ROOTFS_SIZE')
	rdir = get_bitbake_var('IMAGE_ROOTFS')
	if rsize_bb and rdir == rootfs_dir:
		<use rsize_bb>
	else:
		<calculate the partition size using "du -ks $p">

As noted above, if lib/wic/plugins/source/rootfs.py has made a copy, then the
"rdir == rootfs_dir" clause will fail and the code will assume this partition
is not a rootfs since the strings do not compare equal.

Therefore, in order to determine if this is a rootfs, retain the existing
"rdir == rootfs_dir" comparison, but also add another one to check whether or
not this is a wic-generated copy of the rootfs.

STEPS TO REPRODUCE:
	- start with the following *wks file:
		bootloader --ptable gpt
		part /boot --size=100M --active --fstype=ext4 --label boot
		part /     --source rootfs      --fstype=ext4 --label root
	- and the following extra variable in conf/local.conf:
		IMAGE_ROOTFS_EXTRA_SPACE = "500000"
	- build an image
	- run it in qemu
		$ runqemu slirp nographic serial
	- verify the root partition has extra space:
		root@qemuarm64-secureboot:~# df -h
		Filesystem                Size      Used Available Use% Mounted on
		/dev/root               721.5M     67.4M    600.6M  10% /
		devtmpfs                477.7M         0    477.7M   0% /dev
		tmpfs                    40.0K         0     40.0K   0% /mnt
		tmpfs                   489.3M     92.0K    489.2M   0% /run
		tmpfs                   489.3M     68.0K    489.2M   0% /var/volatile
		/dev/vda1               120.4M     19.9M     91.4M  18% /boot
	- modify the "/" line of the *wks file to be:
		part /     --source rootfs      --fstype=ext4 --label root --exclude-path boot/
	- build image

	when it fails:
		root@qemuarm64-secureboot:~# df -h
		Filesystem                Size      Used Available Use% Mounted on
		/dev/root                73.4M     41.9M     25.8M  62% /
		devtmpfs                477.7M         0    477.7M   0% /dev
		tmpfs                    40.0K         0     40.0K   0% /mnt
		tmpfs                   489.3M     92.0K    489.2M   0% /run
		tmpfs                   489.3M     68.0K    489.2M   0% /var/volatile
		/dev/vda1               120.4M     19.9M     91.4M  18% /boot

	after this fix:
		root@qemuarm64-secureboot:~# df -h
		Filesystem                Size      Used Available Use% Mounted on
		/dev/root               721.5M     47.4M    620.6M   7% /
		devtmpfs                477.7M         0    477.7M   0% /dev
		tmpfs                    40.0K         0     40.0K   0% /mnt
		tmpfs                   489.3M     92.0K    489.2M   0% /run
		tmpfs                   489.3M     68.0K    489.2M   0% /var/volatile
		/dev/vda1               120.4M     19.9M     91.4M  18% /boot

Doing the math we see that the /boot partition is ~20MB and in the first image
the / partition contains this ~20MB in addition to the rest of the rootfs.
This ~20MB is completely wasted since it is used in the / partition, but then
the /boot partition is mounted on top of it, making the /boot directory of /
inaccessible. After the fix the / partition has an additional ~20MB since the
/boot portion is excluded.

Fixes [YOCTO #15555]

(From OE-Core rev: 1c690aa046ebca13d7b29de50d42b5d8a4a8486c)

Signed-off-by: Trevor Woerner <twoerner@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Trevor Woerner 2025-04-14 22:04:05 -04:00 committed by Richard Purdie
parent 94d2759dd7
commit 35807e8f63
2 changed files with 34 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
meta/lib/oeqa/selftest/cases/wic.py
View File

@ -535,6 +535,39 @@ part /mnt --source rootfs --ondisk mmcblk0 --fstype=ext4 --exclude-path bin/whoa
finally:
os.environ['PATH'] = oldpath
def test_exclude_path_with_extra_space(self):
"""Test having --exclude-path with IMAGE_ROOTFS_EXTRA_SPACE. [Yocto #15555]"""
with NamedTemporaryFile("w", suffix=".wks") as wks:
wks.writelines(
['bootloader --ptable gpt\n',
'part /boot --size=100M --active --fstype=ext4 --label boot\n',
'part / --source rootfs --fstype=ext4 --label root --exclude-path boot/\n'])
wks.flush()
config = 'IMAGE_ROOTFS_EXTRA_SPACE = "500000"\n'\
'DEPENDS:pn-core-image-minimal += "wic-tools"\n'\
'IMAGE_FSTYPES += "wic"\n'\
'WKS_FILE = "%s"\n' % wks.name
self.append_config(config)
bitbake('core-image-minimal')
"""
the output of "wic ls <image>.wic" will look something like:
Num Start End Size Fstype
1 17408 136332287 136314880 ext4
2 136332288 171464703 35132416 ext4
we are looking for the size of partition 2
i.e. in this case the number 35,132,416
without the fix the size will be around 85,403,648
with the fix the size should be around 799,960,064
"""
bb_vars = get_bb_vars(['DEPLOY_DIR_IMAGE', 'MACHINE'], 'core-image-minimal')
deploy_dir = bb_vars['DEPLOY_DIR_IMAGE']
machine = bb_vars['MACHINE']
wicout = glob(os.path.join(deploy_dir, "core-image-minimal-%s.rootfs-*.wic" % machine))[0]
size_of_root_partition = int(runCmd("wic ls %s" % wicout).output.split('\n')[2].split()[3])
self.assertGreater(size_of_root_partition, 500000000)
def test_include_path(self):
"""Test --include-path wks option."""

2
scripts/lib/wic/partition.py
View File

@ -244,7 +244,7 @@ class Partition():
# from bitbake variable
rsize_bb = get_bitbake_var('ROOTFS_SIZE')
rdir = get_bitbake_var('IMAGE_ROOTFS')
if rsize_bb and rdir == rootfs_dir:
if rsize_bb and (rdir == rootfs_dir or (rootfs_dir.split('/')[-2] == "tmp-wic" and rootfs_dir.split('/')[-1][:6] == "rootfs")):
# 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,