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btrfs hack: shrink the allocated size

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We are using read-only btrfs compressed for the /usr partition,
and sometimes the free space shown by `btrfs fi usage` and the `df` IS diverging,
with `df` showing the free space from the `btrfs fi usage`'s `Device unallocated.

I have found a way to fix the allocation, by decreasing the size to more than the btrfs
filesystem allows, but curiosly the allocation is getting reset during the failed
attempt and the issue is fixed.

This is of course, a _HACK_, and can at any time produce unwanted behaviours.

Note that the issue cannot be reliably reproduced.

See Flatcar issue: https://github.com/flatcar/Flatcar/issues/1473

See issue upstream:
https://bugzilla.kernel.org/show_bug.cgi?id=219167

Signed-off-by: Adrian Vladu <avladu@cloudbasesolutions.com>
This commit is contained in:
Adrian Vladu 2024-09-05 15:55:36 +03:00
parent a2598effed
commit 51d5509c83
2 changed files with 25 additions and 0 deletions
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2
build_library/build_image_util.sh
View File

@ -806,6 +806,8 @@ EOF
sudo fstrim "${root_fs_dir}/usr" || true
fi
"${BUILD_LIBRARY_DIR}/disk_util" --disk_layout="${disk_layout}" btrfsresetallocation \
"${root_fs_dir}/usr"
# Make the filesystem un-mountable as read-write and setup verity.
if [[ ${disable_read_write} -eq ${FLAGS_TRUE} ]]; then
# Unmount /usr partition

23
build_library/disk_util
View File

@ -768,6 +768,25 @@ def Tune(options):
if not action_done:
raise Exception("No options specified!")
def SudoOutputToConsole(cmd):
print(SudoOutput(cmd).decode())
def LogBtrfsUsage(mount_point, section=None):
print('Btrfs usage for mount point `%s` %s' % (mount_point, section))
try:
SudoOutputToConsole(['btrfs', 'fi', 'usage', mount_point])
except Exception as ex:
print('Btrfs usage could not be retrieved for mount point `%s` %s' % (mount_point, section))
print(ex)
def BtrfsResetAllocation(options):
LogBtrfsUsage(options.disk_image, 'before disk resize')
try:
Sudo(['btrfs', 'fi', 'resize', '-500m', options.disk_image])
except Exception as ex:
print(ex)
LogBtrfsUsage(options.disk_image, 'after disk resize')
def Verity(options):
"""Hash verity protected filesystems.
@ -1119,6 +1138,10 @@ def main(argv):
a = actions.add_parser('parseonly', help='validate config')
a.set_defaults(func=DoParseOnly)
a = actions.add_parser('btrfsresetallocation', help='btrfs reset allocation')
a.add_argument('disk_image', help='path to disk image file')
a.set_defaults(func=BtrfsResetAllocation)
options = parser.parse_args(argv[1:])
options.func(options)