mirror of
https://github.com/hyperknot/openfreemap.git
synced 2026-05-21 14:02:15 +00:00
106 lines
3.2 KiB
Python
Executable File
106 lines
3.2 KiB
Python
Executable File
#!/usr/bin/env python3
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import os
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import subprocess
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import sys
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import tempfile
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from pathlib import Path
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import click
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# btrfs cannot shrink smaller than 256 MiB
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SMALLEST_SIZE = 256 * 1024 * 1024
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@click.command()
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@click.argument(
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'btrfs_img',
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type=click.Path(exists=True, dir_okay=False, file_okay=True, path_type=Path),
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)
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def cli(btrfs_img: Path):
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"""
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Shrinks a Btrfs image
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// I cannot believe that Btrfs is over 15 years old,
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// yet there is no resize2fs tool which can shrink a disk image
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// to minimum size.
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// It cannot even tell you how much should be the right size,
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// it just randomly fails after which you have to umount and mount again.
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// So we have to make a loop which tries to shrink it until it fails.
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// Also, WONTFIX bugs like how instead of telling you that
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// minimum fs size is 256 MB, it says "ERROR: unable to resize - Invalid argument"
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// https://bugzilla.kernel.org/show_bug.cgi?id=118111
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"""
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if os.geteuid() != 0:
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sys.exit(' needs sudo')
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current_dir = Path.cwd()
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mnt_dir = Path(tempfile.mkdtemp(dir=current_dir, prefix='tmp_shrink_'))
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subprocess.run(['mount', '-t', 'btrfs', btrfs_img, mnt_dir], check=True)
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# shink until max. 10 MB left or reached SMALLEST_SIZE or failure
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while True:
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# needs to start with a balancing
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# https://btrfs.readthedocs.io/en/latest/Balance.html
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# https://marc.merlins.org/perso/btrfs/post_2014-05-04_Fixing-Btrfs-Filesystem-Full-Problems.html
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do_balancing(mnt_dir)
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free_bytes = get_usage(mnt_dir, 'Device unallocated')
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device_size = get_usage(mnt_dir, 'Device size')
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shrink_idea = free_bytes * 0.7
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# workaround for the SMALLEST_SIZE limit
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if device_size - free_bytes < SMALLEST_SIZE:
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shrink_idea = (device_size - SMALLEST_SIZE) * 0.7
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# stop if 10 MB left
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if shrink_idea < 10_000_000:
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break
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# stop if process error
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if not do_shrink(mnt_dir, shrink_idea):
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break
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total_size = get_usage(mnt_dir, 'Device size')
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subprocess.run(['umount', mnt_dir])
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mnt_dir.rmdir()
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subprocess.run(['truncate', '-s', str(total_size), btrfs_img])
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print(f'Truncated {btrfs_img} to {total_size//1_000_000} MB size')
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print('shrink_btrfs.py DONE')
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def get_usage(mnt: Path, key: str):
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p = subprocess.run(
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['btrfs', 'filesystem', 'usage', '-b', mnt], text=True, capture_output=True, check=True
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)
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for line in p.stdout.splitlines():
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if f'{key}:' not in line:
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continue
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free = int(line.split(':')[1])
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return free
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def do_shrink(mnt: Path, delta_size: float):
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delta_size = int(delta_size)
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print(f'Trying to shrink by {delta_size//1_000_000} MB')
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p = subprocess.run(['btrfs', 'filesystem', 'resize', str(-delta_size), mnt])
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return p.returncode == 0
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def do_balancing(mnt: Path):
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print('Starting btrfs balancing')
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p = subprocess.run(
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['btrfs', 'balance', 'start', '-dusage=100', mnt], capture_output=True, text=True
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)
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if p.returncode:
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print(f'Balance error: {p.stdout} {p.stderr}')
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print('Balancing done')
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if __name__ == '__main__':
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cli()
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