StealthOS/subiquity
StealthOS
/
subiquity
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

beef up comments

This commit is contained in:
Michael Hudson-Doyle 2019-11-08 09:31:49 +13:00
parent fde1c53141
commit d532648794
1 changed files with 19 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
subiquity/models/filesystem.py
View File

@ -221,18 +221,24 @@ def dehumanize_size(size):
DEFAULT_CHUNK = 512 DEFAULT_CHUNK = 512
# The calculation of how much of a device mdadm uses for raid is more than a
# touch ridiculous. What follows is a translation of the code at:
# https://git.kernel.org/pub/scm/utils/mdadm/mdadm.git/tree/super1.c,
# specifically choose_bm_space and the end of validate_geometry1. Note that
# that calculations are in terms of 512-byte sectors.
#
# We make some assumptions about the defaults mdadm uses but mostly that the
# default metadata version is 1.2, and other formats use less space.
#
# Note that data_offset is computed for the first disk mdadm examines and then
# used for all devices, so the order matters! (Well, if the size of the
# devices vary, which is not normal but also not something we prevent).
#
# All this is tested against reality in ./scripts/get-raid-sizes.py
def calculate_data_offset(devsize): def calculate_data_offset(devsize):
devsize >>= 9 # convert to sectors devsize >>= 9 # convert to sectors
devsize = align_down(devsize, DEFAULT_CHUNK) devsize = align_down(devsize, DEFAULT_CHUNK)
# The calculation of how much of a device mdadm uses for raid is a
# touch ridiculous. What follows is a translation of the code at:
# https://git.kernel.org/pub/scm/utils/mdadm/mdadm.git/tree/super1.c?h=mdadm-4.1&id=20e8fe52e7190b3ffda127566852eac2eb7fa1f7#n2770
# (note that that calculations are in terms of 512-byte sectors).
#
# This makes assumptions about the defaults mdadm uses but mostly
# that the default metadata version is 1.2, and other formats use
# less space.
# conversion of choose_bm_space: # conversion of choose_bm_space:
if devsize < 64*2: if devsize < 64*2:
@ -244,6 +250,7 @@ def calculate_data_offset(devsize):
else: else:
bmspace = 4*2 bmspace = 4*2
# From the end of validate_geometry1, assuming metadata 1.2.
headroom = 128*1024*2 headroom = 128*1024*2
while (headroom << 10) > devsize and headroom / 2 >= DEFAULT_CHUNK*2*2: while (headroom << 10) > devsize and headroom / 2 >= DEFAULT_CHUNK*2*2:
headroom >>= 1 headroom >>= 1
@ -259,10 +266,13 @@ def calculate_data_offset(devsize):
def raid_device_sort(devices): def raid_device_sort(devices):
# Because the device order matters to mdadm, we sort consistently but
# arbitrarily when computing the size and when rendering the config (so
# curtin passes the devices to mdadm in the order we calculate the size
# for)
return sorted(devices, key=lambda d: d.id) return sorted(devices, key=lambda d: d.id)
# This this is tested against reality in ./scripts/get-raid-sizes.py
def get_raid_size(level, devices): def get_raid_size(level, devices):
if len(devices) == 0: if len(devices) == 0:
return 0 return 0