Query size of device using devpath rather than devname - also enables more logging on error #144
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The existing read_sys_block_size_bytes functions forces us to guess where to find a given device in the /sys/class/block hierarchy. While most of the time, /sys/class/block/<device>/size seems to be the right place to look, there have been reports of the file missing. We now provide another way to read the size using the DEVPATH udev variable instead. Hopefully, this should be a more accurate way to find the information we are looking for. Signed-off-by: Olivier Gayot <olivier.gayot@canonical.com>
Signed-off-by: Olivier Gayot <olivier.gayot@canonical.com>
If read_sys_devpath_size_bytes fails with ENOENT, we want to know whether it's the directory that does not exist of the file named "size". If the caller requests it, on error we now list the files contained in the /sys/<devpath> directory. If the directory does not exist, we will have a nested FileNotFoundError exception. Signed-off-by: Olivier Gayot <olivier.gayot@canonical.com>
This also enabled logging so we can figure out whether the directory or the file does not exist. Signed-off-by: Olivier Gayot <olivier.gayot@canonical.com>
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Looks like it requires #145 (or I can simply revisit the type hints to use Union) |
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Isn't it at least possible this is the race condition where udev processing a block device causes the device nodes for the devices partitions to disappear briefly? In that case I'd expect the devpath-based path to be missing too. Do we understand / remember why storage.py:blockdev_probe doesn't just look at the size attribute from udev? (it might give strange results for extended partitions perhaps?) |
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In LP:#2063433 and private reports associated to it, we observe that sometimes, accessing
/sys/class/block/<devname>/sizefails withFileNotFoundError.It isn't easy to determine whether the
sizefile does not exist or the parent directory itself.We now rely on a new way to retrieve the size, using the devpath instead of the devname. Hopefully, the devpath should always exist in sysfs if udev says so?
As for errors, we will now try to list the files from the parent directory when a
FileNotFoundExceptionis found as the result of the new function.