On 2017-08-31 20:13, Qu Wenruo wrote:
On 2017年09月01日 01:27, Goffredo Baroncelli wrote:
Hi All,
I found a bug in mkfs.btrfs, when it is used the option '-r'. It seems
that it is not visible the full disk.
Despite the new bug you found, -r has several existing bugs.
Is this actually a bug though? Every other filesystem creation tool
that I know of that offers functionality like this generates the
filesystem just large enough to contain the data you want in it, so I
would argue that making this use the whole device is actually breaking
consistency with other tools, not to mention removing functionality that
is useful (even aside from the system image generation use case I
mentioned, there are other practical applications (seed 'device'
generation comes to mind).
For example it will create dev extent starting from physical offset 0,
while kernel and mkfs will avoid that range, as 0~1M on each device is
reserved.
According to the code, -r will modify chunk layout by itself, not the
traditional way kernel is doing.
I'll fix them (if I'm not a lazybone), before that fix, please don't use
-r option as it's not well maintained or fully tested.
FWIW, based on my own testing, filesystems generated with '-r' work just
fine as long as you don't try to embed boot code in the FS itself.
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