Re: Partition device synchronisation

[Vladimir 'φ-coder/phcoder' Serbinenko <phcoder@xxxxxxxxx>]

On 11.05.2012 15:39, Jeff Moyer wrote:
> "Vladimir 'φ-coder/phcoder' Serbinenko" <phcoder@xxxxxxxxx> writes:
>
>> Hello, all. In GRUB we have tools to discover various parameters as to
>> how GRUB would see the disks on boot and for this we run the same code
>> as we have in boot time in userspace. So most natural for us would be
>> accessing whole disks like sda but unfortunately its cache isn't kept
>> synchronous with partitions (e.g. sda1), so if FS driver writes
>> something to sda1 it won't be visible through sda until pages are
>> dropped. Right now in Linux-specific code we try to find which partition
>> of sda starts at given sector (e.g. 2048) by trying all partition Linux
>> sees in order to read from sda1 rather than sda. The code is ugly and
>> sometimes create issues. So my questions are:
>> 1) Do we have to issue some ioctl to reload those caches?
> You can issue the BLKFLSBUF ioctl.
>
>> 2) Is it considered a bug and should I plunge forward, fix it and send a
>> patch?
> This is debatable.  See this thread:
>   http://thread.gmane.org/gmane.linux.kernel/1241227/focus=1244202
Thank you, it's all clear to me now. I'll make a patch based on this
information and ask the affected user to test it.
> Cheers,
> Jeff
>


-- 
Regards
Vladimir 'φ-coder/phcoder' Serbinenko

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