Re: Partition device synchronisation

[Jeff Moyer <jmoyer@redhat.com>]

"Vladimir 'φ-coder/phcoder' Serbinenko" <phcoder@gmail.com> 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

Cheers,
Jeff
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