Re: [rfc][patch 2/2] buffer, btrfs: fix page_mkwrite error cases

[Chris Mason <chris.mason@oracle.com>]

On Tue, 2009-03-03 at 11:41 +0100, Nick Piggin wrote:
> page_mkwrite is called with neither the page lock nor the ptl held. This
> means a page can be concurrently truncated or invalidated out from underneath
> it. Callers are supposed to prevent truncate races themselves, however
> previously the only thing they can do in case they hit one is to raise a
> SIGBUS. A sigbus is wrong for the case that the page has been invalidated
> or truncated within i_size (eg. hole punched). Callers may also have to
> perform memory allocations in this path, where again, SIGBUS would be wrong.
> 
> The previous patch made it possible to properly specify errors. Convert
> the generic buffer.c code and btrfs to return sane error values
> (in the case of page removed from pagecache, VM_FAULT_NOPAGE will cause the
> fault handler to exit without doing anything, and the fault will be retried 
> properly).
> 

Thanks Nick.  I think the btrfs patch needs an extra } to compile, but
it looks fine.

-chris