On Thu, Mar 30 2006, Andrew Morton wrote:
> Jens Axboe <[email protected]> wrote:
> >
> > > The one-at-a-time logic looks OK from a quick scan. Do we have logic in
> > > there to check that we're not overrunning i_size? (See the pain
> > > do_generic_mapping_read() goes through).
> >
> > do_splice_to() checks that, should I move that checking further down in
> > case the file is truncated?
>
> Again, see do_generic_mapping_read()'s ghastly tricks - it checks i_size
> after each readpage().
>
> i_size can increase or decrease under our feet if we're not holding i_mutex
> (and we don't want to). So userspace is being silly and the main things we
> need to care about here are to not leak uninitialised data and to not oops.
> A readpage() outside i_size will return either all-zeroes or some valid
> data which isn't actually within i_size any more, so I guess we're OK.
So from the looks of things, worst case is returning zeroes if we
'raced' with someone truncating the file. I'll just leave it as-is for
now.
--
Jens Axboe
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