Re: [PATCH] xfs: reduce stack usage in xfs_bmap_btalloc()

Denys Vlasenko
2008-04-26T23:06:33Z

On Saturday 26 April 2008 20:54, Eric Sandeen wrote:
> > This patch reduces xfs_bmap_btalloc() stack usage by 50 bytes
> > by moving part of its body into a helper function.
> >
> > This results in some variables not taking stack space in
> > xfs_bmap_btalloc() anymore.
> >
> > The helper itself does not call anything stack-deep.
> > Stack-deep call to xfs_alloc_vextent() happen
> > in xfs_bmap_btalloc(), as before.
> >
> > Compile tested only.
> >
> > Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
>
> Looks like a very good approach, it pushes a lot of large local vars off
> into the helper.
>
> There is one build-time problem if DEBUG is turned on:
>
> if (args.fsbno != NULLFSBLOCK) {
> ap->firstblock = ap->rval = args.fsbno;
> ASSERT(nullfb || fb_agno == args.agno ||
> (ap->low && fb_agno < args.agno));
>
> in xfs_bmap_btalloc, which no longer has an fb_agno variable which the
> ASSERT macro uses.

Do you want me to rework and resend the patch?
--
vda