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

Denys Vlasenko wrote:
Hi David,

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@xxxxxxxxxxxxxx>
--
vda


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.

Thanks,

-Eric
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