Hi Al, David,

vfs function write_cache_pages() appears on the xfs
writeout path. It's *the* path which causes 4k stack
overflows on i386 with xfs.

This function uses ~100 bytes of stack on 32-bit i386.

This patch transforms it a little so that it uses
a bit less stack - minus 8 bytes to be precise.

This isn't much, but it helps not only xfs,
but all filesystems.

Only compile tested.

Signed-off-by: Denys Vlasenko