Hi Matthew,
On Fri, Apr 17, 2020 at 12:01 AM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
PageWaiters is used by PageWriteback and PageLocked (and no other page
flags), so it makes sense to use the same codepaths that have already been
optimised for PageLocked, even if there's probably no real performance
benefit to be had.
Unfortunately, clear_bit_unlock_is_negative_byte() isn't present on every
architecture, and the default implementation is only available in filemap.c
while I want to use it in page-writeback.c. Rather than move the default
implementation to a header file, I've done optimised implementations for
alpha and ia64. I can't figure out optimised implementations for m68k,
mips, riscv and s390, so I've just replicated the effect of the generic
implementation in them. I leave it to the experts to fix that (... or
convert over to using asm-generic/bitops/lock.h ...)
v3:
- Added implementations of clear_bit_unlock_is_negative_byte()
to architectures which need it
I have two questions here?
1. Why not implement arch_clear_bit_unlock_is_negative_byte()
instead, so the kasan check in asm-generic is used everywhere?
2. Why not add the default implementation to
include/asm-generic/bitops/instrumented-lock.h, in case an arch_*()
variant is not provided yet?
Note that you did 1 for s390.
Thanks!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
