Hi David, On Tue, Jul 22, 2014 at 4:58 AM, David Rientjes <rientjes@xxxxxxxxxx> wrote: > On Thu, 17 Jul 2014, Max Filippov wrote: > >> From: Leonid Yegoshin <Leonid.Yegoshin@xxxxxxxxxx> >> >> Provide hooks that allow architectures with aliasing cache to align >> mapping address of high pages according to their color. Such architectures >> may enforce similar coloring of low- and high-memory page mappings and >> reuse existing cache management functions to support highmem. >> > > Typically a change like this would be proposed along with a change to an > architecture which would define this new ARCH_PKMAP_COLORING and have its > own overriding definitions. Based on who you sent this patch to, it looks > like that would be mips and xtensa. Now the only question is where are > those patches to add the alternate definitions for those platforms? I'm going to post xtensa series shortly, and I saw corresponding changes for MIPS in the following patch: http://permalink.gmane.org/gmane.linux.kernel.mm/107654 >> Signed-off-by: Leonid Yegoshin <Leonid.Yegoshin@xxxxxxxxxx> >> [ Max: extract architecture-independent part of the original patch, clean >> up checkpatch and build warnings. ] >> Signed-off-by: Max Filippov <jcmvbkbc@xxxxxxxxx> >> --- >> Changes v1->v2: >> - fix description >> >> mm/highmem.c | 19 ++++++++++++++++--- >> 1 file changed, 16 insertions(+), 3 deletions(-) >> >> diff --git a/mm/highmem.c b/mm/highmem.c >> index b32b70c..6898a8b 100644 >> --- a/mm/highmem.c >> +++ b/mm/highmem.c >> @@ -44,6 +44,14 @@ DEFINE_PER_CPU(int, __kmap_atomic_idx); >> */ >> #ifdef CONFIG_HIGHMEM >> >> +#ifndef ARCH_PKMAP_COLORING >> +#define set_pkmap_color(pg, cl) /* */ > > This is typically done with do {} while (0). Will fix. >> +#define get_last_pkmap_nr(p, cl) (p) >> +#define get_next_pkmap_nr(p, cl) (((p) + 1) & LAST_PKMAP_MASK) >> +#define is_no_more_pkmaps(p, cl) (!(p)) > > That's not gramatically proper. Just no_more_pkmaps maybe? >> +#define get_next_pkmap_counter(c, cl) ((c) - 1) >> +#endif >> + >> unsigned long totalhigh_pages __read_mostly; >> EXPORT_SYMBOL(totalhigh_pages); >> >> @@ -161,19 +169,24 @@ static inline unsigned long map_new_virtual(struct page *page) >> { >> unsigned long vaddr; >> int count; >> + int color __maybe_unused; >> + >> + set_pkmap_color(page, color); >> + last_pkmap_nr = get_last_pkmap_nr(last_pkmap_nr, color); >> >> start: >> count = LAST_PKMAP; >> /* Find an empty entry */ >> for (;;) { >> - last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK; >> - if (!last_pkmap_nr) { >> + last_pkmap_nr = get_next_pkmap_nr(last_pkmap_nr, color); >> + if (is_no_more_pkmaps(last_pkmap_nr, color)) { >> flush_all_zero_pkmaps(); >> count = LAST_PKMAP; >> } >> if (!pkmap_count[last_pkmap_nr]) >> break; /* Found a usable entry */ >> - if (--count) >> + count = get_next_pkmap_counter(count, color); > > And that's not equivalent at all, --count decrements the auto variable and > then tests it for being non-zero. Your get_next_pkmap_counter() never > decrements count. Yes, it's not literally equivalent, but it does the same thing: count gets decreased by 1 and for loop iterates until count reaches zero. get_next_pkmap_counter has no side effects, which is good. And count is not supposed to go below zero anyway, but sure I can change the below condition to 'if (count)'. >> + if (count > 0) >> continue; >> >> /* -- Thanks. -- Max
