On 07/21/2014 05:58 PM, David Rientjes 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?
Yes, there is one, at least for MIPS. This stuff can be a common ground
for both platforms (MIPS and XTENSA)
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).
+#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.
+#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.
David, the statements
count = get_next_pkmap_counter(count, color);
if (count > 0)
are extended in STANDARD (non colored) case to
count = (count - 1);
if (count > 0)
which are perfect equivalent of
if (--count)
+ if (count > 0)
continue;
/*
