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SubjectRe: [PATCH] mm: cma: Discard clean pages during contiguous allocation instead of migration
On Thu, 13 Sep 2012 21:17:19 +0200
Geert Uytterhoeven <geert@linux-m68k.org> wrote:

> On Tue, Sep 11, 2012 at 2:41 AM, Minchan Kim <minchan@kernel.org> wrote:
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -674,8 +674,10 @@ static enum page_references page_check_references(struct page *page,
> > static unsigned long shrink_page_list(struct list_head *page_list,
> > struct zone *zone,
> > struct scan_control *sc,
> > + enum ttu_flags ttu_flags,
>
> "enum ttu_flags" is defined on CONFIG_MMU=y only, causing on nommu:
>
> mm/vmscan.c:677:26: error: parameter 4 ('ttu_flags') has incomplete type
> mm/vmscan.c:987:5: error: 'TTU_UNMAP' undeclared (first use in this function)
> mm/vmscan.c:987:15: error: 'TTU_IGNORE_ACCESS' undeclared (first use
> in this function)
> mm/vmscan.c:1312:56: error: 'TTU_UNMAP' undeclared (first use in this function)
>
> E.g.
> http://kisskb.ellerman.id.au/kisskb/buildresult/7191694/ (h8300-defconfig)
> http://kisskb.ellerman.id.au/kisskb/buildresult/7191858/ (sh-allnoconfig)

hm, OK, the means by which current mainline avoids build errors is
either clever or lucky.

switch (try_to_unmap(page, TTU_UNMAP)) {

gets preprocessed into

switch (2) {

so the cmopiler never gets to see the TTU_ symbol at all. Because it
happens to be inside the try_to_unmap() call.


I guess we can just make ttu_flags visible to NOMMU:


--- a/include/linux/rmap.h~mm-cma-discard-clean-pages-during-contiguous-allocation-instead-of-migration-fix-fix
+++ a/include/linux/rmap.h
@@ -71,6 +71,17 @@ struct anon_vma_chain {
#endif
};

+enum ttu_flags {
+ TTU_UNMAP = 0, /* unmap mode */
+ TTU_MIGRATION = 1, /* migration mode */
+ TTU_MUNLOCK = 2, /* munlock mode */
+ TTU_ACTION_MASK = 0xff,
+
+ TTU_IGNORE_MLOCK = (1 << 8), /* ignore mlock */
+ TTU_IGNORE_ACCESS = (1 << 9), /* don't age */
+ TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
+};
+
#ifdef CONFIG_MMU
static inline void get_anon_vma(struct anon_vma *anon_vma)
{
@@ -164,16 +175,6 @@ int page_referenced(struct page *, int i
int page_referenced_one(struct page *, struct vm_area_struct *,
unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);

-enum ttu_flags {
- TTU_UNMAP = 0, /* unmap mode */
- TTU_MIGRATION = 1, /* migration mode */
- TTU_MUNLOCK = 2, /* munlock mode */
- TTU_ACTION_MASK = 0xff,
-
- TTU_IGNORE_MLOCK = (1 << 8), /* ignore mlock */
- TTU_IGNORE_ACCESS = (1 << 9), /* don't age */
- TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
-};
#define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)

int try_to_unmap(struct page *, enum ttu_flags flags);
_


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