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authorPaul Mackerras <paulus@samba.org>2013-08-05 14:11:23 +1000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2013-08-14 14:57:14 +1000
commit1f7bf028763cacf5a5674731e8f679c4718f2cfa (patch)
treede9250e864122d35d184dcb84d30f59f08631b1a /arch
parentcb96143defbd5516c351595d56b608ed915b525e (diff)
downloadlinux-stericsson-1f7bf028763cacf5a5674731e8f679c4718f2cfa.tar.gz
powerpc: Implement __get_user_pages_fast()
Other architectures have a __get_user_pages_fast(), in addition to the regular get_user_pages_fast(), which doesn't call get_user_pages() on failure, and thus doesn't attempt to fault pages in or COW them. The generic KVM code uses __get_user_pages_fast() to detect whether a page for which we have only requested read access is actually writable. This provides an implementation of __get_user_pages_fast() by splitting the existing get_user_pages_fast() in two. With this, the generic KVM code will get the right answer instead of always considering such pages non-writable. Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/mm/gup.c37
1 files changed, 21 insertions, 16 deletions
diff --git a/arch/powerpc/mm/gup.c b/arch/powerpc/mm/gup.c
index 49822d90ea96..6936547018b8 100644
--- a/arch/powerpc/mm/gup.c
+++ b/arch/powerpc/mm/gup.c
@@ -117,8 +117,8 @@ static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end,
return 1;
}
-int get_user_pages_fast(unsigned long start, int nr_pages, int write,
- struct page **pages)
+int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
+ struct page **pages)
{
struct mm_struct *mm = current->mm;
unsigned long addr, len, end;
@@ -135,7 +135,7 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write,
if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
start, len)))
- goto slow_irqon;
+ return 0;
pr_devel(" aligned: %lx .. %lx\n", start, end);
@@ -166,30 +166,35 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write,
(void *)pgd_val(pgd));
next = pgd_addr_end(addr, end);
if (pgd_none(pgd))
- goto slow;
+ break;
if (pgd_huge(pgd)) {
if (!gup_hugepte((pte_t *)pgdp, PGDIR_SIZE, addr, next,
write, pages, &nr))
- goto slow;
+ break;
} else if (is_hugepd(pgdp)) {
if (!gup_hugepd((hugepd_t *)pgdp, PGDIR_SHIFT,
addr, next, write, pages, &nr))
- goto slow;
+ break;
} else if (!gup_pud_range(pgd, addr, next, write, pages, &nr))
- goto slow;
+ break;
} while (pgdp++, addr = next, addr != end);
local_irq_enable();
- VM_BUG_ON(nr != (end - start) >> PAGE_SHIFT);
return nr;
+}
- {
- int ret;
+int get_user_pages_fast(unsigned long start, int nr_pages, int write,
+ struct page **pages)
+{
+ struct mm_struct *mm = current->mm;
+ int nr, ret;
+
+ start &= PAGE_MASK;
+ nr = __get_user_pages_fast(start, nr_pages, write, pages);
+ ret = nr;
-slow:
- local_irq_enable();
-slow_irqon:
+ if (nr < nr_pages) {
pr_devel(" slow path ! nr = %d\n", nr);
/* Try to get the remaining pages with get_user_pages */
@@ -198,7 +203,7 @@ slow_irqon:
down_read(&mm->mmap_sem);
ret = get_user_pages(current, mm, start,
- (end - start) >> PAGE_SHIFT, write, 0, pages, NULL);
+ nr_pages - nr, write, 0, pages, NULL);
up_read(&mm->mmap_sem);
/* Have to be a bit careful with return values */
@@ -208,9 +213,9 @@ slow_irqon:
else
ret += nr;
}
-
- return ret;
}
+
+ return ret;
}
#endif /* __HAVE_ARCH_PTE_SPECIAL */