[PATCH] mm: follow_page with inner ptlock
Final step in pushing down common core's page_table_lock. follow_page no
longer wants caller to hold page_table_lock, uses pte_offset_map_lock itself;
and so no page_table_lock is taken in get_user_pages itself.
But get_user_pages (and get_futex_key) do then need follow_page to pin the
page for them: take Daniel's suggestion of bitflags to follow_page.
Need one for WRITE, another for TOUCH (it was the accessed flag before:
vanished along with check_user_page_readable, but surely get_numa_maps is
wrong to mark every page it finds as accessed), another for GET.
And another, ANON to dispose of untouched_anonymous_page: it seems silly for
that to descend a second time, let follow_page observe if there was no page
table and return ZERO_PAGE if so. Fix minor bug in that: check VM_LOCKED -
make_pages_present ought to make readonly anonymous present.
Give get_numa_maps a cond_resched while we're there.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/linux/mm.h b/include/linux/mm.h
index aa8de20..e8d1424 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -938,14 +938,18 @@
return (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
}
-extern struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr);
+struct vm_area_struct *find_extend_vma(struct mm_struct *, unsigned long addr);
+struct page *vmalloc_to_page(void *addr);
+unsigned long vmalloc_to_pfn(void *addr);
+int remap_pfn_range(struct vm_area_struct *, unsigned long addr,
+ unsigned long pfn, unsigned long size, pgprot_t);
-extern struct page * vmalloc_to_page(void *addr);
-extern unsigned long vmalloc_to_pfn(void *addr);
-extern struct page * follow_page(struct mm_struct *mm, unsigned long address,
- int write);
-int remap_pfn_range(struct vm_area_struct *, unsigned long,
- unsigned long, unsigned long, pgprot_t);
+struct page *follow_page(struct mm_struct *, unsigned long address,
+ unsigned int foll_flags);
+#define FOLL_WRITE 0x01 /* check pte is writable */
+#define FOLL_TOUCH 0x02 /* mark page accessed */
+#define FOLL_GET 0x04 /* do get_page on page */
+#define FOLL_ANON 0x08 /* give ZERO_PAGE if no pgtable */
#ifdef CONFIG_PROC_FS
void vm_stat_account(struct mm_struct *, unsigned long, struct file *, long);