Re: [PATCH 5/5] mm, memcontrol: use vma_is_anonymous() to check for anon VMA

Johannes Weiner wrote:

On Mon, Jul 13, 2015 at 01:54:12PM +0300, Kirill A. Shutemov wrote:

quoted

!vma->vm_file is not reliable to detect anon VMA, because not all
drivers bother set it. Let's use vma_is_anonymous() instead.

Signed-off-by: Kirill A. Shutemov <redacted>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <redacted>
---
 mm/memcontrol.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index acb93c554f6e..a624709f0dd7 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c

@@ -4809,7 +4809,7 @@ static struct page *mc_handle_file_pte(struct vm_area_struct *vma,
 	struct address_space *mapping;
 	pgoff_t pgoff;
 
-	if (!vma->vm_file) /* anonymous vma */
+	if (vma_is_anonymous(vma)) /* anonymous vma */
 		return NULL;
 	if (!(mc.flags & MOVE_FILE))
 		return NULL;

The next line does vma->vm_file->f_mapping, so it had better be !NULL.

It's not about reliably detecting anonymous vs. file, it is about
whether there is a mapping against which we can do find_get_page().

You're right. This patch is totally broken.

-- 
 Kirill

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