[PATCH] zsmalloc: zspage sanity check

On Thu, Jun 02, 2016 at 09:25:19AM +0900, Minchan Kim wrote:

On Wed, Jun 01, 2016 at 04:09:26PM +0200, Vlastimil Babka wrote:

quoted

On 06/01/2016 01:21 AM, Minchan Kim wrote:

[...]

quoted

Cc: Sergey Senozhatsky <redacted>
Signed-off-by: Minchan Kim <minchan@kernel.org>

I'm not that familiar with zsmalloc, so this is not a full review. I was
just curious how it's handling the movable migration API, and stumbled
upon some things pointed out below.

quoted

@@ -252,16 +276,23 @@ struct zs_pool {
  */
 #define FULLNESS_BITS	2
 #define CLASS_BITS	8
+#define ISOLATED_BITS	3
+#define MAGIC_VAL_BITS	8
 
 struct zspage {
 	struct {
 		unsigned int fullness:FULLNESS_BITS;
 		unsigned int class:CLASS_BITS;
+		unsigned int isolated:ISOLATED_BITS;
+		unsigned int magic:MAGIC_VAL_BITS;

This magic seems to be only tested via VM_BUG_ON, so it's presence
should be also guarded by #ifdef DEBUG_VM, no?

Thanks for the point.

Then, I want to change it to BUG_ON because struct zspage corruption
is really risky to work rightly and want to catch on it in real product
which disable CONFIG_DEBUG_VM for a while until make the feature stable.

Andrew,

Please fold this patch into zsmalloc: page migration support.
Thanks!