zsmalloc: zspage sanity check

Quoted 19 lines · Vlastimil Babka

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

[...]

Quoted 3 lines

Cc Sergey Senozhatsky <[email protected]>

Signed-off-by Minchan Kim <[email protected]>

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.

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@@ -252,16 +276,23 @@ struct zs_pool {
  */
 #define FULLNESS_BITS	2
 #define CLASS_BITS	8
+#define ISOLATED_BITS	3
+#define MAGIC_VAL_BITS	8
 

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Review struct zs_pool { · line 287

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 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.