On Tue, Jan 21, 2014 at 11:07 AM, Cai Liu [off-list ref] wrote:

Thanks for your review.

2014/1/21 Minchan Kim [off-list ref]:

quoted

Hello Cai,

On Mon, Jan 20, 2014 at 03:50:18PM +0800, Cai Liu wrote:

quoted

zswap can support multiple swapfiles. So we need to check
all zbud pool pages in zswap.

Version 2:
  * add *total_zbud_pages* in zbud to record all the pages in pools
  * move the updating of pool pages statistics to
    alloc_zbud_page/free_zbud_page to hide the details

Signed-off-by: Cai Liu <redacted>
---
 include/linux/zbud.h |    2 +-
 mm/zbud.c            |   44 ++++++++++++++++++++++++++++++++------------
 mm/zswap.c           |    4 ++--
 3 files changed, 35 insertions(+), 15 deletions(-)

diff --git a/include/linux/zbud.h b/include/linux/zbud.h
index 2571a5c..1dbc13e 100644
--- a/include/linux/zbud.h
+++ b/include/linux/zbud.h

@@ -17,6 +17,6 @@ void zbud_free(struct zbud_pool *pool, unsigned long handle);
 int zbud_reclaim_page(struct zbud_pool *pool, unsigned int retries);
 void *zbud_map(struct zbud_pool *pool, unsigned long handle);
 void zbud_unmap(struct zbud_pool *pool, unsigned long handle);
-u64 zbud_get_pool_size(struct zbud_pool *pool);
+u64 zbud_get_pool_size(void);

 #endif /* _ZBUD_H_ */

diff --git a/mm/zbud.c b/mm/zbud.c
index 9451361..711aaf4 100644
--- a/mm/zbud.c
+++ b/mm/zbud.c

@@ -52,6 +52,13 @@
 #include <linux/spinlock.h>
 #include <linux/zbud.h>

+/*********************************
+* statistics
+**********************************/
+
+/* zbud pages in all pools */
+static u64 total_zbud_pages;
+
 /*****************
  * Structures
 *****************/

@@ -142,10 +149,28 @@ static struct zbud_header *init_zbud_page(struct page *page)
      return zhdr;
 }

+static struct page *alloc_zbud_page(struct zbud_pool *pool, gfp_t gfp)
+{
+     struct page *page;
+
+     page = alloc_page(gfp);
+
+     if (page) {
+             pool->pages_nr++;
+             total_zbud_pages++;

Who protect race?

Yes, here the pool->pages_nr and also the total_zbud_pages are not protected.
I will re-do it.

I will change *total_zbud_pages* to atomic type.

And how about just add total_zbud_pages++ and leave pool->pages_nr in
its original place which already protected by pool->lock?

For *pool->pages_nr*, one way is to use pool->lock to protect. But I
think it is too heavy.
So does it ok to change pages_nr to atomic type too?

-- 
Regards,
--Bob

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