[PATCH v2] z3fold: fix the potential encode bug in encod_handle

[zhongjiang]

From: zhong jiang <zhongji...@huawei.com>

At present, zhdr->first_num plus bud can exceed the BUDDY_MASK
in encode_handle, it will lead to the the caller handle_to_buddy
return the error value.

The patch fix the issue by changing the BUDDY_MASK to PAGE_MASK,
it will be consistent with handle_to_z3fold_header. At the same time,
change the BUDDY_MASK to PAGE_MASK in handle_to_buddy is better.

Signed-off-by: zhong jiang <zhongji...@huawei.com>
---
 mm/z3fold.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/z3fold.c b/mm/z3fold.c
index 8f9e89c..e8fc216 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -169,7 +169,7 @@ static unsigned long encode_handle(struct z3fold_header 
*zhdr, enum buddy bud)
 
        handle = (unsigned long)zhdr;
        if (bud != HEADLESS)
-               handle += (bud + zhdr->first_num) & BUDDY_MASK;
+               handle += (bud + zhdr->first_num) & PAGE_MASK;
        return handle;
 }
 
@@ -183,7 +183,7 @@ static struct z3fold_header 
*handle_to_z3fold_header(unsigned long handle)
 static enum buddy handle_to_buddy(unsigned long handle)
 {
        struct z3fold_header *zhdr = handle_to_z3fold_header(handle);
-       return (handle - zhdr->first_num) & BUDDY_MASK;
+       return (handle - zhdr->first_num) & PAGE_MASK;
 }
 
 /*
-- 
1.8.3.1