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authorzhong jiang <zhongjiang@huawei.com>2017-02-22 15:46:51 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-02-22 16:41:31 -0800
commitf201ebd87652cf1519792f8662bb3f862c76aa33 (patch)
tree3dfc4774407bcc51d5cb91066af04cdc7eb8d3b8
parent083fb8edda0487d192e8c117f625563b920cf7a4 (diff)
mm/z3fold.c: limit first_num to the actual range of possible buddy indexes
At present, Tying the first_num size to NCHUNKS_ORDER is confusing. the number of chunks is completely unrelated to the number of buddies. The patch limits the first_num to actual range of possible buddy indexes. and that is more reasonable and obvious without functional change. Link: http://lkml.kernel.org/r/1476776569-29504-1-git-send-email-zhongjiang@huawei.com Signed-off-by: zhong jiang <zhongjiang@huawei.com> Suggested-by: Dan Streetman <ddstreet@ieee.org> Acked-by: Dan Streetman <ddstreet@ieee.org> Acked-by: Vitaly Wool <vitalywool@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/z3fold.c10
1 files changed, 7 insertions, 3 deletions
diff --git a/mm/z3fold.c b/mm/z3fold.c
index 8f9e89ca1d31..207e5ddc87a2 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -50,7 +50,7 @@
#define ZHDR_SIZE_ALIGNED CHUNK_SIZE
#define NCHUNKS ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT)
-#define BUDDY_MASK ((1 << NCHUNKS_ORDER) - 1)
+#define BUDDY_MASK (0x3)
struct z3fold_pool;
struct z3fold_ops {
@@ -109,7 +109,7 @@ struct z3fold_header {
unsigned short middle_chunks;
unsigned short last_chunks;
unsigned short start_middle;
- unsigned short first_num:NCHUNKS_ORDER;
+ unsigned short first_num:2;
};
/*
@@ -179,7 +179,11 @@ static struct z3fold_header *handle_to_z3fold_header(unsigned long handle)
return (struct z3fold_header *)(handle & PAGE_MASK);
}
-/* Returns buddy number */
+/*
+ * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
+ * but that doesn't matter. because the masking will result in the
+ * correct buddy number.
+ */
static enum buddy handle_to_buddy(unsigned long handle)
{
struct z3fold_header *zhdr = handle_to_z3fold_header(handle);