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Commit f201ebd8 authored by zhong jiang's avatar zhong jiang Committed by Linus Torvalds
Browse files

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: default avatarzhong jiang <zhongjiang@huawei.com>
Suggested-by: default avatarDan Streetman <ddstreet@ieee.org>
Acked-by: default avatarDan Streetman <ddstreet@ieee.org>
Acked-by: default avatarVitaly Wool <vitalywool@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 083fb8ed

mm/z3fold.c

+7 −3
Original line number Diff line number Diff line
@@ -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);