From: zhong jiang <zhongjiang@xxxxxxxxxx> Subject: 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@xxxxxxxxxx Signed-off-by: zhong jiang <zhongjiang@xxxxxxxxxx> Suggested-by: Dan Streetman <ddstreet@xxxxxxxx> Acked-by: Dan Streetman <ddstreet@xxxxxxxx> Acked-by: Vitaly Wool <vitalywool@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/z3fold.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff -puN mm/z3fold.c~z3fold-limit-first_num-to-the-actual-range-of-possible-buddy-indexes mm/z3fold.c --- a/mm/z3fold.c~z3fold-limit-first_num-to-the-actual-range-of-possible-buddy-indexes +++ a/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_z 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); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
