mm/zbud: reuse unbuddied[0] as buddied in zbud_pool

Patch series "Cleanups for zbud", v2.

This series contains just cleanups to save some possible memory in
zbud_pool and avoid exporting any unneeded zbud API.  More details can be
found in the respective changelogs

This patch (of 2):

Since commit 9d8c5b5284e4 ("mm: zbud: fix condition check on allocation
size"), zbud_pool.unbuddied[0] is always unused.  We can reuse it as
buddied field to save some possible memory.

Link: https://lkml.kernel.org/r/20210608114515.206992-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20210608114515.206992-2-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/zbud.c b/mm/zbud.c
index 7ec5f27..c48e60b 100644 (file)
--- a/mm/zbud.c
+++ b/mm/zbud.c
@@ -93,8 +93,14 @@
  */
 struct zbud_pool {
        spinlock_t lock;
-       struct list_head unbuddied[NCHUNKS];
-       struct list_head buddied;
+       union {
+               /*
+                * Reuse unbuddied[0] as buddied on the ground that
+                * unbuddied[0] is unused.
+                */
+               struct list_head buddied;
+               struct list_head unbuddied[NCHUNKS];
+       };
        struct list_head lru;
        u64 pages_nr;
        const struct zbud_ops *ops;