[066/192] mm/zbud: reuse unbuddied[0] as buddied in zbud_pool

Commit Message

Andrew Morton July 1, 2021, 1:50 a.m. UTC

From: Miaohe Lin <[e-mail]>
Subject: 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/[e-mail]
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Miaohe Lin <[e-mail]>
Cc: Seth Jennings <[e-mail]>
Cc: Dan Streetman <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/zbud.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

Patch

--- a/mm/zbud.c~mm-zbud-reuse-unbuddied-as-buddied-in-zbud_pool
+++ a/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;