mm: enhance free_reserved_area() to support poisoning memory with zero

Address more review comments from last round of code review.
1) Enhance free_reserved_area() to support poisoning freed memory with
   pattern '0'. This could be used to get rid of poison_init_mem()
   on ARM64.
2) A previous patch has disabled memory poison for initmem on s390
   by mistake, so restore to the original behavior.
3) Remove redundant PAGE_ALIGN() when calling free_reserved_area().

Signed-off-by: Jiang Liu <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: "Michael S. Tsirkin" <[email protected]>
Cc: <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Chris Metcalf <[email protected]>
Cc: David Howells <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jeremy Fitzhardinge <[email protected]>
Cc: Jianguo Wu <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Kamezawa Hiroyuki <[email protected]>
Cc: Konrad Rzeszutek Wilk <[email protected]>
Cc: Marek Szyprowski <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Michel Lespinasse <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Rusty Russell <[email protected]>
Cc: Tang Chen <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Wen Congyang <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Yasuaki Ishimatsu <[email protected]>
Cc: Yinghai Lu <[email protected]>
Cc: Russell King <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 4 insertions, 3 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index be1b96ce0650..083cc0ba2384 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1308,7 +1308,7 @@ extern void free_initmem(void);
 /*
  * Free reserved pages within range [PAGE_ALIGN(start), end & PAGE_MASK)
  * into the buddy system. The freed pages will be poisoned with pattern
- * "poison" if it's non-zero.
+ * "poison" if it's within range [0, UCHAR_MAX].
  * Return pages freed into the buddy system.
  */
 extern unsigned long free_reserved_area(void *start, void *end,
@@ -1348,8 +1348,9 @@ static inline void mark_page_reserved(struct page *page)
 
 /*
  * Default method to free all the __init memory into the buddy system.
- * The freed pages will be poisoned with pattern "poison" if it is
- * non-zero. Return pages freed into the buddy system.
+ * The freed pages will be poisoned with pattern "poison" if it's within
+ * range [0, UCHAR_MAX].
+ * Return pages freed into the buddy system.
  */
 static inline unsigned long free_initmem_default(int poison)
 {