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mm/debug_pagealloc: ask users for default setting of debug_pagealloc

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Since commit 031bc5743f ("mm/debug-pagealloc: make debug-pagealloc
boottime configurable") CONFIG_DEBUG_PAGEALLOC is by default not adding
any page debugging.

This resulted in several unnoticed bugs, e.g.

    https://lkml.kernel.org/g/<569F5E29.3090107@de.ibm.com>
or
    https://lkml.kernel.org/g/<56A20F30.4050705@de.ibm.com>

as this behaviour change was not even documented in Kconfig.

Let's provide a new Kconfig symbol that allows to change the default
back to enabled, e.g.  for debug kernels.  This also makes the change
obvious to kernel packagers.

Let's also change the Kconfig description for CONFIG_DEBUG_PAGEALLOC, to
indicate that there are two stages of overhead.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Christian Borntraeger
2016-03-15 14:55:30 -07:00
committed by Linus Torvalds
parent d59b1087a9
commit ea6eabb05b
2 changed files with 21 additions and 3 deletions
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6
mm/page_alloc.c
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@@ -478,7 +478,8 @@ void prep_compound_page(struct page *page, unsigned int order)
#ifdef CONFIG_DEBUG_PAGEALLOC
unsigned int _debug_guardpage_minorder;
bool _debug_pagealloc_enabled __read_mostly;
bool _debug_pagealloc_enabled __read_mostly
= IS_ENABLED(CONFIG_DEBUG_PAGEALLOC_ENABLE_DEFAULT);
bool _debug_guardpage_enabled __read_mostly;
static int __init early_debug_pagealloc(char *buf)
@@ -489,6 +490,9 @@ static int __init early_debug_pagealloc(char *buf)
if (strcmp(buf, "on") == 0)
_debug_pagealloc_enabled = true;
if (strcmp(buf, "off") == 0)
_debug_pagealloc_enabled = false;
return 0;
}
early_param("debug_pagealloc", early_debug_pagealloc);