mm, debug_pagealloc: use a page type instead of page_ext flag

[linux-2.6-microblaze.git] / mm / Kconfig.debug

diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index fa6d792..82b6a20 100644 (file)
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -12,19 +12,23 @@ config DEBUG_PAGEALLOC
        bool "Debug page memory allocations"
        depends on DEBUG_KERNEL
        depends on !HIBERNATION || ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC && !SPARC
-       select PAGE_EXTENSION
        select PAGE_POISONING if !ARCH_SUPPORTS_DEBUG_PAGEALLOC
        ---help---
          Unmap pages from the kernel linear mapping after free_pages().
          Depending on runtime enablement, this results in a small or large
          slowdown, but helps to find certain types of memory corruption.
 
+         Also, the state of page tracking structures is checked more often as
+         pages are being allocated and freed, as unexpected state changes
+         often happen for same reasons as memory corruption (e.g. double free,
+         use-after-free).
+
          For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC,
          fill the pages with poison patterns after free_pages() and verify
-         the patterns before alloc_pages().  Additionally,
-         this option cannot be enabled in combination with hibernation as
-         that would result in incorrect warnings of memory corruption after
-         a resume because free pages are not saved to the suspend image.
+         the patterns before alloc_pages(). Additionally, this option cannot
+         be enabled in combination with hibernation as that would result in
+         incorrect warnings of memory corruption after a resume because free
+         pages are not saved to the suspend image.
 
          By default this option will have a small overhead, e.g. by not
          allowing the kernel mapping to be backed by large pages on some