page-writeback.c: subtract min_free_kbytes from dirtyable memory
When calculating amount of dirtyable memory, min_free_kbytes should be
subtracted because it is not intended for dirty pages.
Addresses http://bugs.debian.org/695182
[akpm@linux-foundation.org: fix up min_free_kbytes extern declarations]
[akpm@linux-foundation.org: fix min() warning]
Signed-off-by: Paul Szabo <psz@maths.usyd.edu.au>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 7300c9d..cdc377c 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -241,6 +241,9 @@
if (!vm_highmem_is_dirtyable)
x -= highmem_dirtyable_memory(x);
+ /* Subtract min_free_kbytes */
+ x -= min_t(unsigned long, x, min_free_kbytes >> (PAGE_SHIFT - 10));
+
return x + 1; /* Ensure that we never return 0 */
}