bootmem: Add free_bootmem_late()

Add a new function for freeing bootmem after the bootmem
allocator has been released and the unreserved pages given to
the page allocator.

This allows us to reserve bootmem and then release it if we
later discover it was not needed.

( This new API will be used by the swiotlb code to recover
  a significant amount of RAM (64MB). )

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: chrisw@sous-sol.org
Cc: dwmw2@infradead.org
Cc: joerg.roedel@amd.com
Cc: muli@il.ibm.com
Cc: hannes@cmpxchg.org
Cc: tj@kernel.org
Cc: akpm@linux-foundation.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <1257849980-22640-7-git-send-email-fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 24 insertions, 0 deletions

diff --git a/mm/bootmem.c b/mm/bootmem.c
index 555d5d2731c6..d1dc23cc7f10 100644
--- a/mm/bootmem.c
+++ b/mm/bootmem.c
@@ -143,6 +143,30 @@ unsigned long __init init_bootmem(unsigned long start, unsigned long pages)
         return init_bootmem_core(NODE_DATA(0)->bdata, start, 0, pages);
 }
 
+/*
+ * free_bootmem_late - free bootmem pages directly to page allocator
+ * @addr: starting address of the range
+ * @size: size of the range in bytes
+ *
+ * This is only useful when the bootmem allocator has already been torn
+ * down, but we are still initializing the system.  Pages are given directly
+ * to the page allocator, no bootmem metadata is updated because it is gone.
+ */
+void __init free_bootmem_late(unsigned long addr, unsigned long size)
+{
+        unsigned long cursor, end;
+
+        kmemleak_free_part(__va(addr), size);
+
+        cursor = PFN_UP(addr);
+        end = PFN_DOWN(addr + size);
+
+        for (; cursor < end; cursor++) {
+                __free_pages_bootmem(pfn_to_page(cursor), 0);
+                totalram_pages++;
+        }
+}
+
 static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
 {
         int aligned;