From: Minchan Kim <minchan@kernel.org>
Date: Thu, 13 Sep 2012 01:01:01 +0000 (+1000)
Subject: memory-hotplug: don't replace lowmem pages with highmem
X-Git-Tag: next-20120918~1^2~119
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=c98e0b8e9e9f1b0d3a78769114eb723e8fcdf441;p=karo-tx-linux.git

memory-hotplug: don't replace lowmem pages with highmem

The changelog for 6a6dccba2 ("mm: cma: don't replace lowmem pages with
highmem") mentioned that lowmem pages can be replaced by highmem pages
during CMA migration.  6a6dccba2 fixed that issue.

Quote from that changelog:

:   The filesystem layer expects pages in the block device's mapping to not
:   be in highmem (the mapping's gfp mask is set in bdget()), but CMA can
:   currently replace lowmem pages with highmem pages, leading to crashes in
:   filesystem code such as the one below:
:
:     Unable to handle kernel NULL pointer dereference at virtual address 00000400
:     pgd = c0c98000
:     [00000400] *pgd=00c91831, *pte=00000000, *ppte=00000000
:     Internal error: Oops: 817 [#1] PREEMPT SMP ARM
:     CPU: 0    Not tainted  (3.5.0-rc5+ #80)
:     PC is at __memzero+0x24/0x80
:     ...
:     Process fsstress (pid: 323, stack limit = 0xc0cbc2f0)
:     Backtrace:
:     [<c010e3f0>] (ext4_getblk+0x0/0x180) from [<c010e58c>] (ext4_bread+0x1c/0x98)
:     [<c010e570>] (ext4_bread+0x0/0x98) from [<c0117944>] (ext4_mkdir+0x160/0x3bc)
:      r4:c15337f0
:     [<c01177e4>] (ext4_mkdir+0x0/0x3bc) from [<c00c29e0>] (vfs_mkdir+0x8c/0x98)
:     [<c00c2954>] (vfs_mkdir+0x0/0x98) from [<c00c2a60>] (sys_mkdirat+0x74/0xac)
:      r6:00000000 r5:c152eb40 r4:000001ff r3:c14b43f0
:     [<c00c29ec>] (sys_mkdirat+0x0/0xac) from [<c00c2ab8>] (sys_mkdir+0x20/0x24)
:      r6:beccdcf0 r5:00074000 r4:beccdbbc
:     [<c00c2a98>] (sys_mkdir+0x0/0x24) from [<c000e3c0>] (ret_fast_syscall+0x0/0x30)

Memory-hotplug has same problem as CMA has so the same fix can be applied
to memory-hotplug as well.

Fix it by reusing.

Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index b35016156c19..f9ac0955e10a 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -756,13 +756,6 @@ static unsigned long scan_lru_pages(unsigned long start, unsigned long end)
 	return 0;
 }
 
-static struct page *
-hotremove_migrate_alloc(struct page *page, unsigned long private, int **x)
-{
-	/* This should be improooooved!! */
-	return alloc_page(GFP_HIGHUSER_MOVABLE);
-}
-
 #define NR_OFFLINE_AT_ONCE_PAGES	(256)
 static int
 do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
@@ -813,8 +806,12 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 			putback_lru_pages(&source);
 			goto out;
 		}
-		/* this function returns # of failed pages */
-		ret = migrate_pages(&source, hotremove_migrate_alloc, 0,
+
+		/*
+		 * alloc_migrate_target should be improooooved!!
+		 * migrate_pages returns # of failed pages.
+		 */
+		ret = migrate_pages(&source, alloc_migrate_target, 0,
 							true, MIGRATE_SYNC);
 		if (ret)
 			putback_lru_pages(&source);