Commit 74c08f98 authored Oct 08, 2012 by Minchan Kim Committed by Linus Torvalds Oct 09, 2012

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



The changelog for commit 6a6dccba ("mm: cma: don't replace lowmem
pages with highmem") mentioned that lowmem pages can be replaced by
highmem pages during CMA migration.  6a6dccba 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>
Reviewed-by: 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>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 723a0644

mm/memory_hotplug.c

+6 −9

Original line number	Diff line number	Diff line
		@@ -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);

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