From 74c08f982674cfd5dfeb2702d631db9bcdabf788 Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Mon, 8 Oct 2012 16:32:54 -0700 Subject: [PATCH] memory-hotplug: don't replace lowmem pages with highmem The changelog for commit 6a6dccba2fdc ("mm: cma: don't replace lowmem pages with highmem") mentioned that lowmem pages can be replaced by highmem pages during CMA migration. 6a6dccba2fdc 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: : [] (ext4_getblk+0x0/0x180) from [] (ext4_bread+0x1c/0x98) : [] (ext4_bread+0x0/0x98) from [] (ext4_mkdir+0x160/0x3bc) : r4:c15337f0 : [] (ext4_mkdir+0x0/0x3bc) from [] (vfs_mkdir+0x8c/0x98) : [] (vfs_mkdir+0x0/0x98) from [] (sys_mkdirat+0x74/0xac) : r6:00000000 r5:c152eb40 r4:000001ff r3:c14b43f0 : [] (sys_mkdirat+0x0/0xac) from [] (sys_mkdir+0x20/0x24) : r6:beccdcf0 r5:00074000 r4:beccdbbc : [] (sys_mkdir+0x0/0x24) from [] (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 Cc: Kamezawa Hiroyuki Reviewed-by: Yasuaki Ishimatsu Acked-by: Michal Nazarewicz Cc: Marek Szyprowski Cc: Wen Congyang Acked-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memory_hotplug.c | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-) 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); -- GitLab