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authorVitaly Kuznetsov <vkuznets@redhat.com>2019-01-04 17:19:42 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-01-31 10:13:44 +0300
commita28dc8a5686a1641934f66b2a09c68a804810fe5 (patch)
treea05f477aa97c67c126a3b2260668ad02b5cc4a3b /drivers/hv
parentd9231608a7da07f115c55a3d05eca60bcf45f52b (diff)
downloadlinux-a28dc8a5686a1641934f66b2a09c68a804810fe5.tar.xz
hv_balloon: avoid touching uninitialized struct page during tail onlining
commit da8ced360ca8ad72d8f41f5c8fcd5b0e63e1555f upstream. Hyper-V memory hotplug protocol has 2M granularity and in Linux x86 we use 128M. To deal with it we implement partial section onlining by registering custom page onlining callback (hv_online_page()). Later, when more memory arrives we try to online the 'tail' (see hv_bring_pgs_online()). It was found that in some cases this 'tail' onlining causes issues: BUG: Bad page state in process kworker/0:2 pfn:109e3a page:ffffe08344278e80 count:0 mapcount:1 mapping:0000000000000000 index:0x0 flags: 0xfffff80000000() raw: 000fffff80000000 dead000000000100 dead000000000200 0000000000000000 raw: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 page dumped because: nonzero mapcount ... Workqueue: events hot_add_req [hv_balloon] Call Trace: dump_stack+0x5c/0x80 bad_page.cold.112+0x7f/0xb2 free_pcppages_bulk+0x4b8/0x690 free_unref_page+0x54/0x70 hv_page_online_one+0x5c/0x80 [hv_balloon] hot_add_req.cold.24+0x182/0x835 [hv_balloon] ... Turns out that we now have deferred struct page initialization for memory hotplug so e.g. memory_block_action() in drivers/base/memory.c does pages_correctly_probed() check and in that check it avoids inspecting struct pages and checks sections instead. But in Hyper-V balloon driver we do PageReserved(pfn_to_page()) check and this is now wrong. Switch to checking online_section_nr() instead. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: stable@kernel.org Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/hv')
-rw-r--r--drivers/hv/hv_balloon.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index db0e6652d7ef..0824405f93fb 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -846,12 +846,14 @@ static unsigned long handle_pg_range(unsigned long pg_start,
pfn_cnt -= pgs_ol;
/*
* Check if the corresponding memory block is already
- * online by checking its last previously backed page.
- * In case it is we need to bring rest (which was not
- * backed previously) online too.
+ * online. It is possible to observe struct pages still
+ * being uninitialized here so check section instead.
+ * In case the section is online we need to bring the
+ * rest of pfns (which were not backed previously)
+ * online too.
*/
if (start_pfn > has->start_pfn &&
- !PageReserved(pfn_to_page(start_pfn - 1)))
+ online_section_nr(pfn_to_section_nr(start_pfn)))
hv_bring_pgs_online(has, start_pfn, pgs_ol);
}