diff options
| author | Vitaly Kuznetsov <vkuznets@redhat.com> | 2019-01-04 15:19:42 +0100 |
|---|---|---|
| committer | Sasha Levin <sashal@kernel.org> | 2019-01-09 14:20:47 -0500 |
| commit | da8ced360ca8ad72d8f41f5c8fcd5b0e63e1555f (patch) | |
| tree | 0ed4f5ccc9d4200b8a9e4b91e6235ba002ec097b /drivers/hv/hv_balloon.c | |
| parent | ba50bf1ce9a51fc97db58b96d01306aa70bc3979 (diff) | |
| download | linux-da8ced360ca8ad72d8f41f5c8fcd5b0e63e1555f.tar.bz2 | |
hv_balloon: avoid touching uninitialized struct page during tail onlining
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>
Diffstat (limited to 'drivers/hv/hv_balloon.c')
| -rw-r--r-- | drivers/hv/hv_balloon.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c index 5301fef16c31..7c6349a50ef1 100644 --- a/drivers/hv/hv_balloon.c +++ b/drivers/hv/hv_balloon.c @@ -888,12 +888,14 @@ 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); } |