3.16.61-rc1 review patch. If anyone has any objections, please let me know.
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From: Jiang Biao jiang.biao2@zte.com.cn
commit 89da619bc18d79bca5304724c11d4ba3b67ce2c6 upstream.
Kernel panic when with high memory pressure, calltrace looks like,
PID: 21439 TASK: ffff881be3afedd0 CPU: 16 COMMAND: "java" #0 [ffff881ec7ed7630] machine_kexec at ffffffff81059beb #1 [ffff881ec7ed7690] __crash_kexec at ffffffff81105942 #2 [ffff881ec7ed7760] crash_kexec at ffffffff81105a30 #3 [ffff881ec7ed7778] oops_end at ffffffff816902c8 #4 [ffff881ec7ed77a0] no_context at ffffffff8167ff46 #5 [ffff881ec7ed77f0] __bad_area_nosemaphore at ffffffff8167ffdc #6 [ffff881ec7ed7838] __node_set at ffffffff81680300 #7 [ffff881ec7ed7860] __do_page_fault at ffffffff8169320f #8 [ffff881ec7ed78c0] do_page_fault at ffffffff816932b5 #9 [ffff881ec7ed78f0] page_fault at ffffffff8168f4c8 [exception RIP: _raw_spin_lock_irqsave+47] RIP: ffffffff8168edef RSP: ffff881ec7ed79a8 RFLAGS: 00010046 RAX: 0000000000000246 RBX: ffffea0019740d00 RCX: ffff881ec7ed7fd8 RDX: 0000000000020000 RSI: 0000000000000016 RDI: 0000000000000008 RBP: ffff881ec7ed79a8 R8: 0000000000000246 R9: 000000000001a098 R10: ffff88107ffda000 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000008 R14: ffff881ec7ed7a80 R15: ffff881be3afedd0 ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
It happens in the pagefault and results in double pagefault during compacting pages when memory allocation fails.
Analysed the vmcore, the page leads to second pagefault is corrupted with _mapcount=-256, but private=0.
It's caused by the race between migration and ballooning, and lock missing in virtballoon_migratepage() of virtio_balloon driver. This patch fix the bug.
Fixes: e22504296d4f64f ("virtio_balloon: introduce migration primitives to balloon pages") Signed-off-by: Jiang Biao jiang.biao2@zte.com.cn Signed-off-by: Huang Chong huang.chong@zte.com.cn Signed-off-by: Michael S. Tsirkin mst@redhat.com Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/virtio/virtio_balloon.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -413,7 +413,9 @@ static int virtballoon_migratepage(struc tell_host(vb, vb->inflate_vq);
/* balloon's page migration 2nd step -- deflate "page" */ + spin_lock_irqsave(&vb_dev_info->pages_lock, flags); balloon_page_delete(page); + spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags); vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; set_page_pfns(vb->pfns, page); tell_host(vb, vb->deflate_vq);