RHEL7: System crash with NULL pointer at mirror_merge()

Issue

• System crash with NULL pointer at mirror_merge():

 #9 [ffff9022c33a3830] page_fault at ffffffff9518a778
    [exception RIP: unknown or invalid address]
    RIP: 0000000000000000  RSP: ffff9022c33a38e8  RFLAGS: 00010202
    RAX: 0000000000000000  RBX: ffff9022c33a3988  RCX: ffff90233f818340
    RDX: ffff905359789988  RSI: ffff9022c33a38f0  RDI: ffff9024023cc440
    RBP: ffff9022c33a3940   R8: 0000000000000000   R9: ffff902424b9d608
    R10: 0000000000000000  R11: ffff902424b9d608  R12: 0000000000000000
    R13: 0000000000010000  R14: ffff905359789988  R15: ffff902424b9e400
    ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
#10 [ffff9022c33a38e8] mirror_merge at ffffffffc030e155 [dm_mirror]
#11 [ffff9022c33a3948] dm_merge_bvec at ffffffffc02db847 [dm_mod]
#12 [ffff9022c33a3978] __bio_add_page at ffffffff94c8b71b
#13 [ffff9022c33a39e0] bio_add_page at ffffffff94c8b84d
#14 [ffff9022c33a39f0] do_mpage_readpage at ffffffff94c94310
#15 [ffff9022c33a3ac8] mpage_readpages at ffffffff94c94892
#16 [ffff9022c33a3ba8] blkdev_readpages at ffffffff94c8e55d
#17 [ffff9022c33a3bb8] __do_page_cache_readahead at ffffffff94bcb41f
#18 [ffff9022c33a3c78] force_page_cache_readahead at ffffffff94bcb969
#19 [ffff9022c33a3cb8] page_cache_sync_readahead at ffffffff94bcb9fb
#20 [ffff9022c33a3cc8] do_generic_file_read.constprop.52 at ffffffff94bbf12c
#21 [ffff9022c33a3d50] generic_file_aio_read at ffffffff94bbff09
#22 [ffff9022c33a3dd8] blkdev_aio_read at ffffffff94c8e96c
#23 [ffff9022c33a3e00] do_sync_read at ffffffff94c4d163
#24 [ffff9022c33a3ed8] vfs_read at ffffffff94c4db9f
#25 [ffff9022c33a3f08] sys_read at ffffffff94c4ea1f

• System getting crashed when doing pvmove migration.