Comment 0 for bug 1566518

On 2 socket ThunderX systems, a BUG() is triggered by the ext4 filesystem shortly after boot:

[ 230.637307] Call trace:
[ 230.641753] [<ffff8000002eac90>] mpage_prepare_extent_to_map+0x270/0x290
[ 230.650515] [<ffff8000002eefe0>] ext4_writepages+0x3b0/0xc10
[ 230.658259] [<ffff8000001dcd88>] do_writepages+0x40/0x70
[ 230.665639] [<ffff800000287988>] __writeback_single_inode+0x48/0x3c8
[ 230.674071] [<ffff800000288200>] writeback_sb_inodes+0x220/0x440
[ 230.682161] [<ffff8000002884c4>] __writeback_inodes_wb+0xa4/0xe8
[ 230.690242] [<ffff800000288858>] wb_writeback+0x260/0x338
[ 230.697704] [<ffff800000289300>] wb_workfn+0x348/0x478
[ 230.704879] [<ffff8000000ddc9c>] process_one_work+0x164/0x458
[ 230.712661] [<ffff8000000de0bc>] worker_thread+0x12c/0x4b8
[ 230.720164] [<ffff8000000e4e90>] kthread+0xf8/0x110
[ 230.727030] [<ffff800000085c10>] ret_from_fork+0x10/0x40
[ 230.734301] Code: a94573fb a8cf7bfd d65f03c0 d503201f (d4210000)
[ 230.742400] ---[ end trace 600acdba70af5dd0 ]---