Re: [PATCH, RFC] xfs: fix multi-AG deadlock in xfs_bunmapi

Nikolay Borisov
2017-07-19T13:11:44Z

On 18.07.2017 20:25, Christoph Hellwig wrote:
> Just like in the allocator we must avoid touching multiple AGs out of
> order when freeing blocks, as freeing still locks the AGF and can cause
> the same AB-BA deadlocks as in the allocation path.
>
> Signed-off-by: Christoph Hellwig <hch@lst.d> Reported-by: Nikolay Borisov <n.borisov.lkml@gmail.com>

Unfortunately I this patch is not enough. I just tested on a 3.12 kernel ( the issue was easiest to repro there)
and I still get stack traces. I will also test on a 4.4-based kernel as well but I assume the results are going to
be the same.

Excerpt:

[ 8167.898643] SysRq : Show Blocked State
[ 8167.902006] fio D 0000000000000005 0 15744 15690 0x00000000
[ 8167.902006] ffff88007f81d390 0000000000000086 0000000000000002 ffff8800952720a0
[ 8167.902006] ffff88007f81dfd8 ffff88007f81dfd8 ffff88007f81dfd8 ffff8800952720a0
[ 8167.902006] ffff88007a462f30 7fffffffffffffff ffff8800952720a0 0000000000000001
[ 8167.902006] Call Trace:
[ 8167.902006] [<ffffffff81524ff9>] schedule_timeout+0x1d9/0x2a0
[ 8167.902006] [<ffffffff81528960>] __down+0x70/0x100
[ 8167.902006] [<ffffffff810a231c>] down+0x3c/0x50
[ 8167.902006] [<ffffffffa01e0b13>] xfs_buf_lock+0x33/0x100 [xfs]
[ 8167.902006] [<ffffffffa01e0dce>] _xfs_buf_find+0x1ee/0x420 [xfs]
[ 8167.902006] [<ffffffffa01e12d3>] xfs_buf_get_map+0x23/0x200 [xfs]
[ 8167.902006] [<ffffffffa01e2141>] xfs_buf_read_map+0x21/0x160 [xfs]
[ 8167.902006] [<ffffffffa0254423>] xfs_trans_read_buf_map+0x413/0x5d0 [xfs]
[ 8167.902006] [<ffffffffa0200561>] xfs_read_agf+0xa1/0x150 [xfs]
[ 8167.902006] [<ffffffffa020066d>] xfs_alloc_read_agf+0x5d/0x180 [xfs]
[ 8167.902006] [<ffffffffa0200c00>] xfs_alloc_fix_freelist+0x430/0x4c0 [xfs]
[ 8167.902006] [<ffffffffa0200ebb>] xfs_alloc_vextent+0x22b/0x7b0 [xfs]
[ 8167.902006] [<ffffffffa02143f7>] xfs_bmap_btalloc+0x407/0x960 [xfs]
[ 8167.902006] [<ffffffffa021506e>] __xfs_bmapi_allocate+0xde/0x340 [xfs]
[ 8167.902006] [<ffffffffa01ddc55>] xfs_bmapi_allocate+0xa5/0xb0 [xfs]
[ 8167.902006] [<ffffffffa0215914>] xfs_bmapi_write+0x644/0xab0 [xfs]
[ 8167.902006] [<ffffffffa01ef589>] xfs_iomap_write_direct+0x1e9/0x390 [xfs]
[ 8167.902006] [<ffffffffa01d9f24>] __xfs_get_blocks+0x494/0x930 [xfs]
[ 8167.902006] [<ffffffff811efbdc>] do_blockdev_direct_IO+0xadc/0x2ea0
[ 8167.902006] [<ffffffffa01d8b48>] xfs_vm_direct_IO+0x78/0xa0 [xfs]
[ 8167.902006] [<ffffffffa01e7751>] xfs_file_dio_aio_write.isra.9+0x171/0x430 [xfs]
[ 8167.902006] [<ffffffffa01e7d35>] xfs_file_aio_write+0x155/0x170 [xfs]
[ 8167.902006] [<ffffffff81201847>] do_io_submit+0x797/0x830
[ 8167.902006] [<ffffffff81533249>] system_call_fastpath+0x16/0x1b
[ 8167.902006] [<00007f73754296f7>] 0x7f73754296f6
[ 8167.902006] fio D ffff8801394b20a0 0 15746 15690 0x00000000
[ 8167.902006] ffff8800741c5390 0000000000000086 0000000000000010 ffff8801394b20a0
[ 8167.902006] ffff8800741c5fd8 ffff8800741c5fd8 ffff8800741c5fd8 ffff8801394b20a0
[ 8167.902006] ffff88007a462030 7fffffffffffffff ffff8801394b20a0 00000000015f9001
[ 8167.902006] Call Trace:
[ 8167.902006] [<ffffffff81524ff9>] schedule_timeout+0x1d9/0x2a0
[ 8167.902006] [<ffffffff81528960>] __down+0x70/0x100
[ 8167.902006] [<ffffffff810a231c>] down+0x3c/0x50
[ 8167.902006] [<ffffffffa01e0b13>] xfs_buf_lock+0x33/0x100 [xfs]
[ 8167.902006] [<ffffffffa01e0dce>] _xfs_buf_find+0x1ee/0x420 [xfs]
[ 8167.902006] [<ffffffffa01e12d3>] xfs_buf_get_map+0x23/0x200 [xfs]
[ 8167.902006] [<ffffffffa01e2141>] xfs_buf_read_map+0x21/0x160 [xfs]
[ 8167.902006] [<ffffffffa0254423>] xfs_trans_read_buf_map+0x413/0x5d0 [xfs]
[ 8167.902006] [<ffffffffa0200561>] xfs_read_agf+0xa1/0x150 [xfs]
[ 8167.902006] [<ffffffffa020066d>] xfs_alloc_read_agf+0x5d/0x180 [xfs]
[ 8167.902006] [<ffffffffa0200c00>] xfs_alloc_fix_freelist+0x430/0x4c0 [xfs]
[ 8167.902006] [<ffffffffa0200ebb>] xfs_alloc_vextent+0x22b/0x7b0 [xfs]
[ 8167.902006] [<ffffffffa02143f7>] xfs_bmap_btalloc+0x407/0x960 [xfs]
[ 8167.902006] [<ffffffffa021506e>] __xfs_bmapi_allocate+0xde/0x340 [xfs]
[ 8167.902006] [<ffffffffa01ddc55>] xfs_bmapi_allocate+0xa5/0xb0 [xfs]
[ 8167.902006] [<ffffffffa0215914>] xfs_bmapi_write+0x644/0xab0 [xfs]
[ 8167.902006] [<ffffffffa01ef589>] xfs_iomap_write_direct+0x1e9/0x390 [xfs]
[ 8167.902006] [<ffffffffa01d9f24>] __xfs_get_blocks+0x494/0x930 [xfs]
[ 8167.902006] [<ffffffff811efbdc>] do_blockdev_direct_IO+0xadc/0x2ea0
[ 8167.902006] [<ffffffffa01d8b48>] xfs_vm_direct_IO+0x78/0xa0 [xfs]
[ 8167.902006] [<ffffffffa01e7751>] xfs_file_dio_aio_write.isra.9+0x171/0x430 [xfs]
[ 8167.902006] [<ffffffffa01e7d35>] xfs_file_aio_write+0x155/0x170 [xfs]
[ 8167.902006] [<ffffffff81201847>] do_io_submit+0x797/0x830
[ 8167.902006] [<ffffffff81533249>] system_call_fastpath+0x16/0x1b
[ 8167.902006] [<00007f73754296f7>] 0x7f73754296f6
[ 8167.902006] fio D ffffffff81625900 0 15747 15690 0x00000000
[ 8167.902006] ffff88004be11390 0000000000000086 00000000000003ff ffff8800b9a94140
[ 8167.902006] ffff88004be11fd8 ffff88004be11fd8 ffff88004be11fd8 ffff8800b9a94140
[ 8167.902006] ffff88007a462f30 7fffffffffffffff ffff8800b9a94140 0000000000000001
[ 8167.902006] Call Trace:
[ 8167.902006] [<ffffffff81524ff9>] schedule_timeout+0x1d9/0x2a0
[ 8167.902006] [<ffffffff81528960>] __down+0x70/0x100
[ 8167.902006] [<ffffffff810a231c>] down+0x3c/0x50
[ 8167.902006] [<ffffffffa01e0b13>] xfs_buf_lock+0x33/0x100 [xfs]
[ 8167.902006] [<ffffffffa01e0dce>] _xfs_buf_find+0x1ee/0x420 [xfs]
[ 8167.902006] [<ffffffffa01e12d3>] xfs_buf_get_map+0x23/0x200 [xfs]
[ 8167.902006] [<ffffffffa01e2141>] xfs_buf_read_map+0x21/0x160 [xfs]
[ 8167.902006] [<ffffffffa0254423>] xfs_trans_read_buf_map+0x413/0x5d0 [xfs]
[ 8167.902006] [<ffffffffa0200561>] xfs_read_agf+0xa1/0x150 [xfs]
[ 8167.902006] [<ffffffffa020066d>] xfs_alloc_read_agf+0x5d/0x180 [xfs]
[ 8167.902006] [<ffffffffa0200c00>] xfs_alloc_fix_freelist+0x430/0x4c0 [xfs]
[ 8167.902006] [<ffffffffa0200ebb>] xfs_alloc_vextent+0x22b/0x7b0 [xfs]
[ 8167.902006] [<ffffffffa02143f7>] xfs_bmap_btalloc+0x407/0x960 [xfs]
[ 8167.902006] [<ffffffffa021506e>] __xfs_bmapi_allocate+0xde/0x340 [xfs]
[ 8167.902006] [<ffffffffa01ddc55>] xfs_bmapi_allocate+0xa5/0xb0 [xfs]
[ 8167.902006] [<ffffffffa0215914>] xfs_bmapi_write+0x644/0xab0 [xfs]
[ 8167.902006] [<ffffffffa01ef589>] xfs_iomap_write_direct+0x1e9/0x390 [xfs]
[ 8167.902006] [<ffffffffa01d9f24>] __xfs_get_blocks+0x494/0x930 [xfs]
[ 8167.902006] [<ffffffff811efbdc>] do_blockdev_direct_IO+0xadc/0x2ea0
[ 8167.902006] [<ffffffffa01d8b48>] xfs_vm_direct_IO+0x78/0xa0 [xfs]
[ 8167.902006] [<ffffffffa01e7751>] xfs_file_dio_aio_write.isra.9+0x171/0x430 [xfs]
[ 8167.902006] [<ffffffffa01e7d35>] xfs_file_aio_write+0x155/0x170 [xfs]
[ 8167.902006] [<ffffffff81201847>] do_io_submit+0x797/0x830
[ 8167.902006] [<ffffffff81533249>] system_call_fastpath+0x16/0x1b
[ 8167.902006] [<00007f73754296f7>] 0x7f73754296f6
[ 8167.902006] fio D ffffffff81625900 0 15748 15690 0x00000000
[ 8167.902006] ffff8800b5c35390 0000000000000086 00000000000003ff ffff8800b9a90000
[ 8167.902006] ffff8800b5c35fd8 ffff8800b5c35fd8 ffff8800b5c35fd8 ffff8800b9a90000
[ 8167.902006] ffff88007a462f30 7fffffffffffffff ffff8800b9a90000 0000000000000001
[ 8167.902006] Call Trace:
[ 8167.902006] [<ffffffff81524ff9>] schedule_timeout+0x1d9/0x2a0
[ 8167.902006] [<ffffffff81528960>] __down+0x70/0x100
[ 8167.902006] [<ffffffffa01e0dce>] _xfs_buf_find+0x1ee/0x420 [xfs]
[ 8167.902006] [<ffffffffa01e12d3>] xfs_buf_get_map+0x23/0x200 [xfs]
[ 8167.902006] [<ffffffffa01e2141>] xfs_buf_read_map+0x21/0x160 [xfs]
[ 8167.902006] [<ffffffffa0254423>] xfs_trans_read_buf_map+0x413/0x5d0 [xfs]
[ 8167.902006] [<ffffffffa0200561>] xfs_read_agf+0xa1/0x150 [xfs]
[ 8167.902006] [<ffffffffa020066d>] xfs_alloc_read_agf+0x5d/0x180 [xfs]
[ 8167.902006] [<ffffffffa0200c00>] xfs_alloc_fix_freelist+0x430/0x4c0 [xfs]
[ 8167.902006] [<ffffffffa0200ebb>] xfs_alloc_vextent+0x22b/0x7b0 [xfs]
[ 8167.902006] [<ffffffffa02142ed>] xfs_bmap_btalloc+0x2fd/0x960 [xfs]
[ 8167.902006] [<ffffffffa021506e>] __xfs_bmapi_allocate+0xde/0x340 [xfs]
[ 8167.902006] [<ffffffffa01ddc55>] xfs_bmapi_allocate+0xa5/0xb0 [xfs]
[ 8167.902006] [<ffffffffa0215914>] xfs_bmapi_write+0x644/0xab0 [xfs]
[ 8167.902006] [<ffffffffa01ef589>] xfs_iomap_write_direct+0x1e9/0x390 [xfs]
[ 8167.902006] [<ffffffffa01d9f24>] __xfs_get_blocks+0x494/0x930 [xfs]
[ 8167.902006] [<ffffffff811efbdc>] do_blockdev_direct_IO+0xadc/0x2ea0
[ 8167.902006] [<ffffffffa01d8b48>] xfs_vm_direct_IO+0x78/0xa0 [xfs]
[ 8167.902006] [<ffffffffa01e7751>] xfs_file_dio_aio_write.isra.9+0x171/0x430 [xfs]
[ 8167.902006] [<ffffffffa01e7d35>] xfs_file_aio_write+0x155/0x170 [xfs]
[ 8167.902006] [<ffffffff81201847>] do_io_submit+0x797/0x830
[ 8167.902006] [<ffffffff81533249>] system_call_fastpath+0x16/0x1b
[ 8167.902006] [<00007f73754296f7>] 0x7f73754296f6
[ 8167.902006] fio D ffffffff81625900 0 15749 15690 0x00000000
[ 8167.902006] ffff8800b5c0fc10 0000000000000082 0000000000000003 ffff8800b8800000
[ 8167.902006] ffff8800b5c0ffd8 ffff8800b5c0ffd8 ffff8800b5c0ffd8 ffff8800b8800000
[ 8167.902006] ffff8800b5c0fd20 ffff8800b5c0fd18 7fffffffffffffff ffff8800b8800000
[ 8167.902006] xfs_io D ffffffff81625900 0 15854 15342 0x00000000
[ 8167.902006] ffff880095179910 0000000000000082 ffff8801396f9c80 ffff88004bc40000
[ 8167.902006] ffff880095179fd8 ffff880095179fd8 ffff880095179fd8 ffff88004bc40000
[ 8167.902006] ffff88007a462030 7fffffffffffffff ffff88004bc40000 00000000015f9001
[ 8167.902006] Call Trace:
[ 8167.902006] [<ffffffff81524ff9>] schedule_timeout+0x1d9/0x2a0
[ 8167.902006] [<ffffffff81528960>] __down+0x70/0x100
[ 8167.902006] [<ffffffff810a231c>] down+0x3c/0x50
[ 8167.902006] [<ffffffffa01e0b13>] xfs_buf_lock+0x33/0x100 [xfs]
[ 8167.902006] [<ffffffffa01e0dce>] _xfs_buf_find+0x1ee/0x420 [xfs]
[ 8167.902006] [<ffffffffa01e12d3>] xfs_buf_get_map+0x23/0x200 [xfs]
[ 8167.902006] [<ffffffffa01e2141>] xfs_buf_read_map+0x21/0x160 [xfs]
[ 8167.902006] [<ffffffffa0254423>] xfs_trans_read_buf_map+0x413/0x5d0 [xfs]
[ 8167.902006] [<ffffffffa0200561>] xfs_read_agf+0xa1/0x150 [xfs]
[ 8167.902006] [<ffffffffa020066d>] xfs_alloc_read_agf+0x5d/0x180 [xfs]
[ 8167.902006] [<ffffffffa0200c00>] xfs_alloc_fix_freelist+0x430/0x4c0 [xfs]
[ 8167.902006] [<ffffffffa0201509>] xfs_free_extent+0xc9/0x140 [xfs]
[ 8167.902006] [<ffffffffa01dd69a>] xfs_bmap_finish+0x15a/0x1b0 [xfs]
[ 8167.902006] [<ffffffffa023a21e>] xfs_itruncate_extents+0x2ce/0x470 [xfs]
[ 8167.902006] [<ffffffffa01f19c3>] xfs_setattr_size+0x353/0x3f0 [xfs]
[ 8167.902006] [<ffffffffa01f1b70>] xfs_vn_setattr+0x60/0x80 [xfs]
[ 8167.902006] [<ffffffff811d0a51>] notify_change+0x241/0x3b0
[ 8167.902006] [<ffffffff811b1b92>] do_truncate+0x62/0x90
[ 8167.902006] [<ffffffff811b1f0b>] do_sys_ftruncate.constprop.11+0x12b/0x180