linux-kernel - PROBLEM: kernel crashes when running xfsdump since ~6.4

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Date: Thu, 20 Jun 2024 02:19:57 -0400
From: Nick Bowler <nbowler@...conx.ca>
To: linux-kernel@...r.kernel.org,
 Linux regressions mailing list <regressions@...ts.linux.dev>,
 linux-mm@...ck.org, sparclinux@...r.kernel.org,
 "Uladzislau Rezki (Sony)" <urezki@...il.com>,
 Andrew Morton <akpm@...ux-foundation.org>
Subject: PROBLEM: kernel crashes when running xfsdump since ~6.4

Hi,

After upgrading my sparc to 6.9.5 I noticed that attempting to run
xfsdump instantly (within a couple seconds) and reliably crashes the
kernel.  The same problem is also observed on 6.10-rc4.

This is a regression introduced around 6.4 timeframe.  6.3 appears
to work fine and xfsdump goes about its business dumping stuff.

Bisection implicates the following:

  062eacf57ad91b5c272f89dc964fd6dd9715ea7d is the first bad commit
  commit 062eacf57ad91b5c272f89dc964fd6dd9715ea7d
  Author: Uladzislau Rezki (Sony) <urezki@...il.com>
  Date:   Thu Mar 30 21:06:38 2023 +0200
  
      mm: vmalloc: remove a global vmap_blocks xarray

This reverts pretty easily on top of v6.10-rc4, as long as I first
revert fa1c77c13ca5 ("mm: vmalloc: rename addr_to_vb_xarray() function")
as this just causes conflicts.  Then there is one easily-corrected build
failure (adjust the one remaining &vbq->vmap_blocks back to &vmap_blocks).

If I do all of that then the kernel is not crashing anymore.

A splat like this one is output on the console when the crash occurs (varies a bit):

  spitfire_data_access_exception: SFSR[000000000080100d] SFAR[0000000000c51ba0], going.
                \|/ ____ \|/
                "@'/ .. \`@"
                /_| \__/ |_\
                   \__U_/
  xfsdump(2028): Dax [#1]
  CPU: 0 PID: 2028 Comm: xfsdump Not tainted 6.9.5 #199
  TSTATE: 0000000811001607 TPC: 0000000000974fc4 TNPC: 0000000000974fc8 Y: 00000000    Not tainted
  TPC: <queued_spin_lock_slowpath+0x1d0/0x2cc>
  g0: 0000000000aa9110 g1: 0000000000c51ba0 g2: 444b000000000000 g3: 0000000000c560c0
  g4: fffff800a71a1f00 g5: fffff800bebb6000 g6: fffff800ac0ec000 g7: 0000000000040000
  o0: 0000000000000002 o1: 00000000000007d8 o2: fffff800a4131420 o3: ffffffff0000ffff
  o4: 00000000900a2001 o5: 0000000000c4f5a0 sp: fffff800ac0eeac1 ret_pc: 0000000000040000
  RPC: <0x40000>
  l0: fffff800a40098c0 l1: 0000000100800000 l2: 0000000000000000 l3: 0000000000000103
  l4: fffff800a40081b0 l5: 0000000000aeec00 l6: fffff800a40080a0 l7: 0000000101000000
  i0: 0000000000c4f5a0 i1: 00000000900a2001 i2: 0000000000000000 i3: fffff800bf807b80
  i4: 0000000000000000 i5: fffff800bf807b80 i6: fffff800ac0eeb71 i7: 0000000000503438
  I7: <vm_map_ram+0x210/0x724>
  Call Trace:
  [<0000000000503438>] vm_map_ram+0x210/0x724
  [<00000000006661f8>] _xfs_buf_map_pages+0x58/0xa0
  [<0000000000667058>] xfs_buf_get_map+0x668/0x7a4
  [<00000000006673e0>] xfs_buf_read_map+0x20/0x160
  [<0000000000667548>] xfs_buf_readahead_map+0x28/0x38
  [<000000000067a4f8>] xfs_iwalk_ichunk_ra.isra.0+0xa8/0xc4
  [<000000000067a8f0>] xfs_iwalk_ag+0x1c0/0x260
  [<000000000067ab08>] xfs_iwalk+0xdc/0x130
  [<0000000000679fc8>] xfs_bulkstat+0x10c/0x140
  [<0000000000695528>] xfs_compat_ioc_fsbulkstat+0x1a4/0x1e8
  [<000000000069572c>] xfs_file_compat_ioctl+0x8c/0x1f4
  [<0000000000534ab0>] compat_sys_ioctl+0x9c/0xfc
  [<0000000000406214>] linux_sparc_syscall32+0x34/0x60
  Disabling lock debugging due to kernel taint
  Caller[0000000000503438]: vm_map_ram+0x210/0x724
  Caller[00000000006661f8]: _xfs_buf_map_pages+0x58/0xa0
  Caller[0000000000667058]: xfs_buf_get_map+0x668/0x7a4
  Caller[00000000006673e0]: xfs_buf_read_map+0x20/0x160
  Caller[0000000000667548]: xfs_buf_readahead_map+0x28/0x38
  Caller[000000000067a4f8]: xfs_iwalk_ichunk_ra.isra.0+0xa8/0xc4
  Caller[000000000067a8f0]: xfs_iwalk_ag+0x1c0/0x260
  Caller[000000000067ab08]: xfs_iwalk+0xdc/0x130
  Caller[0000000000679fc8]: xfs_bulkstat+0x10c/0x140
  Caller[0000000000695528]: xfs_compat_ioc_fsbulkstat+0x1a4/0x1e8
  Caller[000000000069572c]: xfs_file_compat_ioctl+0x8c/0x1f4
  Caller[0000000000534ab0]: compat_sys_ioctl+0x9c/0xfc
  Caller[0000000000406214]: linux_sparc_syscall32+0x34/0x60
  Caller[00000000f789ccdc]: 0xf789ccdc
  Instruction DUMP:
   8610e0c0
   8400c002
   c458a0f8
  <f6704002>
   c206e008
   80a06000
   12400012
   01000000
   81408000

Let me know if you need any more info!

Thanks,
  Nick