[PATCHv2 0/1] xfs: soft lockups while unmapping large no. of extents

["Ritesh Harjani (IBM)" <ritesh.list@gmail.com>]

Hello,

In one of the testcases, parallel async dio writes to a file generates
large no. of extents (upto 2M or more), and then this file is cleaned up for
running other I/O tests. In the process of deleting this file, soft lockup
messages are observed. We believe this is happening due to kernel being busy
in unmapping/freeing those extents as part of the transaction processing.

This is similar observation with the same call stack which was also reported
here [1]. I also tried the qemu-img bench testcase shared in [1], and I was
able to reproduce the soft lockup with that on Power.

So as I understood from that discussion [1], that kernel is moving towards a new
preemption model, but IIUC, it is still an ongoing work.
Also IMHO, this is still a problem in upstream and in older stable kernels
which we still do support and such a fix might still be necessary for them.

RFC -> v2:
==========
1. Move cond_resched within xfs_bunmapi_range() loop

[RFC]: https://lore.kernel.org/linux-xfs/cover.1713674898.git.ritesh.list@gmail.com/
[1]: https://lore.kernel.org/all/20240110071347.3711925-1-wenjian1@xiaomi.com/

Ritesh Harjani (IBM) (1):
  xfs: Add cond_resched in xfs_bunmapi_range loop

 fs/xfs/libxfs/xfs_bmap.c | 1 +
 1 file changed, 1 insertion(+)

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2.44.0