Re: xfs/311 test pass but leave block device unusable

["Darrick J. Wong" <djwong@kernel.org>]

[cc xfs list]

On Thu, Jan 20, 2022 at 12:04:47PM +0100, Andrea Tomassetti wrote:
> Hi all,
> I was using the (x)fstest utility on the Kernel 5.11 to try to
> reproduce some xfs-related issues:
>   INFO: task xfs-conv/dm-3:1360 blocked for more than 120 seconds.
>   Workqueue: xfs-conv/dm-3 xfs_end_io [xfs]
>    Call Trace:
>     __schedule+0x44c/0x8a0
>     schedule+0x4f/0xc0
>     xlog_grant_head_wait+0xb5/0x1a0 [xfs]
>     xlog_grant_head_check+0xe1/0x100 [xfs]

Threads are stuck waiting for log space; can you post the full dmesg?
And the xfs_info output of the test device?

> When I realized that xfs test n. 311 was passing correctly but every
> further attempt to use the block device (e.g. mount it) was failing.
> The issue is reproducible after reboot.
> 
> Test passed:
>   ./check xfs/311
>   FSTYP         -- xfs (non-debug)
>   PLATFORM      -- Linux/x86_64 test 5.11.0-1021-aws
> #22~20.04.2-Ubuntu SMP Wed Oct 27 21:27:13 UTC 2021
>   MKFS_OPTIONS  -- -f /dev/xvdz
>   MOUNT_OPTIONS -- /dev/xvdz /home/test/z
> 
>   xfs/311 25s ...  25s
>   Ran: xfs/311
>   Passed all 1 tests
> 
> Fail:
>   # mount /dev/xvdz /home/test/z/
>     mount: /home/test/z: /dev/xvdz already mounted or mount point busy.
>     [ 2222.028417] /dev/xvdz: Can't open blockdev
> 
> lsof does not show anything that is using either /dev/xvdz or /home/test/z
> 
> Any idea why is this happening?

xfs-conv handles unwritten extent conversion after writeback, so I would
speculate (without dmesg data) that everyone got wedged trying to start
a transaction, and the log is blocked up for whatever reason.

> The `xlog_grant_head_wait` race issue has been resolved in a later
> Kernel version, am I right?

Beats me.

> Best regards,
> Andrea
> 
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