XFS long delays on disk full

[Andi Kleen <andi@firstfloor.org>]

Hi,

I was doing some testing on a 4.18-rc1 kernel, and a single threaded
test wrote a fairly large file to a XFS file system, causing it to
fill up.

After that the process hung in D state for a long time, and only
recovered after several minutes. Here's the backtrace during
the hang:

[<0>] wb_wait_for_completion+0x5e/0x90
[<0>] sync_inodes_sb+0xc9/0x290
[<0>] xfs_flush_inodes+0x25/0x30 [xfs]
[<0>] xfs_file_buffered_aio_write+0x2be/0x300 [xfs]
[<0>] __vfs_write+0x114/0x1a0
[<0>] vfs_write+0xad/0x1a0
[<0>] ksys_write+0x52/0xc0
[<0>] do_syscall_64+0x5b/0x160
[<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[<0>] 0xffffffffffffffff

There were no IO errors or similar.

Expected? Already fixed?

Thanks,
-Andi