linux-kernel - Re: 6.12 WARNING in netfs_consume_read

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Message-ID: <CAKPOu+8a6EW_Ao65+aK-0ougWEzy_0yuwf3Dit89LuU8vEsJ2Q@mail.gmail.com>
Date: Sat, 7 Dec 2024 19:39:15 +0100
From: Max Kellermann <max.kellermann@...os.com>
To: David Howells <dhowells@...hat.com>
Cc: Jeff Layton <jlayton@...nel.org>, netfs@...ts.linux.dev, 
	linux-fsdevel <linux-fsdevel@...r.kernel.org>, linux-kernel@...r.kernel.org
Subject: Re: 6.12 WARNING in netfs_consume_read_data()

On Fri, Dec 6, 2024 at 10:13 PM David Howells <dhowells@...hat.com> wrote:
> Can you get some tracing for me?

Here's a Brotli-compressed trace (of 6.12.3 +
dhowells/netfs-writeback). I can reproduce it this way:

1. log in via SSH (cm4all-lukko is our SSH server)
2. "cp" a file on the Ceph home directory
3. log out - bash hangs inside write():

[<0>] folio_wait_bit_common+0x23a/0x4f0
[<0>] folio_wait_private_2_killable+0x3b/0x80
[<0>] netfs_write_begin+0x5a5/0xb90
[<0>] ceph_write_begin+0x6f/0x150
[<0>] generic_perform_write+0x253/0x7d0
[<0>] ceph_write_iter+0xafd/0x1010
[<0>] vfs_write+0x5bc/0x1030
[<0>] ksys_write+0xee/0x1c0
[<0>] do_syscall_64+0x64/0x100
[<0>] entry_SYSCALL_64_after_hwframe+0x76/0x7e

bash tries to write the history file when logging out and that hangs.
This apparently always happens after somebody does copy_file_range on
Ceph - "cp" in my example.

Triggering this is trivial for me, so if you need any more data, I can get it.

Max

Download attachment "trace.br" of type "application/octet-stream" (178978 bytes)