On Wed, Jan 13, 2016 at 11:22 PM, Miu Vlad-Cosmin [off-list ref] wrote:

Hello,

In a rather basic bcache setup (one cache + mdraid backing),
I encounter a kernel problem related to bcache with 4.4.0.

In order to trigger this bug, fill the cache with some dirty data.
When there is some dirty data, wait for the bcache_writeback to
start writing it to the backing device (0-3 minutes)
and the BUG triggers.

Please find more info here: https://bugzilla.kernel.org/show_bug.cgi?id=110771

[<ffffffff815822af>] make_request+0x47f/0xca0
[<ffffffff815a5d3d>] md_make_request+0xdd/0x220
[<ffffffff810c53ce>] ? pick_next_task_fair+0x12e/0x450
[<ffffffff81311d2e>] generic_make_request+0xce/0x1b0
[<ffffffff815a1b70>] write_dirty+0x60/0xb0
[<ffffffff810aafa7>] process_one_work+0x147/0x3d0
[<ffffffff810ab546>] worker_thread+0x46/0x440
[<ffffffff810ab500>] ? rescuer_thread+0x2d0/0x2d0
[<ffffffff810ab500>] ? rescuer_thread+0x2d0/0x2d0
[<ffffffff810afeb4>] kthread+0xc4/0xe0
[<ffffffff810afdf0>] ? kthread_park+0x50/0x50
[<ffffffff8170c85f>] ret_from_fork+0x3f/0x70

A bisect shows "[578270bfbd2803dc7b0b03fbc2ac119efbc73195]
block: fix segment split" as the problem.

CC Ming Lei.

Anyone can confirm this ?

Thanks,
Vlad