Re: [git pull] vfs pile 1 (splice)

From: Linus Torvalds
Date: Sun Oct 09 2016 - 15:12:17 EST

On Sun, Oct 9, 2016 at 11:40 AM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> I'll continue with *just* SLUB debugging on, but I thought it was
> interesting how enabling more memory access debugging actually ends up
> changing some really subtle code.

Indeed, now with DEBUG_PAGEALLOC disabled, I got a crash again. It
apparently happened earlier in the call chain (so maybe the slub
debugging found something), which should be good. Except it now
happens in a context where I just see a hung machine, and nothing
makes it onto the screen or into the logs ;(

So this thing is apparently not all that hard to trigger, but it
doesn't exactly seem easy either. It tends to happen fairly soon after
a reboot, which makes me suspect it's some cold-cache issue, but that
doesn't narrow things down as much as you'd think. It could still be
the block layer changes, but it could also equally well be the ext4

I don't think there's any splice activity anywhere, but who knows. And
the splice changes could have buggered the pipe locking, so..

Anyway, I don't think I can bisect it, but I'll try to narrow it down
a *bit* at least.

Not doing any more pulls on this unstable base, I've been puttering
around in trying to clean up some stupid printk logging issues