linux-kernel - Re: [PATCH] mm: Track mmu notifiers in fs_reclaim

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Date:   Tue, 23 Jun 2020 18:29:58 -0400
From:   Qian Cai <cai@....pw>
To:     Daniel Vetter <daniel@...ll.ch>
Cc:     Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        Thomas Hellström <thomas_os@...pmail.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Linux MM <linux-mm@...ck.org>,
        linux-rdma <linux-rdma@...r.kernel.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Christian König <christian.koenig@....com>,
        Daniel Vetter <daniel.vetter@...el.com>,
        linux-xfs@...r.kernel.org
Subject: Re: [PATCH] mm: Track mmu notifiers in fs_reclaim_acquire/release



> On Jun 23, 2020, at 6:13 PM, Daniel Vetter <daniel@...ll.ch> wrote:
> 
> Ok I tested this. I can't use your script to repro because
> - I don't have a setup with xfs, and the splat points at an issue in xfs
> - reproducing lockdep splats in shrinker callbacks is always a bit tricky

What’s xfs setup are you talking about? This is simple xfs rootfs and then trigger swapping. Nothing tricky here as it hit on multiple machines within a few seconds on linux-next.

> Summary: Everything is working as expected, there's no change in the
> lockdep annotations.
> I really think the problem is that either your testcase doesn't hit
> the issue reliably enough, or that you're not actually testing the
> same kernels and there's some other changes (xfs most likely, but
> really it could be anywhere) which is causing this regression. I'm
> rather convinced now after this test that it's not my stuff.

Well, the memory pressure workloads have been running for years on daily linux-next builds and never saw this one happened once. Also, the reverting is ONLY to revert your patch on the top of linux-next will stop the splat, so there is no not testing the same kernel at all.