linux-kernel - Re: [PATCH] maple_tree: Fix sparse reported issues

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Message-ID: <b8f67958-11cf-2fb2-aba9-6cc88c75874@google.com>
Date:   Sun, 17 Jul 2022 23:47:08 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Liam Howlett <liam.howlett@...cle.com>
cc:     Hugh Dickins <hughd@...gle.com>,
        David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Yu Zhao <yuzhao@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] maple_tree: Fix sparse reported issues

On Sun, 17 Jul 2022, Hugh Dickins wrote:
> On Mon, 18 Jul 2022, Liam Howlett wrote:
> > Do you have the patch
> > "maple_tree-Fix-stale-data-copy-in-mas_wr_node_store.patch"? It sounds
> > like your issue fits this fix exactly. I was seeing the same issue with
> > gcc 9.3.1 20200408 and this bug doesn't happen for me now.  The logs
> > you sent also fit the situation. I went through the same exercise
> > (exorcism?) of debugging the various additions and removals of the VMA
> > only to find the issue in the tree itself.  The fix also modified the
> > test code to detect the issue - which was actually hit but not detected
> > in the existing test cases from a live capture of VMA activities.  It is
> > difficult to spot in the tree dump as well.  I am sure I sent this to
> > Andrew as it is included in v11 and did not show up in his diff, but I
> > cannot find it on lore, perhaps I forgot to CC you?  I've attached it
> > here for you in case you missed it.
> 
> Thanks!  No, I never received that patch, nor can I see it on lore
> or marc.info; but I (still) haven't looked at v11, and don't know
> about Andrew's diff.  Anyway, sounds exciting, I'm eager to stop
> writing this mail and get to testing with that in - but please
> let me know whether it's the mas_dead_leaves() or the __vma_adjust()
> mods you attached previously, which you want me to leave out.

I just went ahead with both of those still in, my do_mas_munmap()
non-fix reverted, and your "Fix stale data copy" added: looks very
promising so far, been running two hours without a problem.  I
do expect it to hit the migration entry !PageLocked BUG soon (as
it quickly did on the laptop), but that's okay: I'll switch over
to thinking about that BUG, so long as tonight's run does not
crash in some other way.

Hugh