linux-kernel - Re: [PATCH v7 0/6] Per-VMA lock support for swap and userfaults

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Message-ID: <ZNVeF29xUXhDwB3U@casper.infradead.org>
Date:   Thu, 10 Aug 2023 23:00:55 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     Suren Baghdasaryan <surenb@...gle.com>, akpm@...ux-foundation.org,
        hannes@...xchg.org, mhocko@...e.com, josef@...icpanda.com,
        jack@...e.cz, ldufour@...ux.ibm.com, laurent.dufour@...ibm.com,
        michel@...pinasse.org, liam.howlett@...cle.com, jglisse@...gle.com,
        vbabka@...e.cz, minchan@...gle.com, dave@...olabs.net,
        punit.agrawal@...edance.com, lstoakes@...il.com, hdanton@...a.com,
        apopple@...dia.com, peterx@...hat.com, ying.huang@...el.com,
        yuzhao@...gle.com, dhowells@...hat.com, hughd@...gle.com,
        viro@...iv.linux.org.uk, brauner@...nel.org,
        pasha.tatashin@...een.com, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com
Subject: Re: [PATCH v7 0/6] Per-VMA lock support for swap and userfaults

On Thu, Aug 10, 2023 at 09:40:57AM +0200, David Hildenbrand wrote:
> I won't lie: all of these locking checks are a bit hard to get and possibly
> even harder to maintain.
> 
> Maybe better mmap unlock sanity checks as spelled out above might help
> improve part of the situation.
> 
> 
> And maybe some comments regarding the placement might help as well ;)

The placement was obvious; we can't call into drivers under the vma
lock.  Not until we've audited all of them.  I haven't yet had the
chance to figure out exactly what is being fixed with this patch ...
give me a few minutes.