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Date:   Wed, 6 Oct 2021 16:38:49 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Al Viro <viro@zeniv.linux.org.uk>
Cc:     linux-mm@kvack.org, David Hildenbrand <david@redhat.com>,
        Kent Overstreet <kent.overstreet@gmail.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        linux-fsdevel@vger.kernel.org
Subject: Re: [RFC] pgflags_t
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On Wed, Oct 06, 2021 at 03:22:29PM +0000, Al Viro wrote:
> On Wed, Oct 06, 2021 at 03:58:14PM +0100, Matthew Wilcox wrote:
> > David expressed some unease about the lack of typesafety in patches
> > 1 & 2 of the page->slab conversion [1], and I'll admit to not being
> > particularly a fan of passing around an unsigned long.  That crystallised
> > in a discussion with Kent [2] about how to lock a page when you don't know
> > its type (solution: every memory descriptor type starts with a
> > pgflags_t)
> 
> Why bother making it a struct?  What's wrong with __bitwise and letting
> sparse catch conversions?

People don't run sparse.  I happen to have a built allmodconfig tree
here and running make C=2 fs/ gives 1147 lines of warnings.  Why would
adding more warnings help?