linux-kernel - Re: [RFC v2 1/8] page_flags: add is_folio

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Message-ID: <ZHC5Zm3t9JIITu3h@casper.infradead.org>
Date:   Fri, 26 May 2023 14:51:34 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     hughd@...gle.com, akpm@...ux-foundation.org, brauner@...nel.org,
        djwong@...nel.org, p.raghav@...sung.com, da.gomez@...sung.com,
        rohan.puri@...sung.com, rpuri.linux@...il.com,
        a.manzanares@...sung.com, dave@...olabs.net, yosryahmed@...gle.com,
        keescook@...omium.org, hare@...e.de, kbusch@...nel.org,
        patches@...ts.linux.dev, linux-block@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC v2 1/8] page_flags: add is_folio_hwpoison()

On Fri, May 26, 2023 at 12:55:45AM -0700, Luis Chamberlain wrote:
> Provide a helper similar to is_page_hwpoison() for folios
> which tests the first head and if the folio is large any page in
> the folio is tested for the poison flag.

But it's not "is poison".  it's "contains poison".  So how about
folio_contains_hwpoison() as a name?

But what do you really want to know here?  In the Glorious Future,
individual pages get their memdesc pointer set to be a hwpoison
pointer.  Are we going to need to retain a bit in every memdesc to
say whether one of the pages in the memdesc has been poisoned?

Or can we get away with just testing individual pages as we look at
them?