linux-kernel - Re: [PATCH] netfs: Fix missing xas_retry() calls in xarray iteration

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Date:   Fri, 04 Nov 2022 15:34:25 +0000
From:   David Howells <dhowells@...hat.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     dhowells@...hat.com, George Law <glaw@...hat.com>,
        Jeff Layton <jlayton@...nel.org>, linux-cachefs@...hat.com,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] netfs: Fix missing xas_retry() calls in xarray iteration

Matthew Wilcox <willy@...radead.org> wrote:

> "unsigned int" assumes that the number of bytes isn't going to exceed 32
> bits.  I tend to err on the side of safety here and use size_t.

Not unreasonable.

> > +		pgpos = (folio_index(folio) - start_page) * PAGE_SIZE;
> > +		pgend = pgpos + folio_size(folio);
> 
> What happens if start_page is somewhere inside folio?  Seems to me
> that pgend ends up overhanging into the next folio?

Yeah, I think my maths is dodgy.  I should probably use folio_pos() and/or
offset_in_folio().

David