From: Matthew Wilcox <willy@infradead.org>
To: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-ext4@vger.kernel.org, gfs2@lists.linux.dev,
linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org,
"Darrick J . Wong" <djwong@kernel.org>,
linux-erofs@lists.ozlabs.org, Theodore Ts'o <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>
Subject: Re: [PATCH 2/3] mm: Add folio_fill_tail() and use it in iomap
Date: Fri, 10 Nov 2023 17:09:27 +0000 [thread overview]
Message-ID: <ZU5jx2QeujE+868t@casper.infradead.org> (raw)
In-Reply-To: <CAHc6FU550j_AYgWz5JgRu84mw5HqrSwd+hYZiHVArnget3gb4w@mail.gmail.com>
On Thu, Nov 09, 2023 at 10:50:45PM +0100, Andreas Gruenbacher wrote:
> On Tue, Nov 7, 2023 at 10:27 PM Matthew Wilcox (Oracle)
> <willy@infradead.org> wrote:
> > +static inline void folio_fill_tail(struct folio *folio, size_t offset,
> > + const char *from, size_t len)
> > +{
> > + char *to = kmap_local_folio(folio, offset);
> > +
> > + VM_BUG_ON(offset + len > folio_size(folio));
> > +
> > + if (folio_test_highmem(folio)) {
> > + size_t max = PAGE_SIZE - offset_in_page(offset);
> > +
> > + while (len > max) {
> > + memcpy(to, from, max);
> > + kunmap_local(to);
> > + len -= max;
> > + from += max;
> > + offset += max;
> > + max = PAGE_SIZE;
> > + to = kmap_local_folio(folio, offset);
> > + }
> > + }
> > +
> > + memcpy(to, from, len);
> > + to = folio_zero_tail(folio, offset, to);
>
> This needs to be:
>
> to = folio_zero_tail(folio, offset + len, to + len);
Oh, wow, that was stupid of me. I only ran an xfstests against ext4,
which doesn't exercise this code, not gfs2 or erofs. Thanks for
fixing this up.
I was wondering about adding the assertion:
VM_BUG_ON((kaddr - offset) % PAGE_SIZE);
to catch the possible mistake of calling kmap_local_folio(folio, 0)
instead of kmap_local_folio(folio, offset). But maybe that's
sufficiently unlikely a mistake to bother adding a runtime check for.
next prev parent reply other threads:[~2023-11-10 17:09 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-07 21:26 [PATCH 0/3] Add folio_zero_tail() and folio_fill_tail() Matthew Wilcox (Oracle)
2023-11-07 21:26 ` [PATCH 1/3] mm: Add folio_zero_tail() and use it in ext4 Matthew Wilcox (Oracle)
2023-11-08 23:06 ` Andrew Morton
2023-11-09 0:12 ` Andreas Grünbacher
2023-11-09 17:27 ` Andrew Morton
2023-11-09 17:37 ` Matthew Wilcox
2023-11-09 21:50 ` Andreas Gruenbacher
2023-11-07 21:26 ` [PATCH 2/3] mm: Add folio_fill_tail() and use it in iomap Matthew Wilcox (Oracle)
2023-11-09 21:50 ` Andreas Gruenbacher
2023-11-10 17:09 ` Matthew Wilcox [this message]
2023-11-10 17:50 ` Andreas Grünbacher
2023-11-11 4:02 ` Gao Xiang
2023-11-07 21:26 ` [PATCH 3/3] gfs2: Convert stuffed_readpage() to stuffed_read_folio() Matthew Wilcox (Oracle)
2023-11-09 21:52 ` Andreas Gruenbacher
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