Re: [PATCH] iomap: iomap_write_end cleanup

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On Wed, May 04, 2022 at 12:15:45AM +0200, Andreas Gruenbacher wrote:
> On Tue, May 3, 2022 at 11:53 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
> > On Tue, May 03, 2022 at 11:37:27PM +0200, Andreas Gruenbacher wrote:
> > > In iomap_write_end(), only call iomap_write_failed() on the byte range
> > > that has failed.  This should improve code readability, but doesn't fix
> > > an actual bug because iomap_write_failed() is called after updating the
> > > file size here and it only affects the memory beyond the end of the
> > > file.
> >
> > I can't find a way to set 'ret' to anything other than 0 or len.  I know
> > the code is written to make it look like we can return a short write,
> > but I can't see a way to do it.
> 
> Good point, but that doesn't make the code any less confusing in my eyes.

Not to mention it leaves a logic bomb if we ever /do/ start returning
0 < ret < len.

Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>

--D


> Thanks,
> Andreas
> 
> > > Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
> > > ---
> > >  fs/iomap/buffered-io.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> > > index 358ee1fb6f0d..8fb9b2797fc5 100644
> > > --- a/fs/iomap/buffered-io.c
> > > +++ b/fs/iomap/buffered-io.c
> > > @@ -734,7 +734,7 @@ static size_t iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
> > >       folio_put(folio);
> > >
> > >       if (ret < len)
> > > -             iomap_write_failed(iter->inode, pos, len);
> > > +             iomap_write_failed(iter->inode, pos + ret, len - ret);
> > >       return ret;
> > >  }
> > >
> > > --
> > > 2.35.1
> > >
> >
> 



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