minor data-typing error in 8.1 fs/devfs/devfs_vnops.c

Kostik Belousov kostikbel at gmail.com
Mon Feb 7 10:22:52 UTC 2011

On Mon, Feb 07, 2011 at 12:53:14AM -0800, perryh at pluto.rain.com wrote:
> Noticed while digging through devfs_read_f() and devfs_write_f() in
> the course of investigating some unexpected (by me) geom behavior:
>     ...
>     int ioflag, error, resid;
>     ...
>     resid = uio->uio_resid;
>     ...
>     if (uio->uio_resid != resid || ...
> IOW resid (an int) is being assigned from and compared with
> uio->uio_resid (an ssize_t).
> I suppose it's probably harmless on any arch where an (int) is at
> least as large as an (ssize_t), but strictly speaking it does look
> like a bug -- or am I missing something?

The only consequence of resid truncating uio_resid would be failure
to update access time for the devfs node, which is probably not a big

In fact, HEAD cannot generate request for i/o greater than 4GB anyway.
The type of uio_resid was increased from int to ssize_t to not break
the KBI and ease indended fix to support full size_t arguments for
read(2)/write(2). The change requires lots of careful review, and thus

I integrated your fix into the patch, see

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