Date: Wed, 21 Dec 2011 22:28:42 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: John Baldwin <jhb@freebsd.org> Cc: mdf@freebsd.org, Robert Watson <rwatson@freebsd.org>, current@freebsd.org Subject: Re: extattr_set_*() return type Message-ID: <20111221202842.GZ50300@deviant.kiev.zoral.com.ua> In-Reply-To: <201112211225.18581.jhb@freebsd.org> References: <201112201649.06265.jhb@freebsd.org> <201112211031.11977.jhb@freebsd.org> <20111221161310.GW50300@deviant.kiev.zoral.com.ua> <201112211225.18581.jhb@freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
--D8moR97HX12ax1eu
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable
On Wed, Dec 21, 2011 at 12:25:18PM -0500, John Baldwin wrote:
> On Wednesday, December 21, 2011 11:13:10 am Kostik Belousov wrote:
> > On Wed, Dec 21, 2011 at 10:31:11AM -0500, John Baldwin wrote:
> > > On Tuesday, December 20, 2011 5:18:58 pm mdf@freebsd.org wrote:
> > > > On Tue, Dec 20, 2011 at 1:49 PM, John Baldwin <jhb@freebsd.org> wro=
te:
> > > > > Hmm, if these functions are expected to operate like 'write(2)' a=
nd are
> > > > > supposed to return the number of bytes written, shouldn't their r=
eturn value
> > > > > be 'ssize_t' instead of 'int'? It looks like the system calls th=
emselves
> > > > > already do the right thing in setting td_retval[] (they assign a =
ssize_t to it
> > > > > and td_retval[0] can hold a ssize_t on all of our current platfor=
ms). It
> > > > > would seem that the only change would be to the header and probab=
ly
> > > > > syscalls.master. I guess this would require a symver bump to fix=
though.
> > > >=20
> > > > An extended attribute larger than 2GB is a programming abuse, thoug=
h.
> > > > Technically int may not be 32 bits but it is on all supported
> > > > platforms now.
> > >=20
> > > Today it is an abuse. In the 90's a 64-bit off_t was considered an a=
buse by
> > > some. :)
> > >=20
> > > The type should match the documented behavior. On OS X the set opera=
tion
> > > doesn't return a size but instead returns a simple success/failure (0=
or -1)
> > > for which an int is appropriate. However, the FreeBSD API documents =
that it
> > > operates like write and consumes the buffer. Note that the size of =
the
> > > buffer passed to the 'set' and 'get' operations is a size_t, not an i=
nt, and
> > > the 'get' operations already return a ssize_t, not an int.
> >=20
> > Note that read(2)/write(2) do return int. I still have WIP patch to fix
> > this, but after some conversations with Bruce I am not sure it is worth
> > finishing.
>=20
> The manpages and /usr/include/unistd.h claim they return ssize_t. Is this
> related to the changes to make uio_resid a size_t (I thought that went in=
to
> the tree)? If the problem is that the values read/write return may fall =
into
> the range of only an int even on 64-bit platforms, that is different from=
the
> return type which is part of the ABI.
Yes, it is related. The type change for uio was done in advance.
Take a look at the first statement of sys_read() and sys_write():
if (uap->nbyte > INT_MAX)
return (EINVAL);
and at the copyinio(), which is used by scatter/gather versions of i/o
syscalls to copy in uiovec:
if (iov->iov_len > INT_MAX - uio->uio_resid) {
free(uio, M_IOV);
return (EINVAL);
--D8moR97HX12ax1eu
Content-Type: application/pgp-signature
Content-Disposition: inline
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.18 (FreeBSD)
iEYEARECAAYFAk7yQXoACgkQC3+MBN1Mb4jaOwCgkR+atYErjar9X+ZbW0IOkyPI
tskAoKbp7C/X/oYD5lMUQgB81/vupuME
=7385
-----END PGP SIGNATURE-----
--D8moR97HX12ax1eu--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20111221202842.GZ50300>