On Mon, Oct 22, 2018 at 09:59:52PM +0000, Rick Macklem wrote: > > ________________________________________ > From: owner-freebsd-curr...@freebsd.org <owner-freebsd-curr...@freebsd.org> > on behalf of Rick Macklem <rmack...@uoguelph.ca> > Sent: Monday, October 22, 2018 5:24 PM > To: Brooks Davis > Cc: FreeBSD Current; Josh Paetzel > Subject: Re: which way to update export_args structure? > > Brooks Davis wrote: > On Sat, Oct 20, 2018 at 01:17:37AM +0000, Rick Macklem wrote: > [lots of stuff snipped] > >> + if (vfs_getopt(mp->mnt_optnew, "export", &bufp, &len) == 0) { > >> + /* Assume that there is only 1 ABI for each length. > >> */ > >> + switch (len) { > >> + case (sizeof(struct oexport_args)): > >> + case (sizeof(struct o2export_args)): > ... > >> + memset(&o2export, 0, sizeof(o2export)); > > > >This is certainly redundant given that you immediately copy over it. > Actually, I just looked and this code is correct. The trick is that "len" > might > equal sizeof(struct oexport_args) which is < sizeof(struct o2export_args). > As such, the memcpy() may only replace the first fields of "struct > o2export_args". > I've added a comment to the patch to clarify this.
Ah, that makes sense. -- Brooks
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