On Wed, Apr 17, 2024 at 09:51:48AM -0400, Benjamin Coddington wrote:
> On 17 Apr 2024, at 8:40, Dan Carpenter wrote:
>
> > On Wed, Apr 17, 2024 at 08:00:04AM -0400, Benjamin Coddington wrote:
> >> On 15 Apr 2024, at 4:08, Dan Carpenter wrote:
> >>
> >>> [ Why is Smatch only complaining now, 2 years later??? It is a mystery.
> >>> -dan ]
> >>>
> >>> Hello Benjamin Coddington,
> >>
> >> Hi Dan!
> >>
> >>> Commit c3ed222745d9 ("NFSv4: Fix free of uninitialized nfs4_label on
> >>> referral lookup.") from May 14, 2022 (linux-next), leads to the
> >>> following Smatch static checker warning:
> >>>
> >>> fs/nfs/nfs4state.c:2138 nfs4_try_migration()
> >>> warn: missing error code here? 'nfs_alloc_fattr()' failed. 'result' = '0'
> >>>
> >>> fs/nfs/nfs4state.c
> >>> 2115 static int nfs4_try_migration(struct nfs_server *server, const struct cred *cred)
> >>> 2116 {
> >>> 2117 struct nfs_client *clp = server->nfs_client;
> >>> 2118 struct nfs4_fs_locations *locations = NULL;
> >>> 2119 struct inode *inode;
> >>> 2120 struct page *page;
> >>> 2121 int status, result;
> >>> 2122
> >>> 2123 dprintk("--> %s: FSID %llx:%llx on \"%s\"\n", __func__,
> >>> 2124 (unsigned long long)server->fsid.major,
> >>> 2125 (unsigned long long)server->fsid.minor,
> >>> 2126 clp->cl_hostname);
> >>> 2127
> >>> 2128 result = 0;
> >>> ^^^^^^^^^^^
> >>>
> >>> 2129 page = alloc_page(GFP_KERNEL);
> >>> 2130 locations = kmalloc(sizeof(struct nfs4_fs_locations), GFP_KERNEL);
> >>> 2131 if (page == NULL || locations == NULL) {
> >>> 2132 dprintk("<-- %s: no memory\n", __func__);
> >>> 2133 goto out;
> >>> ^^^^^^^^
> >>> Success.
> >>>
> >>> 2134 }
> >>> 2135 locations->fattr = nfs_alloc_fattr();
> >>> 2136 if (locations->fattr == NULL) {
> >>> 2137 dprintk("<-- %s: no memory\n", __func__);
> >>> --> 2138 goto out;
> >>> ^^^^^^^^^
> >>> Here too.
> >>
> >> My patch was following the precedent set by c9fdeb280b8cc. I believe the
> >> idea is that the function can fail without an error and the client will
> >> retry the next time the server says -NFS4ERR_MOVED.
> >>
> >> Is there a way to appease smatch here? I don't have a lot of smatch
> >> smarts.
> >
> > Generally, I tell people to just ignore it. Anyone with questions can
> > look up this email thread.
> >
> > But if you really wanted to silence it, Smatch counts it as intentional
> > if the "result = 0;" is within five lines of the goto out.
>
> Good to know! In this case, I think the maintainers would show annoyance
> with that sort of patch. A comment here about the successful return code on
> an allocation failure would have avoided this, and I probably should have
> recognized this patch might create an issue and inserted one. Thanks for
> the report.
To me ignoring it is fine or adding a comment is even better, but I also
think adding a bunch of "ret = 0;" assignments should not be as
controversial as people make it out to be.
It's just a style debate, right? The compiler knows that ret is already
zero and it's going to optimize them away. So it doesn't affect the
compiled code.
You could add a comment /* ret is zero intentionally */ or you could
just add a "ret = 0;". Neither affects the compile code. But to me, I
would prefer the code, because when I see the comment, then I
immediately start scrolling back to see if ret is really zero. I like
when the code looks deliberate. When you see a "ret = 0;" there isn't
any question about the author's intent.
But again, I don't feel strongly about this.
regards,
dan carpenter
