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When CONFIG_DEBUG_NET_SMALL_RTNL is off, rtnl_net_dereference() is the
static inline wrapper of rtnl_dereference() returning a plain (void *)
pointer to make sure net is always evaluated as requested in [0].
But, it makes sparse complain [1] when the pointer has __rcu annotation:
net/ipv4/devinet.c:674:47: sparse: warning: incorrect type in argument 2 (different address spaces)
net/ipv4/devinet.c:674:47: sparse: expected void *p
net/ipv4/devinet.c:674:47: sparse: got struct in_ifaddr [noderef] __rcu *
Also, if we evaluate net as (void *) in a macro, then the compiler
in turn fails to build due to -Werror=unused-value.
#define rtnl_net_dereference(net, p) \
({ \
(void *)net; \
rtnl_dereference(p); \
})
net/ipv4/devinet.c: In function ‘inet_rtm_deladdr’:
./include/linux/rtnetlink.h:154:17: error: statement with no effect [-Werror=unused-value]
154 | (void *)net; \
net/ipv4/devinet.c:674:21: note: in expansion of macro ‘rtnl_net_dereference’
674 | (ifa = rtnl_net_dereference(net, *ifap)) != NULL;
| ^~~~~~~~~~~~~~~~~~~~
Let's go back to the original simplest macro.
Note that checkpatch complains about this approach, but it's one-shot and
less noisy than the other two.
WARNING: Argument 'net' is not used in function-like macro
#76: FILE: include/linux/rtnetlink.h:142:
+#define rtnl_net_dereference(net, p) \
+ rtnl_dereference(p)
Fixes: 844e5e7e65 ("rtnetlink: Add assertion helpers for per-netns RTNL.")
Link: https://lore.kernel.org/netdev/20241004132145.7fd208e9@kernel.org/ [0]
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202410200325.SaEJmyZS-lkp@intel.com/ [1]
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.