Re: [PATCH net-next] net: skb: prevent the split of kfree_skb_reason() by gcc

[kernel test robot <lkp@intel.com>]

Hi,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on net-next/master]

url:    https://github.com/intel-lab-lkp/linux/commits/menglong8-dong-gmail-com/net-skb-prevent-the-split-of-kfree_skb_reason-by-gcc/20220811-200919
base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git f86d1fbbe7858884d6754534a0afbb74fc30bc26
config: riscv-randconfig-r042-20220811 (https://download.01.org/0day-ci/archive/20220812/202208120238.cz3RvV74-lkp@intel.com/config)
compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 5f1c7e2cc5a3c07cbc2412e851a7283c1841f520)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install riscv cross compiling tool for clang build
        # apt-get install binutils-riscv64-linux-gnu
        # https://github.com/intel-lab-lkp/linux/commit/8e014b654d9e51abed132155237d855b25da06a0
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review menglong8-dong-gmail-com/net-skb-prevent-the-split-of-kfree_skb_reason-by-gcc/20220811-200919
        git checkout 8e014b654d9e51abed132155237d855b25da06a0
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash net/core/

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> net/core/skbuff.c:780:6: warning: unknown attribute 'optimize' ignored [-Wunknown-attributes]
   void __nofnsplit
        ^~~~~~~~~~~
   include/linux/compiler_attributes.h:374:56: note: expanded from macro '__nofnsplit'
   #define __nofnsplit                     __attribute__((optimize("O1")))
                                                          ^~~~~~~~~~~~~~
   1 warning generated.


vim +/optimize +780 net/core/skbuff.c

   770	
   771	/**
   772	 *	kfree_skb_reason - free an sk_buff with special reason
   773	 *	@skb: buffer to free
   774	 *	@reason: reason why this skb is dropped
   775	 *
   776	 *	Drop a reference to the buffer and free it if the usage count has
   777	 *	hit zero. Meanwhile, pass the drop reason to 'kfree_skb'
   778	 *	tracepoint.
   779	 */
 > 780	void __nofnsplit
   781	kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason)
   782	{
   783		if (!skb_unref(skb))
   784			return;
   785	
   786		DEBUG_NET_WARN_ON_ONCE(reason <= 0 || reason >= SKB_DROP_REASON_MAX);
   787	
   788		trace_kfree_skb(skb, __builtin_return_address(0), reason);
   789		__kfree_skb(skb);
   790	}
   791	EXPORT_SYMBOL(kfree_skb_reason);
   792	

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