[josef-btrfs:blk-iolatency-v5 14/14] mm/readahead.c:503:2: note: in expansion of macro 'if'

[kbuild test robot <lkp@xxxxxxxxx>]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/josef/btrfs-next.git blk-iolatency-v5
head:   9ca920cdc56987426bfc77c18dbfff9d99f242e3
commit: 9ca920cdc56987426bfc77c18dbfff9d99f242e3 [14/14] skip readahead if the cgroup is congested
config: x86_64-randconfig-x013-201824 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-16) 7.3.0
reproduce:
        git checkout 9ca920cdc56987426bfc77c18dbfff9d99f242e3
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All warnings (new ones prefixed by >>):

   In file included from include/linux/kernel.h:10:0,
                    from mm/readahead.c:10:
   mm/readahead.c: In function 'page_cache_sync_readahead':
   mm/readahead.c:503:6: error: implicit declaration of function 'blk_cgroup_congested'; did you mean 'bdi_rw_congested'? [-Werror=implicit-function-declaration]
     if (blk_cgroup_congested())
         ^
   include/linux/compiler.h:58:30: note: in definition of macro '__trace_if'
     if (__builtin_constant_p(!!(cond)) ? !!(cond) :   \
                                 ^~~~
>> mm/readahead.c:503:2: note: in expansion of macro 'if'
     if (blk_cgroup_congested())
     ^~
   cc1: some warnings being treated as errors

vim +/if +503 mm/readahead.c

   480	
   481	/**
   482	 * page_cache_sync_readahead - generic file readahead
   483	 * @mapping: address_space which holds the pagecache and I/O vectors
   484	 * @ra: file_ra_state which holds the readahead state
   485	 * @filp: passed on to ->readpage() and ->readpages()
   486	 * @offset: start offset into @mapping, in pagecache page-sized units
   487	 * @req_size: hint: total size of the read which the caller is performing in
   488	 *            pagecache pages
   489	 *
   490	 * page_cache_sync_readahead() should be called when a cache miss happened:
   491	 * it will submit the read.  The readahead logic may decide to piggyback more
   492	 * pages onto the read request if access patterns suggest it will improve
   493	 * performance.
   494	 */
   495	void page_cache_sync_readahead(struct address_space *mapping,
   496				       struct file_ra_state *ra, struct file *filp,
   497				       pgoff_t offset, unsigned long req_size)
   498	{
   499		/* no read-ahead */
   500		if (!ra->ra_pages)
   501			return;
   502	
 > 503		if (blk_cgroup_congested())
   504			return;
   505	
   506		/* be dumb */
   507		if (filp && (filp->f_mode & FMODE_RANDOM)) {
   508			force_page_cache_readahead(mapping, filp, offset, req_size);
   509			return;
   510		}
   511	
   512		/* do read-ahead */
   513		ondemand_readahead(mapping, ra, filp, false, offset, req_size);
   514	}
   515	EXPORT_SYMBOL_GPL(page_cache_sync_readahead);
   516	

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