Re: [PATCH 4/4] block_dev: support RFW_NOWAIT on block device nodes

Hi Christoph,

[auto build test WARNING on linus/master]
[also build test WARNING on next-20170707]
[cannot apply to v4.12]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Christoph-Hellwig/fs-pass-iocb-to-do_generic_file_read/20170708-020747
config: x86_64-randconfig-x012-201727 (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All warnings (new ones prefixed by >>):

   In file included from include/linux/init.h:4:0,
                    from fs/block_dev.c:8:
   fs/block_dev.c: In function 'blkdev_write_iter':
   fs/block_dev.c:1895:21: warning: suggest parentheses around comparison in operand of '&' [-Wparentheses]
     if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_DIRECT) == IOCB_NOWAIT)
                        ^
   include/linux/compiler.h:156:30: note: in definition of macro '__trace_if'
     if (__builtin_constant_p(!!(cond)) ? !!(cond) :   \
                                 ^~~~

quoted

fs/block_dev.c:1895:2: note: in expansion of macro 'if'

     if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_DIRECT) == IOCB_NOWAIT)
     ^~
   fs/block_dev.c:1895:21: warning: suggest parentheses around comparison in operand of '&' [-Wparentheses]
     if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_DIRECT) == IOCB_NOWAIT)
                        ^
   include/linux/compiler.h:156:42: note: in definition of macro '__trace_if'
     if (__builtin_constant_p(!!(cond)) ? !!(cond) :   \
                                             ^~~~

quoted

fs/block_dev.c:1895:2: note: in expansion of macro 'if'

     if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_DIRECT) == IOCB_NOWAIT)
     ^~
   fs/block_dev.c:1895:21: warning: suggest parentheses around comparison in operand of '&' [-Wparentheses]
     if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_DIRECT) == IOCB_NOWAIT)
                        ^
   include/linux/compiler.h:167:16: note: in definition of macro '__trace_if'
      ______r = !!(cond);     \
                   ^~~~

quoted

fs/block_dev.c:1895:2: note: in expansion of macro 'if'

     if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_DIRECT) == IOCB_NOWAIT)
     ^~

vim +/if +1895 fs/block_dev.c

  1879	{
  1880		struct file *file = iocb->ki_filp;
  1881		struct inode *bd_inode = bdev_file_inode(file);
  1882		loff_t size = i_size_read(bd_inode);
  1883		struct blk_plug plug;
  1884		ssize_t ret;
  1885	
  1886		if (bdev_read_only(I_BDEV(bd_inode)))
  1887			return -EPERM;
  1888	
  1889		if (!iov_iter_count(from))
  1890			return 0;
  1891	
  1892		if (iocb->ki_pos >= size)
  1893			return -ENOSPC;
  1894	

1895		if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_DIRECT) == IOCB_NOWAIT)

  1896			return -EOPNOTSUPP;
  1897	
  1898		iov_iter_truncate(from, size - iocb->ki_pos);
  1899	
  1900		blk_start_plug(&plug);
  1901		ret = __generic_file_write_iter(iocb, from);
  1902		if (ret > 0)
  1903			ret = generic_write_sync(iocb, ret);

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