Re: [RFC PATCH v3 01/18] block: Add check for async buffered writes to generic_write_checks

[Stefan Roesch <shr@fb.com>]

On 5/19/22 1:17 AM, Christoph Hellwig wrote:
> On Wed, May 18, 2022 at 04:36:52PM -0700, Stefan Roesch wrote:
>> @@ -1633,7 +1633,9 @@ int generic_write_checks_count(struct kiocb *iocb, loff_t *count)
>>  	if (iocb->ki_flags & IOCB_APPEND)
>>  		iocb->ki_pos = i_size_read(inode);
>>  
>> -	if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))
>> +	if ((iocb->ki_flags & IOCB_NOWAIT) &&
>> +		!((iocb->ki_flags & IOCB_DIRECT) ||
>> +		  (file->f_mode & FMODE_BUF_WASYNC)))
> 
> This is some really odd indentation.  I'd expect something like:
> 
> 	if ((iocb->ki_flags & IOCB_NOWAIT) &&
> 	    !((iocb->ki_flags & IOCB_DIRECT) ||
> 	      (file->f_mode & FMODE_BUF_WASYNC)))
> 

I reformatted the above code for the next version.

>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>> index bbde95387a23..3b479d02e210 100644
>> --- a/include/linux/fs.h
>> +++ b/include/linux/fs.h
>> @@ -177,6 +177,9 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
>>  /* File supports async buffered reads */
>>  #define FMODE_BUF_RASYNC	((__force fmode_t)0x40000000)
>>  
>> +/* File supports async nowait buffered writes */
>> +#define FMODE_BUF_WASYNC	((__force fmode_t)0x80000000)
> 
> This is the last available flag in fmode_t.
> 
> At some point we should probably move the static capabilities to
> a member of file_operations.