Re: [PATCH 1/3] mpage: mpage_readpages() should submit IO as read-ahead

[Jens Axboe <axboe@kernel.dk>]

On 5/24/18 1:43 PM, Andrew Morton wrote:
> On Thu, 24 May 2018 10:02:52 -0600 Jens Axboe <axboe@kernel.dk> wrote:
> 
>> a_ops->readpages() is only ever used for read-ahead, yet we don't
>> flag the IO being submitted as such. Fix that up. Any file system
>> that uses mpage_readpages() as it's ->readpages() implementation
>> will now get this right.
>>
>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
>> ---
>>  fs/mpage.c | 17 +++++++++--------
>>  1 file changed, 9 insertions(+), 8 deletions(-)
>>
>> diff --git a/fs/mpage.c b/fs/mpage.c
>> index b7e7f570733a..0a5474237f5e 100644
>> --- a/fs/mpage.c
>> +++ b/fs/mpage.c
>> @@ -146,7 +146,7 @@ static struct bio *
>>  do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
>>  		sector_t *last_block_in_bio, struct buffer_head *map_bh,
>>  		unsigned long *first_logical_block, get_block_t get_block,
>> -		gfp_t gfp)
>> +		gfp_t gfp, bool is_readahead)
> 
> That's a lot of arguments.
> 
> I suspect we'll have a faster kernel if we mark this __always_inline. 
> I think my ancient "This isn't called much at all" over
> mpage_readpage() remains true.  Almost all callers come in via
> mpage_readpages(), which would benefit from the inlining.  But mpage.o
> gets 1.5k fatter.  hm.

Was going to send out a v2, but would be nice to get some consensus on
what you prefer here. I can either do the struct version, or I can
keep it as-is (going from 8 to 9 arguments). For the struct version,
I'd prefer to do that as a prep patch, so the functional change is
clear.

-- 
Jens Axboe