Re: [PATCH v5 09/20] gfs2: use __bio_add_page for adding single page to bio

[Johannes Thumshirn <Johannes.Thumshirn@wdc.com>]

On 02.05.23 13:51, Bob Peterson wrote:
> On 5/2/23 6:19 AM, Johannes Thumshirn wrote:
>> The GFS2 superblock reading code uses bio_add_page() to add a page to a
>> newly created bio. bio_add_page() can fail, but the return value is never
>> checked.
>>
>> Use __bio_add_page() as adding a single page to a newly created bio is
>> guaranteed to succeed.
>>
>> This brings us a step closer to marking bio_add_page() as __must_check.
>>
>> Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
>> Reviewed-by: Andreas Gruenbacher <agruenba@redhat.com>
>> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
>> ---
>>   fs/gfs2/ops_fstype.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
>> index 9af9ddb61ca0..cd962985b058 100644
>> --- a/fs/gfs2/ops_fstype.c
>> +++ b/fs/gfs2/ops_fstype.c
>> @@ -254,7 +254,7 @@ static int gfs2_read_super(struct gfs2_sbd *sdp, sector_t sector, int silent)
>>   
>>   	bio = bio_alloc(sb->s_bdev, 1, REQ_OP_READ | REQ_META, GFP_NOFS);
>>   	bio->bi_iter.bi_sector = sector * (sb->s_blocksize >> 9);
>> -	bio_add_page(bio, page, PAGE_SIZE, 0);
>> +	__bio_add_page(bio, page, PAGE_SIZE, 0);
>>   
>>   	bio->bi_end_io = end_bio_io_page;
>>   	bio->bi_private = page;
> Hi Johannes,
> 
> So...I see 6 different calls to bio_add_page() in gfs2.
> Why change this particular bio_add_page() to __bio_add_page() and not 
> the other five?
> 

Hi Bob,

Because all the others check the return value of bio_add_page(), only the
one converted doesn't. But it also doesn't need to as we're using 
__bio_add_page() on a newly created bio.