Re: [PATCH 0/8] Set bi_rw when alloc bio before call bio_add_page.

[majianpeng <majianpeng@gmail.com>]

On 2012-07-30 23:39 Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Wrote:
>On Mon, Jul 30, 2012 at 03:14:28PM +0800, majianpeng wrote:
>> When exec bio_alloc, the bi_rw is zero.But after calling bio_add_page,
>
>What about submit_bio? That sets the bi_rw as well?
>> it will use bi_rw.
>> Fox example, in functiion __bio_add_page,it will call merge_bvec_fn().
>
>function.
>> The merge_bvec_fn of raid456 will use the bi_rw to judge the merge.
>> >> if ((bvm->bi_rw & 1) == WRITE)
>> >> return biovec->bv_len; /* always allow writes to be mergeable */
>
>So what does that mean? Without this patch what happens?
>
Because bio_alloc, the bi_rw is zero default.But in __bio_add_page, it used bi_rw.
For example: if merge_bvce_fn used bi_rw, but the bi_rw is wrong(if bi_rw is not zero).
So the result may be error.
>> 
>> 
>> Jianpeng Ma (8):
>
>Can you collapse all of this in just one patch?
Sorry, I think those files are not a subsystem.So i should send separately.
>
>>   Evalue bio->bi_rw after calling bio_alloc() and before calling
>
>It is 'evaluate'
>>     bio_add_page().
>>   Evalue bio->bi_rw after calling bio_alloc() and before calling    
>>     bio_add_page().
>>   Evalue bio->bi_rw after calling bio_alloc() and before calling    
>>     bio_add_page().
>>   Evalue bio->bi_rw after calling bio_alloc() and before calling    
>>     bio_add_page().
>>   Evalue bio->bi_rw after calling bio_alloc() and before calling    
>>     bio_add_page().
>>   Evalue bio->bi_rw after calling bio_alloc() and before calling    
>>     bio_add_page().
>>   Evalue bio->bi_rw after calling bio_alloc() and before calling    
>>     bio_add_page().
>>   Evalue bio->bi_rw after calling bio_alloc() and before calling    
>>     bio_add_page().
>> 
>>  block/blk-lib.c                     |    1 +
>>  drivers/block/xen-blkback/blkback.c |    1 +
>
>I am not really sure if that is correct. Does 'submit_bio' not do the
>job properly?
Before call submit_bio, it call bio_add_page.
>
>>  fs/btrfs/check-integrity.c          |    1 +
>>  fs/direct-io.c                      |    1 +
>>  fs/ext4/page-io.c                   |    1 +
>>  fs/jfs/jfs_metapage.c               |    1 +
>>  fs/ocfs2/cluster/heartbeat.c        |    8 +++++---
>>  fs/xfs/xfs_aops.c                   |    2 ++
>>  fs/xfs/xfs_buf.c                    |    1 +
>>  9 files changed, 14 insertions(+), 3 deletions(-)
>> 
>> -- 
>> 1.7.9.5
------------------------------------------------------------------------------
Live Security Virtual Conference
Exclusive live event will cover all the ways today's security and 
threat landscape has changed and how IT managers can respond. Discussions 
will include endpoint security, mobile security and the latest in malware 
threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/