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

On 2012-07-30 23:39 Konrad Rzeszutek Wilk [off-list ref] Wrote:

On Mon, Jul 30, 2012 at 03:14:28PM +0800, majianpeng wrote:

quoted

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?

quoted

it will use bi_rw.
Fox example, in functiion __bio_add_page,it will call merge_bvec_fn().

function.

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The merge_bvec_fn of raid456 will use the bi_rw to judge the merge.

quoted

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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.

quoted

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.

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  Evalue bio->bi_rw after calling bio_alloc() and before calling

It is 'evaluate'

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    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.

quoted

 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

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