linux-kernel - Re: [PATCH]:drivers/md/raid10.c: r10buf_pool_alloc(): Set bi

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Message-ID: <20110714134228.65fb79c5@notabene.brown>
Date:	Thu, 14 Jul 2011 13:42:28 +1000
From:	NeilBrown <neilb@...e.de>
To:	Muthu Kumar <muthu.lkml@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH]:drivers/md/raid10.c: r10buf_pool_alloc(): Set bi_vcnt
 for the new bio.

On Tue, 12 Jul 2011 17:50:32 -0700 Muthu Kumar <muthu.lkml@...il.com> wrote:

> Hi Neil,
> raid10.c: r10buf_pool_alloc() - doesn't set the bi_vcnt for the newly
> allocated bio. Setting it to RESYNC_PAGES for successful case.

What would be the point of doing that?  When an r10buf allocated in
sync_request(), one of the first things done to it is to initialise it
including setting bi_vcnt to 0.

> 
> BTW, why are we not using bio_add_page() here to add the page to bio?

How would that be useful?  We don't know what the underlying device is at
this point, and the point of bio_add_page is to make sure the device can
handle the extra page.

We do call bio_add_page at the appropriate time in sync_request().

So - not applied.

Thanks,
NeilBrown

> 
> Signed-off-by: Muthukumar R <muthur@...il.com>
> 
> ------
>  drivers/md/raid10.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> ------
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index 6e84668..8504c5b 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -129,6 +129,7 @@ static void * r10buf_pool_alloc(gfp_t gfp_flags, void *data)
> 
>                         bio->bi_io_vec[i].bv_page = page;
>                 }
> +               bio->bi_vcnt = RESYNC_PAGES;
>         }
> 
>         return r10_bio;
> --
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