Re: [PATCH] block: Remove the control of complete cpu from bio.

[Tao Ma <tm@tao.ma>]

ping.
For the detailed discussion, please refer to
https://lkml.org/lkml/2011/9/15/98

Thanks
Tao

On 09/16/2011 05:41 PM, Tao Ma wrote:
> From: Tao Ma <boyu.mt@taobao.com>
> 
> bio originally has the functionality to set the complete cpu, but
> it is broken.
> 
> Chirstoph said that "This code is unused, and from the all the
> discussions lately pretty obviously broken.  The only thing keeping
> it serves is creating more confusion and possibly more bugs."
> 
> And Jens replied with "We can kill bio_set_completion_cpu(). I'm fine
> with leaving cpu control to the request based drivers, they are the
> only ones that can toggle the setting anyway".
> 
> So this patch tries to remove all the work of controling complete cpu
> from a bio.
> 
> Cc: Shaohua Li <shaohua.li@intel.com>
> Cc: Christoph Hellwig <hch@infradead.org>
> Cc: Jens Axboe <jaxboe@fusionio.com>
> Signed-off-by: Tao Ma <boyu.mt@taobao.com>
> ---
>  block/blk-core.c          |    4 +---
>  drivers/md/raid1.c        |    1 -
>  fs/bio.c                  |    1 -
>  include/linux/bio.h       |    8 --------
>  include/linux/blk_types.h |   11 ++++-------
>  5 files changed, 5 insertions(+), 20 deletions(-)
> 
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 90e1ffd..8a57916 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -1200,7 +1200,6 @@ out:
>  
>  void init_request_from_bio(struct request *req, struct bio *bio)
>  {
> -	req->cpu = bio->bi_comp_cpu;
>  	req->cmd_type = REQ_TYPE_FS;
>  
>  	req->cmd_flags |= bio->bi_rw & REQ_COMMON_MASK;
> @@ -1281,8 +1280,7 @@ get_rq:
>  	 */
>  	init_request_from_bio(req, bio);
>  
> -	if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) ||
> -	    bio_flagged(bio, BIO_CPU_AFFINE))
> +	if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags))
>  		req->cpu = raw_smp_processor_id();
>  
>  	plug = current->plug;
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index 32323f0..3107bcc 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -2170,7 +2170,6 @@ static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, i
>  		bio->bi_next = NULL;
>  		bio->bi_flags &= ~(BIO_POOL_MASK-1);
>  		bio->bi_flags |= 1 << BIO_UPTODATE;
> -		bio->bi_comp_cpu = -1;
>  		bio->bi_rw = READ;
>  		bio->bi_vcnt = 0;
>  		bio->bi_idx = 0;
> diff --git a/fs/bio.c b/fs/bio.c
> index 9bfade8..41c93c7 100644
> --- a/fs/bio.c
> +++ b/fs/bio.c
> @@ -255,7 +255,6 @@ void bio_init(struct bio *bio)
>  {
>  	memset(bio, 0, sizeof(*bio));
>  	bio->bi_flags = 1 << BIO_UPTODATE;
> -	bio->bi_comp_cpu = -1;
>  	atomic_set(&bio->bi_cnt, 1);
>  }
>  EXPORT_SYMBOL(bio_init);
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index ce33e68..a3c071c 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -269,14 +269,6 @@ extern void bvec_free_bs(struct bio_set *, struct bio_vec *, unsigned int);
>  extern unsigned int bvec_nr_vecs(unsigned short idx);
>  
>  /*
> - * Allow queuer to specify a completion CPU for this bio
> - */
> -static inline void bio_set_completion_cpu(struct bio *bio, unsigned int cpu)
> -{
> -	bio->bi_comp_cpu = cpu;
> -}
> -
> -/*
>   * bio_set is used to allow other portions of the IO system to
>   * allocate their own private memory pools for bio and iovec structures.
>   * These memory pools in turn all allocate from the bio_slab
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index 32f0076..174bc3a 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -59,8 +59,6 @@ struct bio {
>  
>  	unsigned int		bi_max_vecs;	/* max bvl_vecs we can hold */
>  
> -	unsigned int		bi_comp_cpu;	/* completion CPU */
> -
>  	atomic_t		bi_cnt;		/* pin count */
>  
>  	struct bio_vec		*bi_io_vec;	/* the actual vec list */
> @@ -93,11 +91,10 @@ struct bio {
>  #define BIO_BOUNCED	5	/* bio is a bounce bio */
>  #define BIO_USER_MAPPED 6	/* contains user pages */
>  #define BIO_EOPNOTSUPP	7	/* not supported */
> -#define BIO_CPU_AFFINE	8	/* complete bio on same CPU as submitted */
> -#define BIO_NULL_MAPPED 9	/* contains invalid user pages */
> -#define BIO_FS_INTEGRITY 10	/* fs owns integrity data, not block layer */
> -#define BIO_QUIET	11	/* Make BIO Quiet */
> -#define BIO_MAPPED_INTEGRITY 12/* integrity metadata has been remapped */
> +#define BIO_NULL_MAPPED 8	/* contains invalid user pages */
> +#define BIO_FS_INTEGRITY 9	/* fs owns integrity data, not block layer */
> +#define BIO_QUIET	10	/* Make BIO Quiet */
> +#define BIO_MAPPED_INTEGRITY 11/* integrity metadata has been remapped */
>  #define bio_flagged(bio, flag)	((bio)->bi_flags & (1 << (flag)))
>  
>  /*