Hi, John,

Thank you for taking the time to write a review.


John Stoffel [off-list ref] writes:

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"dannyshih" == dannyshih  [off-list ref] writes:

dannyshih> From: Danny Shih [off-list ref]
dannyshih> Porvide a way for stacking block device to re-submit the bio
dannyshih> which sholud be handled firstly.

You're spelling needs to be fixed in these messages.

Sorry for so many spelling errors.

The message should be

"Provide a way for stacking block device to re-submit

the bio which should be handled first."

I will fix it.

dannyshih> Signed-off-by: Danny Shih [off-list ref]
dannyshih> Reviewed-by: Allen Peng [off-list ref]
dannyshih> Reviewed-by: Alex Wu [off-list ref]
dannyshih> ---
dannyshih>  block/blk-core.c       | 44 +++++++++++++++++++++++++++++++++-----------
dannyshih>  include/linux/blkdev.h |  1 +
dannyshih>  2 files changed, 34 insertions(+), 11 deletions(-)

dannyshih> diff --git a/block/blk-core.c b/block/blk-core.c
dannyshih> index 96e5fcd..693dc83 100644
dannyshih> --- a/block/blk-core.c
dannyshih> +++ b/block/blk-core.c
dannyshih> @@ -1031,16 +1031,7 @@ static blk_qc_t __submit_bio_noacct_mq(struct bio *bio)
dannyshih>  	return ret;
dannyshih>  }
  
dannyshih> -/**
dannyshih> - * submit_bio_noacct - re-submit a bio to the block device layer for I/O
dannyshih> - * @bio:  The bio describing the location in memory and on the device.
dannyshih> - *
dannyshih> - * This is a version of submit_bio() that shall only be used for I/O that is
dannyshih> - * resubmitted to lower level drivers by stacking block drivers.  All file
dannyshih> - * systems and other upper level users of the block layer should use
dannyshih> - * submit_bio() instead.
dannyshih> - */
dannyshih> -blk_qc_t submit_bio_noacct(struct bio *bio)
dannyshih> +static blk_qc_t do_submit_bio_noacct(struct bio *bio, bool add_head)
dannyshih>  {
dannyshih>  	if (!submit_bio_checks(bio))
dannyshih>  		return BLK_QC_T_NONE;
dannyshih> @@ -1052,7 +1043,10 @@ blk_qc_t submit_bio_noacct(struct bio *bio)
dannyshih>  	 * it is active, and then process them after it returned.
dannyshih>  	 */
dannyshih>  	if (current->bio_list) {
dannyshih> -		bio_list_add(&current->bio_list[0], bio);
dannyshih> +		if (add_head)
dannyshih> +			bio_list_add_head(&current->bio_list[0], bio);
dannyshih> +		else
dannyshih> +			bio_list_add(&current->bio_list[0], bio);
dannyshih>  		return BLK_QC_T_NONE;
dannyshih>  	}
  
dannyshih> @@ -1060,9 +1054,37 @@ blk_qc_t submit_bio_noacct(struct bio *bio)
dannyshih>  		return __submit_bio_noacct_mq(bio);
dannyshih>  	return __submit_bio_noacct(bio);
dannyshih>  }
dannyshih> +
dannyshih> +/**
dannyshih> + * submit_bio_noacct - re-submit a bio to the block device layer for I/O
dannyshih> + * @bio:  The bio describing the location in memory and on the device.
dannyshih> + *
dannyshih> + * This is a version of submit_bio() that shall only be used for I/O that is
dannyshih> + * resubmitted to lower level drivers by stacking block drivers.  All file
dannyshih> + * systems and other upper level users of the block layer should use
dannyshih> + * submit_bio() instead.
dannyshih> + */
dannyshih> +blk_qc_t submit_bio_noacct(struct bio *bio)
dannyshih> +{
dannyshih> +	return do_submit_bio_noacct(bio, false);
dannyshih> +}
dannyshih>  EXPORT_SYMBOL(submit_bio_noacct);

So why is it named "submit_bio_noacct" when it's supposed to be only
used by layers submitting to lower level drivers.  How can this be
figured out by drivers automatically, so the writed doesn't have to
know about this?

There is no logical change while using submit_bio_noacct() after my 
patch. So I didn't change

the name and the documentation of submit_bio_noacct().

  
dannyshih>  /**
dannyshih> + * submit_bio_noacct - re-submit a bio, which needs to be handle firstly,
dannyshih> + *                     to the block device layer for I/O
dannyshih> + * @bio:  The bio describing the location in memory and on the device.
dannyshih> + *
dannyshih> + * alternative submit_bio_noacct() which add bio to the head of
dannyshih> + * current->bio_list.
dannyshih> + */

Firstly isn't proper english.  Maybe something like:

submit_bio_noacct - re-submit a bio which needs to be handled first
because <reasons> to the block device layer for I/O

But the name still sucks, and the *reason* the bio needs to be handled
differently isn't well explained.

Sorry for the grammar mistake. And I wrote the wrong function name here.

It should be replaced by submit_bio_noacct_add_head.


About the function name, the name of submit_bio_noacct_add_head()

is trying to let drivers know that this is just an alternative version of

submit_bio_noacct(). The only difference is that this function adds bio to

the head of current->bio_list, and submit_bio_noacct() adds it to the tail.


About the documentation, what if I change it like:


"submit_bio_noacct_add_head - re-submit a bio which needs to

be handled first to the block device layer for I/O, because it has

sequential relevance with the bio handling in current ->submit_bio.


Alternative submit_bio_noacct() adds bio to the head of

current->bio_list. To keep bio sequence, this function is used

when a block device splits bio and re-submits the remainder back

to itself. This makes sure that the re-submitted bio will be handle

just after the split part of the original bio."


Thanks for your suggestion.

dannyshih> +blk_qc_t submit_bio_noacct_add_head(struct bio *bio)
dannyshih> +{
dannyshih> +	return do_submit_bio_noacct(bio, true);
dannyshih> +}
dannyshih> +EXPORT_SYMBOL(submit_bio_noacct_add_head);
dannyshih> +
dannyshih> +/**
dannyshih>   * submit_bio - submit a bio to the block device layer for I/O
dannyshih>   * @bio: The &struct bio which describes the I/O
dannyshih>   *
dannyshih> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
dannyshih> index 070de09..b0080d0 100644
dannyshih> --- a/include/linux/blkdev.h
dannyshih> +++ b/include/linux/blkdev.h
dannyshih> @@ -905,6 +905,7 @@ static inline void rq_flush_dcache_pages(struct request *rq)
dannyshih>  extern int blk_register_queue(struct gendisk *disk);
dannyshih>  extern void blk_unregister_queue(struct gendisk *disk);
dannyshih>  blk_qc_t submit_bio_noacct(struct bio *bio);
dannyshih> +blk_qc_t submit_bio_noacct_add_head(struct bio *bio);
dannyshih>  extern void blk_rq_init(struct request_queue *q, struct request *rq);
dannyshih>  extern void blk_put_request(struct request *);
dannyshih>  extern struct request *blk_get_request(struct request_queue *, unsigned int op,
dannyshih> --
dannyshih> 2.7.4

Best Regards,

Danny Shih