Re: [PATCH -next] zram: do not pass rw argument to __zram_make_request()

[Minchan Kim <minchan@kernel.org>]

On Thu, Jan 09, 2014 at 04:23:43PM +0300, Sergey Senozhatsky wrote:
> Do not pass rw argument down the __zram_make_request() -> zram_bvec_rw()
> chain, decode it in zram_bvec_rw() instead. Besides, this is the place
> where we distinguish READ and WRITE bio data directions, so account zram
> RW stats here, instead of __zram_make_request(). This also allows to
> account a real number of zram READ/WRITE operations, not just requests
> (RW request may end up in a number of zram RW ops with separate
> locking, compression/decompression, slot free handling, etc).

Looks sane to me because other statistic variable accounts per bio, not
request. But it changes current statistic's semantic so they could be
regressed. Let's wait a bit for other's opinion.

Thanks.


> 
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> 
> ---
> 
>  drivers/block/zram/zram_drv.c | 29 ++++++++++++-----------------
>  1 file changed, 12 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 833d24f..798793f 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -534,22 +534,27 @@ static void handle_pending_slot_free(struct zram *zram)
>  }
>  
>  static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
> -			int offset, struct bio *bio, int rw)
> +			int offset, struct bio *bio)
>  {
>  	int ret;
> +	int rw = bio_data_dir(bio);
> +
> +	if (rw == READA)
> +		rw = READ;
>  
>  	if (rw == READ) {
> +		atomic64_inc(&zram->stats.num_reads);
>  		down_read(&zram->lock);
>  		handle_pending_slot_free(zram);
>  		ret = zram_bvec_read(zram, bvec, index, offset, bio);
>  		up_read(&zram->lock);
>  	} else {
> +		atomic64_inc(&zram->stats.num_writes);
>  		down_write(&zram->lock);
>  		handle_pending_slot_free(zram);
>  		ret = zram_bvec_write(zram, bvec, index, offset);
>  		up_write(&zram->lock);
>  	}
> -
>  	return ret;
>  }
>  
> @@ -680,22 +685,13 @@ out:
>  	return ret;
>  }
>  
> -static void __zram_make_request(struct zram *zram, struct bio *bio, int rw)
> +static void __zram_make_request(struct zram *zram, struct bio *bio)
>  {
>  	int offset;
>  	u32 index;
>  	struct bio_vec bvec;
>  	struct bvec_iter iter;
>  
> -	switch (rw) {
> -	case READ:
> -		atomic64_inc(&zram->stats.num_reads);
> -		break;
> -	case WRITE:
> -		atomic64_inc(&zram->stats.num_writes);
> -		break;
> -	}
> -
>  	index = bio->bi_iter.bi_sector >> SECTORS_PER_PAGE_SHIFT;
>  	offset = (bio->bi_iter.bi_sector &
>  		  (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT;
> @@ -714,16 +710,15 @@ static void __zram_make_request(struct zram *zram, struct bio *bio, int rw)
>  			bv.bv_len = max_transfer_size;
>  			bv.bv_offset = bvec.bv_offset;
>  
> -			if (zram_bvec_rw(zram, &bv, index, offset, bio, rw) < 0)
> +			if (zram_bvec_rw(zram, &bv, index, offset, bio) < 0)
>  				goto out;
>  
>  			bv.bv_len = bvec.bv_len - max_transfer_size;
>  			bv.bv_offset += max_transfer_size;
> -			if (zram_bvec_rw(zram, &bv, index+1, 0, bio, rw) < 0)
> +			if (zram_bvec_rw(zram, &bv, index + 1, 0, bio) < 0)
>  				goto out;
>  		} else
> -			if (zram_bvec_rw(zram, &bvec, index, offset, bio, rw)
> -			    < 0)
> +			if (zram_bvec_rw(zram, &bvec, index, offset, bio) < 0)
>  				goto out;
>  
>  		update_position(&index, &offset, &bvec);
> @@ -753,7 +748,7 @@ static void zram_make_request(struct request_queue *queue, struct bio *bio)
>  		goto error;
>  	}
>  
> -	__zram_make_request(zram, bio, bio_data_dir(bio));
> +	__zram_make_request(zram, bio);
>  	up_read(&zram->init_lock);
>  
>  	return;
> --
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-- 
Kind regards,
Minchan Kim