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From: Ming Lei <[email protected]>
To: Pavel Begunkov <[email protected]>
Cc: [email protected], Jens Axboe <[email protected]>,
	Christoph Hellwig <[email protected]>,
	Matthew Wilcox <[email protected]>,
	Johannes Weiner <[email protected]>,
	Alexander Viro <[email protected]>,
	"Darrick J . Wong" <[email protected]>,
	"Martin K . Petersen" <[email protected]>,
	Jonathan Corbet <[email protected]>,
	[email protected], [email protected],
	[email protected], [email protected],
	[email protected], [email protected],
	[email protected], Christoph Hellwig <[email protected]>
Subject: Re: [PATCH v3 6/7] bio: add a helper calculating nr segments to alloc
Date: Mon, 11 Jan 2021 10:57:10 +0800	[thread overview]
Message-ID: <20210111025710.GG4147870@T590> (raw)
In-Reply-To: <cde94f6cc32bd8a899129575678c4195f7cb187b.1610170479.git.asml.silence@gmail.com>

On Sat, Jan 09, 2021 at 04:03:02PM +0000, Pavel Begunkov wrote:
> Add a helper function calculating the number of bvec segments we need to
> allocate to construct a bio. It doesn't change anything functionally,
> but will be used to not duplicate special cases in the future.
> 
> Reviewed-by: Christoph Hellwig <[email protected]>
> Signed-off-by: Pavel Begunkov <[email protected]>
> ---
>  fs/block_dev.c       |  7 ++++---
>  fs/iomap/direct-io.c |  9 ++++-----
>  include/linux/bio.h  | 10 ++++++++++
>  3 files changed, 18 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 3b8963e228a1..6f5bd9950baf 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -416,7 +416,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
>  		dio->size += bio->bi_iter.bi_size;
>  		pos += bio->bi_iter.bi_size;
>  
> -		nr_pages = iov_iter_npages(iter, BIO_MAX_PAGES);
> +		nr_pages = bio_iov_vecs_to_alloc(iter, BIO_MAX_PAGES);
>  		if (!nr_pages) {
>  			bool polled = false;
>  
> @@ -481,9 +481,10 @@ blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
>  {
>  	int nr_pages;
>  
> -	nr_pages = iov_iter_npages(iter, BIO_MAX_PAGES + 1);
> -	if (!nr_pages)
> +	if (!iov_iter_count(iter))
>  		return 0;
> +
> +	nr_pages = bio_iov_vecs_to_alloc(iter, BIO_MAX_PAGES + 1);
>  	if (is_sync_kiocb(iocb) && nr_pages <= BIO_MAX_PAGES)
>  		return __blkdev_direct_IO_simple(iocb, iter, nr_pages);
>  
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index 933f234d5bec..ea1e8f696076 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -250,11 +250,8 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
>  	orig_count = iov_iter_count(dio->submit.iter);
>  	iov_iter_truncate(dio->submit.iter, length);
>  
> -	nr_pages = iov_iter_npages(dio->submit.iter, BIO_MAX_PAGES);
> -	if (nr_pages <= 0) {
> -		ret = nr_pages;
> +	if (!iov_iter_count(dio->submit.iter))
>  		goto out;
> -	}
>  
>  	if (need_zeroout) {
>  		/* zero out from the start of the block to the write offset */
> @@ -263,6 +260,7 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
>  			iomap_dio_zero(dio, iomap, pos - pad, pad);
>  	}
>  
> +	nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter, BIO_MAX_PAGES);
>  	do {
>  		size_t n;
>  		if (dio->error) {
> @@ -308,7 +306,8 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
>  		dio->size += n;
>  		copied += n;
>  
> -		nr_pages = iov_iter_npages(dio->submit.iter, BIO_MAX_PAGES);
> +		nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter,
> +						 BIO_MAX_PAGES);
>  		iomap_dio_submit_bio(dio, iomap, bio, pos);
>  		pos += n;
>  	} while (nr_pages);
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index 1edda614f7ce..d8f9077c43ef 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -10,6 +10,7 @@
>  #include <linux/ioprio.h>
>  /* struct bio, bio_vec and BIO_* flags are defined in blk_types.h */
>  #include <linux/blk_types.h>
> +#include <linux/uio.h>
>  
>  #define BIO_DEBUG
>  
> @@ -441,6 +442,15 @@ static inline void bio_wouldblock_error(struct bio *bio)
>  	bio_endio(bio);
>  }
>  
> +/*
> + * Calculate number of bvec segments that should be allocated to fit data
> + * pointed by @iter.
> + */
> +static inline int bio_iov_vecs_to_alloc(struct iov_iter *iter, int max_segs)
> +{
> +	return iov_iter_npages(iter, max_segs);
> +}
> +
>  struct request_queue;
>  
>  extern int submit_bio_wait(struct bio *bio);
> -- 
> 2.24.0
> 

Reviewed-by: Ming Lei <[email protected]>

-- 
Ming


  reply	other threads:[~2021-01-11  2:58 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-09 16:02 [PATCH v3 0/7] no-copy bvec Pavel Begunkov
2021-01-09 16:02 ` [PATCH v3 1/7] splice: don't generate zero-len segement bvecs Pavel Begunkov
2021-01-11  2:48   ` Ming Lei
2021-01-09 16:02 ` [PATCH v3 2/7] bvec/iter: disallow zero-length segment bvecs Pavel Begunkov
2021-01-11  2:49   ` Ming Lei
2021-01-09 16:02 ` [PATCH v3 3/7] block/psi: remove PSI annotations from direct IO Pavel Begunkov
2021-01-11  2:52   ` Ming Lei
2021-01-09 16:03 ` [PATCH v3 4/7] target/file: allocate the bvec array as part of struct target_core_file_cmd Pavel Begunkov
2021-01-11  2:53   ` Ming Lei
2021-01-09 16:03 ` [PATCH v3 5/7] iov_iter: optimise bvec iov_iter_advance() Pavel Begunkov
2021-01-11  2:55   ` Ming Lei
2021-01-09 16:03 ` [PATCH v3 6/7] bio: add a helper calculating nr segments to alloc Pavel Begunkov
2021-01-11  2:57   ` Ming Lei [this message]
2021-01-09 16:03 ` [PATCH v3 7/7] bio: don't copy bvec for direct IO Pavel Begunkov
2021-01-11  3:00   ` Ming Lei
2021-01-25 15:58 ` [PATCH v3 0/7] no-copy bvec Jens Axboe

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