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From: Ming Lei <tom.leiming@gmail.com>
To: Christoph Hellwig <hch@lst.de>
Cc: "open list:XFS FILESYSTEM" <linux-xfs@vger.kernel.org>,
	Linux FS Devel <linux-fsdevel@vger.kernel.org>,
	linux-block <linux-block@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>
Subject: Re: [PATCH 01/33] block: add a lower-level bio_add_page interface
Date: Thu, 10 May 2018 16:52:00 +0800
Message-ID: <CACVXFVMPwQV8M0raTcLUtqDix-kEkYV3E3fJSVOVw8m=iiv5Uw@mail.gmail.com> (raw)
In-Reply-To: <20180509074830.16196-2-hch@lst.de>

On Wed, May 9, 2018 at 3:47 PM, Christoph Hellwig <hch@lst.de> wrote:
> For the upcoming removal of buffer heads in XFS we need to keep track of
> the number of outstanding writeback requests per page.  For this we need
> to know if bio_add_page merged a region with the previous bvec or not.
> Instead of adding additional arguments this refactors bio_add_page to
> be implemented using three lower level helpers which users like XFS can
> use directly if they care about the merge decisions.

The merge policy may be transparent to fs, such as multipage bvec.

>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  block/bio.c         | 87 ++++++++++++++++++++++++++++++---------------
>  include/linux/bio.h |  9 +++++
>  2 files changed, 67 insertions(+), 29 deletions(-)
>
> diff --git a/block/bio.c b/block/bio.c
> index 53e0f0a1ed94..6ceba6adbf42 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -773,7 +773,7 @@ int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page
>                         return 0;
>         }
>
> -       if (bio->bi_vcnt >= bio->bi_max_vecs)
> +       if (bio_full(bio))
>                 return 0;
>
>         /*
> @@ -820,6 +820,59 @@ int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page
>  }
>  EXPORT_SYMBOL(bio_add_pc_page);
>
> +/**
> + * __bio_try_merge_page - try adding data to an existing bvec
> + * @bio: destination bio
> + * @page: page to add
> + * @len: length of the range to add
> + * @off: offset into @page
> + *
> + * Try adding the data described at @page + @offset to the last bvec of @bio.
> + * Return %true on success or %false on failure.  This can happen frequently
> + * for file systems with a block size smaller than the page size.
> + */
> +bool __bio_try_merge_page(struct bio *bio, struct page *page,
> +               unsigned int len, unsigned int off)
> +{
> +       if (bio->bi_vcnt > 0) {
> +               struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
> +
> +               if (page == bv->bv_page && off == bv->bv_offset + bv->bv_len) {
> +                       bv->bv_len += len;
> +                       bio->bi_iter.bi_size += len;
> +                       return true;
> +               }
> +       }
> +       return false;
> +}
> +EXPORT_SYMBOL_GPL(__bio_try_merge_page);
> +
> +/**
> + * __bio_add_page - add page to a bio in a new segment
> + * @bio: destination bio
> + * @page: page to add
> + * @len: length of the range to add
> + * @off: offset into @page
> + *
> + * Add the data at @page + @offset to @bio as a new bvec.  The caller must
> + * ensure that @bio has space for another bvec.
> + */
> +void __bio_add_page(struct bio *bio, struct page *page,
> +               unsigned int len, unsigned int off)
> +{
> +       struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt];
> +
> +       WARN_ON_ONCE(bio_full(bio));
> +
> +       bv->bv_page = page;
> +       bv->bv_offset = off;
> +       bv->bv_len = len;
> +
> +       bio->bi_iter.bi_size += len;
> +       bio->bi_vcnt++;
> +}
> +EXPORT_SYMBOL_GPL(__bio_add_page);

Given both __bio_try_merge_page() and __bio_add_page() are exported,
please add WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)), otherwise
both may be misused by external users.

-- 
Ming Lei

  parent reply index

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-09  7:47 stop using buffer heads in xfs and iomap Christoph Hellwig
2018-05-09  7:47 ` [PATCH 01/33] block: add a lower-level bio_add_page interface Christoph Hellwig
2018-05-09 15:12   ` Matthew Wilcox
2018-05-10  6:40     ` Christoph Hellwig
2018-05-10 21:49       ` Andreas Dilger
2018-05-11  6:29         ` Christoph Hellwig
2018-05-15 16:47           ` Jens Axboe
2018-05-10  8:52   ` Ming Lei [this message]
2018-05-11  6:24     ` Christoph Hellwig
2018-05-16  5:06   ` Ritesh Harjani
2018-05-16 18:05     ` Christoph Hellwig
2018-05-17  4:18       ` Ritesh Harjani
2018-05-09  7:47 ` [PATCH 02/33] fs: factor out a __generic_write_end helper Christoph Hellwig
2018-05-09 15:15   ` Matthew Wilcox
2018-05-10  6:40     ` Christoph Hellwig
2018-05-09  7:48 ` [PATCH 03/33] fs: move page_cache_seek_hole_data to iomap.c Christoph Hellwig
2018-05-09  7:48 ` [PATCH 04/33] fs: remove the buffer_unwritten check in page_seek_hole_data Christoph Hellwig
2018-05-17 11:33   ` Andreas Grünbacher
2018-05-09  7:48 ` [PATCH 05/33] fs: use ->is_partially_uptodate in page_cache_seek_hole_data Christoph Hellwig
2018-05-09  7:48 ` [PATCH 06/33] mm: give the 'ret' variable a better name __do_page_cache_readahead Christoph Hellwig
2018-05-09 15:45   ` Matthew Wilcox
2018-05-10  6:41     ` Christoph Hellwig
2018-05-09  7:48 ` [PATCH 07/33] mm: split ->readpages calls to avoid non-contiguous pages lists Christoph Hellwig
2018-05-09 15:46   ` Matthew Wilcox
2018-05-09  7:48 ` [PATCH 08/33] iomap: use __bio_add_page in iomap_dio_zero Christoph Hellwig
2018-05-09  7:48 ` [PATCH 09/33] iomap: add a iomap_sector helper Christoph Hellwig
2018-05-09  7:48 ` [PATCH 10/33] iomap: add an iomap-based bmap implementation Christoph Hellwig
2018-05-09 16:46   ` Darrick J. Wong
2018-05-10  6:42     ` Christoph Hellwig
2018-05-10 15:08       ` Darrick J. Wong
2018-05-11  6:25         ` Christoph Hellwig
2018-05-12  1:56           ` Darrick J. Wong
2018-05-09  7:48 ` [PATCH 11/33] iomap: add an iomap-based readpage and readpages implementation Christoph Hellwig
2018-05-10  1:17   ` Dave Chinner
2018-05-10  6:44     ` Christoph Hellwig
2018-05-09  7:48 ` [PATCH 12/33] xfs: use iomap_bmap Christoph Hellwig
2018-05-09  7:48 ` [PATCH 13/33] xfs: use iomap for blocksize == PAGE_SIZE readpage and readpages Christoph Hellwig
2018-05-09  7:48 ` [PATCH 14/33] xfs: simplify xfs_bmap_punch_delalloc_range Christoph Hellwig
2018-05-09  7:48 ` [PATCH 15/33] xfs: simplify xfs_aops_discard_page Christoph Hellwig
2018-05-09  7:48 ` [PATCH 16/33] xfs: move locking into xfs_bmap_punch_delalloc_range Christoph Hellwig
2018-05-09  7:48 ` [PATCH 17/33] xfs: make xfs_writepage_map extent map centric Christoph Hellwig
2018-05-09  7:48 ` [PATCH 18/33] xfs: remove the now unused XFS_BMAPI_IGSTATE flag Christoph Hellwig
2018-05-09  7:48 ` [PATCH 19/33] xfs: remove xfs_reflink_find_cow_mapping Christoph Hellwig
2018-05-09  7:48 ` [PATCH 20/33] xfs: remove xfs_reflink_trim_irec_to_next_cow Christoph Hellwig
2018-05-09  7:48 ` [PATCH 21/33] xfs: simplify xfs_map_blocks by using xfs_iext_lookup_extent directly Christoph Hellwig
2018-05-09  7:48 ` [PATCH 22/33] xfs: don't clear imap_valid for a non-uptodate buffers Christoph Hellwig
2018-05-09  7:48 ` [PATCH 23/33] xfs: remove the imap_valid flag Christoph Hellwig
2018-05-09  7:48 ` [PATCH 24/33] xfs: don't look at buffer heads in xfs_add_to_ioend Christoph Hellwig
2018-05-09  7:48 ` [PATCH 25/33] xfs: move all writeback buffer_head manipulation into xfs_map_at_offset Christoph Hellwig
2018-05-09  7:48 ` [PATCH 26/33] xfs: allow writeback on pages without buffer heads Christoph Hellwig
2018-05-09  7:48 ` [PATCH 27/33] xfs: remove xfs_start_page_writeback Christoph Hellwig
2018-05-09  7:48 ` [PATCH 28/33] xfs: refactor the tail of xfs_writepage_map Christoph Hellwig
2018-05-09  7:48 ` [PATCH 29/33] xfs: do not set the page uptodate in xfs_writepage_map Christoph Hellwig
2018-05-09  7:48 ` [PATCH 30/33] iomap: add initial support for writes without buffer heads Christoph Hellwig
2018-05-09  7:48 ` [PATCH 31/33] iomap: add support for sub-pagesize buffered I/O " Christoph Hellwig
2018-05-14 16:00   ` Goldwyn Rodrigues
2018-05-15  7:26     ` Christoph Hellwig
2018-05-15 13:47       ` Goldwyn Rodrigues
2018-05-16  5:46         ` Dave Chinner
2018-05-09  7:48 ` [PATCH 32/33] xfs: add support for sub-pagesize writeback without buffer_heads Christoph Hellwig
2018-05-09  7:48 ` [PATCH 33/33] fs: remove __block_write_begin and iomap_to_bh Christoph Hellwig
2018-05-10 15:13 ` stop using buffer heads in xfs and iomap Darrick J. Wong
2018-05-11  6:22   ` Christoph Hellwig
2018-05-11  6:39     ` Darrick J. Wong

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