Re: [PATCH 2/8] btrfs: track the next file offset in struct btrfs_bio_ctrl

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

在 2025/4/9 20:40, Christoph Hellwig 写道:
> Stop poking into bio implementation details and recalculating the pos
> from the folio over and over and instead just track then end of the
> current bio in logical file offsets in the btrfs_bio_ctrl.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Qu Wenruo <wqu@suse.com>

Thanks,
Qu> ---
>   fs/btrfs/extent_io.c | 33 +++++++++++++--------------------
>   1 file changed, 13 insertions(+), 20 deletions(-)
>
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 193736b07a0b..36db23f7a6bb 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -96,6 +96,7 @@ void btrfs_extent_buffer_leak_debug_check(struct btrfs_fs_info *fs_info)
>    */
>   struct btrfs_bio_ctrl {
>   	struct btrfs_bio *bbio;
> +	loff_t next_file_offset; /* last byte contained in bbio + 1 */
>   	enum btrfs_compression_type compress_type;
>   	u32 len_to_oe_boundary;
>   	blk_opf_t opf;
> @@ -643,13 +644,10 @@ static int alloc_eb_folio_array(struct extent_buffer *eb, bool nofail)
>   }
>
>   static bool btrfs_bio_is_contig(struct btrfs_bio_ctrl *bio_ctrl,
> -				struct folio *folio, u64 disk_bytenr,
> -				unsigned int pg_offset)
> +				u64 disk_bytenr, loff_t file_offset)
>   {
>   	struct bio *bio = &bio_ctrl->bbio->bio;
> -	struct bio_vec *bvec = bio_last_bvec_all(bio);
>   	const sector_t sector = disk_bytenr >> SECTOR_SHIFT;
> -	struct folio *bv_folio = page_folio(bvec->bv_page);
>
>   	if (bio_ctrl->compress_type != BTRFS_COMPRESS_NONE) {
>   		/*
> @@ -660,19 +658,11 @@ static bool btrfs_bio_is_contig(struct btrfs_bio_ctrl *bio_ctrl,
>   	}
>
>   	/*
> -	 * The contig check requires the following conditions to be met:
> -	 *
> -	 * 1) The folios are belonging to the same inode
> -	 *    This is implied by the call chain.
> -	 *
> -	 * 2) The range has adjacent logical bytenr
> -	 *
> -	 * 3) The range has adjacent file offset
> -	 *    This is required for the usage of btrfs_bio->file_offset.
> +	 * To merge into a bio both the disk sector and the logical offset in
> +	 * the file need to be contiguous.
>   	 */
> -	return bio_end_sector(bio) == sector &&
> -		folio_pos(bv_folio) + bvec->bv_offset + bvec->bv_len ==
> -		folio_pos(folio) + pg_offset;
> +	return bio_ctrl->next_file_offset == file_offset &&
> +		bio_end_sector(bio) == sector;
>   }
>
>   static void alloc_new_bio(struct btrfs_inode *inode,
> @@ -690,6 +680,7 @@ static void alloc_new_bio(struct btrfs_inode *inode,
>   	bbio->file_offset = file_offset;
>   	bio_ctrl->bbio = bbio;
>   	bio_ctrl->len_to_oe_boundary = U32_MAX;
> +	bio_ctrl->next_file_offset = file_offset;
>
>   	/* Limit data write bios to the ordered boundary. */
>   	if (bio_ctrl->wbc) {
> @@ -731,12 +722,13 @@ static void submit_extent_folio(struct btrfs_bio_ctrl *bio_ctrl,
>   			       size_t size, unsigned long pg_offset)
>   {
>   	struct btrfs_inode *inode = folio_to_inode(folio);
> +	loff_t file_offset = folio_pos(folio) + pg_offset;
>
>   	ASSERT(pg_offset + size <= folio_size(folio));
>   	ASSERT(bio_ctrl->end_io_func);
>
>   	if (bio_ctrl->bbio &&
> -	    !btrfs_bio_is_contig(bio_ctrl, folio, disk_bytenr, pg_offset))
> +	    !btrfs_bio_is_contig(bio_ctrl, disk_bytenr, file_offset))
>   		submit_one_bio(bio_ctrl);
>
>   	do {
> @@ -745,7 +737,7 @@ static void submit_extent_folio(struct btrfs_bio_ctrl *bio_ctrl,
>   		/* Allocate new bio if needed */
>   		if (!bio_ctrl->bbio) {
>   			alloc_new_bio(inode, bio_ctrl, disk_bytenr,
> -				      folio_pos(folio) + pg_offset);
> +				      file_offset);
>   		}
>
>   		/* Cap to the current ordered extent boundary if there is one. */
> @@ -760,14 +752,15 @@ static void submit_extent_folio(struct btrfs_bio_ctrl *bio_ctrl,
>   			submit_one_bio(bio_ctrl);
>   			continue;
>   		}
> +		bio_ctrl->next_file_offset += len;
>
>   		if (bio_ctrl->wbc)
> -			wbc_account_cgroup_owner(bio_ctrl->wbc, folio,
> -						 len);
> +			wbc_account_cgroup_owner(bio_ctrl->wbc, folio, len);
>
>   		size -= len;
>   		pg_offset += len;
>   		disk_bytenr += len;
> +		file_offset += len;
>
>   		/*
>   		 * len_to_oe_boundary defaults to U32_MAX, which isn't folio or