Re: [PATCH v2 1/8] fs/buffer: simplify block_read_full_folio() with bh_offset()

Hannes Reinecke
2025-02-05T16:18:23Z

On 2/5/25 00:12, Luis Chamberlain wrote:
> When we read over all buffers in a folio we currently use the
> buffer index on the folio and blocksize to get the offset. Simplify
> this with bh_offset(). This simplifies the loop while making no
> functional changes.
>
> Suggested-by: Matthew Wilcox <willy@infradead.org>
> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
> ---
> fs/buffer.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/fs/buffer.c b/fs/buffer.c
> index cc8452f60251..b99560e8a142 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -2381,7 +2381,6 @@ int block_read_full_folio(struct folio *folio, get_block_t *get_block)
> lblock = div_u64(limit + blocksize - 1, blocksize);
> bh = head;
> nr = 0;
> - i = 0;
>
> do {
> if (buffer_uptodate(bh))
> @@ -2398,7 +2397,7 @@ int block_read_full_folio(struct folio *folio, get_block_t *get_block)
> page_error = true;
> }
> if (!buffer_mapped(bh)) {
> - folio_zero_range(folio, i * blocksize,
> + folio_zero_range(folio, bh_offset(bh),
> blocksize);
> if (!err)
> set_buffer_uptodate(bh);
> @@ -2412,7 +2411,7 @@ int block_read_full_folio(struct folio *folio, get_block_t *get_block)
> continue;
> }
> arr[nr++] = bh;
> - } while (i++, iblock++, (bh = bh->b_this_page) != head);
> + } while (iblock++, (bh = bh->b_this_page) != head);
>
> if (fully_mapped)
> folio_set_mappedtodisk(folio);

One wonders: shouldn't we use plugging here to make I/O more efficient?

Cheers,

Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@suse.de +49 911 74053 688
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