Re: [PATCH v2 25/28] iomap: Convert iomap_add_to_ioend() to take a folio

["Darrick J. Wong" <djwong@kernel.org>]

On Mon, Nov 08, 2021 at 04:05:48AM +0000, Matthew Wilcox (Oracle) wrote:
> We still iterate one block at a time, but now we call compound_head()
> less often.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Looks good!
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
>  fs/iomap/buffered-io.c | 70 ++++++++++++++++++++----------------------
>  1 file changed, 34 insertions(+), 36 deletions(-)
> 
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index b168cc0fe8be..90f9f33ffe41 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -1249,29 +1249,29 @@ iomap_can_add_to_ioend(struct iomap_writepage_ctx *wpc, loff_t offset,
>   * first; otherwise finish off the current ioend and start another.
>   */
>  static void
> -iomap_add_to_ioend(struct inode *inode, loff_t offset, struct page *page,
> +iomap_add_to_ioend(struct inode *inode, loff_t pos, struct folio *folio,
>  		struct iomap_page *iop, struct iomap_writepage_ctx *wpc,
>  		struct writeback_control *wbc, struct list_head *iolist)
>  {
> -	sector_t sector = iomap_sector(&wpc->iomap, offset);
> +	sector_t sector = iomap_sector(&wpc->iomap, pos);
>  	unsigned len = i_blocksize(inode);
> -	unsigned poff = offset & (PAGE_SIZE - 1);
> +	size_t poff = offset_in_folio(folio, pos);
>  
> -	if (!wpc->ioend || !iomap_can_add_to_ioend(wpc, offset, sector)) {
> +	if (!wpc->ioend || !iomap_can_add_to_ioend(wpc, pos, sector)) {
>  		if (wpc->ioend)
>  			list_add(&wpc->ioend->io_list, iolist);
> -		wpc->ioend = iomap_alloc_ioend(inode, wpc, offset, sector, wbc);
> +		wpc->ioend = iomap_alloc_ioend(inode, wpc, pos, sector, wbc);
>  	}
>  
> -	if (bio_add_page(wpc->ioend->io_bio, page, len, poff) != len) {
> +	if (!bio_add_folio(wpc->ioend->io_bio, folio, len, poff)) {
>  		wpc->ioend->io_bio = iomap_chain_bio(wpc->ioend->io_bio);
> -		__bio_add_page(wpc->ioend->io_bio, page, len, poff);
> +		bio_add_folio(wpc->ioend->io_bio, folio, len, poff);
>  	}
>  
>  	if (iop)
>  		atomic_add(len, &iop->write_bytes_pending);
>  	wpc->ioend->io_size += len;
> -	wbc_account_cgroup_owner(wbc, page, len);
> +	wbc_account_cgroup_owner(wbc, &folio->page, len);
>  }
>  
>  /*
> @@ -1293,9 +1293,8 @@ iomap_add_to_ioend(struct inode *inode, loff_t offset, struct page *page,
>  static int
>  iomap_writepage_map(struct iomap_writepage_ctx *wpc,
>  		struct writeback_control *wbc, struct inode *inode,
> -		struct page *page, u64 end_pos)
> +		struct folio *folio, u64 end_pos)
>  {
> -	struct folio *folio = page_folio(page);
>  	struct iomap_page *iop = iomap_page_create(inode, folio);
>  	struct iomap_ioend *ioend, *next;
>  	unsigned len = i_blocksize(inode);
> @@ -1322,15 +1321,15 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
>  			continue;
>  		if (wpc->iomap.type == IOMAP_HOLE)
>  			continue;
> -		iomap_add_to_ioend(inode, pos, page, iop, wpc, wbc,
> +		iomap_add_to_ioend(inode, pos, folio, iop, wpc, wbc,
>  				 &submit_list);
>  		count++;
>  	}
>  
>  	WARN_ON_ONCE(!wpc->ioend && !list_empty(&submit_list));
> -	WARN_ON_ONCE(!PageLocked(page));
> -	WARN_ON_ONCE(PageWriteback(page));
> -	WARN_ON_ONCE(PageDirty(page));
> +	WARN_ON_ONCE(!folio_test_locked(folio));
> +	WARN_ON_ONCE(folio_test_writeback(folio));
> +	WARN_ON_ONCE(folio_test_dirty(folio));
>  
>  	/*
>  	 * We cannot cancel the ioend directly here on error.  We may have
> @@ -1348,14 +1347,14 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
>  		if (wpc->ops->discard_folio)
>  			wpc->ops->discard_folio(folio, pos);
>  		if (!count) {
> -			ClearPageUptodate(page);
> -			unlock_page(page);
> +			folio_clear_uptodate(folio);
> +			folio_unlock(folio);
>  			goto done;
>  		}
>  	}
>  
> -	set_page_writeback(page);
> -	unlock_page(page);
> +	folio_start_writeback(folio);
> +	folio_unlock(folio);
>  
>  	/*
>  	 * Preserve the original error if there was one; catch
> @@ -1376,9 +1375,9 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
>  	 * with a partial page truncate on a sub-page block sized filesystem.
>  	 */
>  	if (!count)
> -		end_page_writeback(page);
> +		folio_end_writeback(folio);
>  done:
> -	mapping_set_error(page->mapping, error);
> +	mapping_set_error(folio->mapping, error);
>  	return error;
>  }
>  
> @@ -1392,14 +1391,15 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
>  static int
>  iomap_do_writepage(struct page *page, struct writeback_control *wbc, void *data)
>  {
> +	struct folio *folio = page_folio(page);
>  	struct iomap_writepage_ctx *wpc = data;
> -	struct inode *inode = page->mapping->host;
> +	struct inode *inode = folio->mapping->host;
>  	u64 end_pos, isize;
>  
> -	trace_iomap_writepage(inode, page_offset(page), PAGE_SIZE);
> +	trace_iomap_writepage(inode, folio_pos(folio), folio_size(folio));
>  
>  	/*
> -	 * Refuse to write the page out if we're called from reclaim context.
> +	 * Refuse to write the folio out if we're called from reclaim context.
>  	 *
>  	 * This avoids stack overflows when called from deeply used stacks in
>  	 * random callers for direct reclaim or memcg reclaim.  We explicitly
> @@ -1413,10 +1413,10 @@ iomap_do_writepage(struct page *page, struct writeback_control *wbc, void *data)
>  		goto redirty;
>  
>  	/*
> -	 * Is this page beyond the end of the file?
> +	 * Is this folio beyond the end of the file?
>  	 *
> -	 * The page index is less than the end_index, adjust the end_offset
> -	 * to the highest offset that this page should represent.
> +	 * The folio index is less than the end_index, adjust the end_pos
> +	 * to the highest offset that this folio should represent.
>  	 * -----------------------------------------------------
>  	 * |			file mapping	       | <EOF> |
>  	 * -----------------------------------------------------
> @@ -1426,7 +1426,7 @@ iomap_do_writepage(struct page *page, struct writeback_control *wbc, void *data)
>  	 * ---------------------------------^------------------|
>  	 */
>  	isize = i_size_read(inode);
> -	end_pos = page_offset(page) + PAGE_SIZE;
> +	end_pos = folio_pos(folio) + folio_size(folio);
>  	if (end_pos > isize) {
>  		/*
>  		 * Check whether the page to write out is beyond or straddles
> @@ -1439,7 +1439,7 @@ iomap_do_writepage(struct page *page, struct writeback_control *wbc, void *data)
>  		 * |				    |      Straddles     |
>  		 * ---------------------------------^-----------|--------|
>  		 */
> -		size_t poff = offset_in_page(isize);
> +		size_t poff = offset_in_folio(folio, isize);
>  		pgoff_t end_index = isize >> PAGE_SHIFT;
>  
>  		/*
> @@ -1459,8 +1459,8 @@ iomap_do_writepage(struct page *page, struct writeback_control *wbc, void *data)
>  		 * checking if the page is totally beyond i_size or if its
>  		 * offset is just equal to the EOF.
>  		 */
> -		if (page->index > end_index ||
> -		    (page->index == end_index && poff == 0))
> +		if (folio->index > end_index ||
> +		    (folio->index == end_index && poff == 0))
>  			goto redirty;
>  
>  		/*
> @@ -1471,17 +1471,15 @@ iomap_do_writepage(struct page *page, struct writeback_control *wbc, void *data)
>  		 * memory is zeroed when mapped, and writes to that region are
>  		 * not written out to the file."
>  		 */
> -		zero_user_segment(page, poff, PAGE_SIZE);
> -
> -		/* Adjust the end_offset to the end of file */
> +		folio_zero_segment(folio, poff, folio_size(folio));
>  		end_pos = isize;
>  	}
>  
> -	return iomap_writepage_map(wpc, wbc, inode, page, end_pos);
> +	return iomap_writepage_map(wpc, wbc, inode, folio, end_pos);
>  
>  redirty:
> -	redirty_page_for_writepage(wbc, page);
> -	unlock_page(page);
> +	folio_redirty_for_writepage(wbc, folio);
> +	folio_unlock(folio);
>  	return 0;
>  }
>  
> -- 
> 2.33.0
>