Re: [PATCH v2 3/7] btrfs: Convert end_compressed_writeback() to use filemap_get_folios()

[David Sterba]

On Tue, Aug 16, 2022 at 10:52:42AM -0700, Vishal Moola (Oracle) wrote:
> Converted function to use folios throughout. This is in preparation for
> the removal of find_get_pages_contig(). Now also supports large folios.
> 
> Since we may receive more than nr_pages pages, nr_pages may underflow.
> Since nr_pages > 0 is equivalent to index <= end_index, we replaced it
> with this check instead.
> 
> Also this function does not care about the pages being contiguous so we
> can just use filemap_get_folios() to be more efficient.
> 
> Signed-off-by: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>

With minor comments

Acked-by: David Sterba <dsterba@xxxxxxxx>

> --- a/fs/btrfs/compression.c
> +++ b/fs/btrfs/compression.c
> @@ -8,6 +8,7 @@
>  #include <linux/file.h>
>  #include <linux/fs.h>
>  #include <linux/pagemap.h>
> +#include <linux/pagevec.h>
>  #include <linux/highmem.h>
>  #include <linux/kthread.h>
>  #include <linux/time.h>
> @@ -339,8 +340,7 @@ static noinline void end_compressed_writeback(struct inode *inode,
>  	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
>  	unsigned long index = cb->start >> PAGE_SHIFT;
>  	unsigned long end_index = (cb->start + cb->len - 1) >> PAGE_SHIFT;
> -	struct page *pages[16];
> -	unsigned long nr_pages = end_index - index + 1;
> +	struct folio_batch fbatch;
>  	const int errno = blk_status_to_errno(cb->status);
>  	int i;
>  	int ret;
> @@ -348,24 +348,22 @@ static noinline void end_compressed_writeback(struct inode *inode,
>  	if (errno)
>  		mapping_set_error(inode->i_mapping, errno);
>  
> -	while (nr_pages > 0) {
> -		ret = find_get_pages_contig(inode->i_mapping, index,
> -				     min_t(unsigned long,
> -				     nr_pages, ARRAY_SIZE(pages)), pages);
> +	folio_batch_init(&fbatch);
> +	while (index <= end_index) {
> +		ret = filemap_get_folios(inode->i_mapping, &index, end_index,
> +				&fbatch);
> +
>  		if (ret == 0) {
> -			nr_pages -= 1;
> -			index += 1;
> -			continue;
> +			return;
>  		}

Please drop { } around single statement

>  		for (i = 0; i < ret; i++) {
> +			struct folio *folio = fbatch.folios[i];

And add a newline after declaration.

>  			if (errno)
> -				SetPageError(pages[i]);
> -			btrfs_page_clamp_clear_writeback(fs_info, pages[i],
> +				folio_set_error(folio);
> +			btrfs_page_clamp_clear_writeback(fs_info, &folio->page,
>  							 cb->start, cb->len);
> -			put_page(pages[i]);
>  		}
> -		nr_pages -= ret;
> -		index += ret;
> +		folio_batch_release(&fbatch);
>  	}
>  	/* the inode may be gone now */
>  }
> -- 
> 2.36.1