Re: [RFC 2/8] fs/mpage: avoid negative shift for large blocksize

[Matthew Wilcox <willy@xxxxxxxxxxxxx>]

On Wed, Nov 13, 2024 at 01:47:21AM -0800, Luis Chamberlain wrote:
> +++ b/fs/mpage.c
> @@ -181,7 +181,7 @@ static struct bio *do_mpage_readpage(struct mpage_readpage_args *args)
>  	if (folio_buffers(folio))
>  		goto confused;
>  
> -	block_in_file = (sector_t)folio->index << (PAGE_SHIFT - blkbits);
> +	block_in_file = (sector_t)(((loff_t)folio->index << PAGE_SHIFT) >> blkbits);

	block_in_file = folio_pos(folio) >> blkbits;
?

> @@ -527,7 +527,7 @@ static int __mpage_writepage(struct folio *folio, struct writeback_control *wbc,
>  	 * The page has no buffers: map it to disk
>  	 */
>  	BUG_ON(!folio_test_uptodate(folio));
> -	block_in_file = (sector_t)folio->index << (PAGE_SHIFT - blkbits);
> +	block_in_file = (sector_t)(((loff_t)folio->index << PAGE_SHIFT) >> blkbits);

Likewise.