linux-kernel - Re: [RFC 0/4] convert create_page_buffers to create_folio

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Date:   Sun, 16 Apr 2023 19:27:18 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Hannes Reinecke <hare@...e.de>
Cc:     Pankaj Raghav <p.raghav@...sung.com>, brauner@...nel.org,
        willy@...radead.org, viro@...iv.linux.org.uk,
        akpm@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, gost.dev@...sung.com
Subject: Re: [RFC 0/4] convert create_page_buffers to create_folio_buffers

On Fri, Apr 14, 2023 at 03:47:13PM +0200, Hannes Reinecke wrote:
> @@ -2333,13 +2395,15 @@ int block_read_full_folio(struct folio *folio,
> get_block_t *get_block)
>         if (IS_ENABLED(CONFIG_FS_VERITY) && IS_VERITY(inode))
>                 limit = inode->i_sb->s_maxbytes;
> 
> -       VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
> -
>         head = create_folio_buffers(folio, inode, 0);
>         blocksize = head->b_size;
>         bbits = block_size_bits(blocksize);
> 
> -       iblock = (sector_t)folio->index << (PAGE_SHIFT - bbits);
> +       if (WARN_ON(PAGE_SHIFT < bbits)) {
> +               iblock = (sector_t)folio->index >> (bbits - PAGE_SHIFT);
> +       } else {
> +               iblock = (sector_t)folio->index << (PAGE_SHIFT - bbits);
> +       }
>         lblock = (limit+blocksize-1) >> bbits;
>         bh = head;
>         nr = 0;

BTW I See this pattern in:

fs/mpage.c: do_mpage_readpage()
fs/mpage.c: __mpage_writepage()

A helper might be in order.

  Luis