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

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Date:   Fri, 14 Apr 2023 17:00:19 +0200
From:   Pankaj Raghav <p.raghav@...sung.com>
To:     Hannes Reinecke <hare@...e.de>, <brauner@...nel.org>,
        <willy@...radead.org>, <viro@...iv.linux.org.uk>,
        <akpm@...ux-foundation.org>
CC:     <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <mcgrof@...nel.org>, <gost.dev@...sung.com>
Subject: Re: [RFC 0/4] convert create_page_buffers to create_folio_buffers

>> Pankaj Raghav (4):
>>    fs/buffer: add set_bh_folio helper
>>    buffer: add alloc_folio_buffers() helper
>>    fs/buffer: add folio_create_empty_buffers helper
>>    fs/buffer: convert create_page_buffers to create_folio_buffers
>>
>>   fs/buffer.c                 | 131 +++++++++++++++++++++++++++++++++---
>>   include/linux/buffer_head.h |   4 ++
>>   2 files changed, 125 insertions(+), 10 deletions(-)
>>
> Funnily enough, I've been tinkering along the same lines, and ended up with pretty similar patches.
> I've had to use two additional patches to get my modified 'brd' driver off the ground with logical
> blocksize of 16k:

Good to know that we are working on a similar direction here.

> - mm/filemap: allocate folios according to the blocksize
>   (will be sending the patch separately)
> - Modify read_folio() to use the correct order:
> 
> @@ -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;
> 
> 
> With that (and my modified brd driver) I've been able to set the logical blocksize to 16k for brd
> and have it happily loaded.

I will give your patches a try as well.