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Date:   Mon, 17 Apr 2023 08:04:42 +0200
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Subject: Re: [RFC 0/4] convert create_page_buffers to create_folio_buffers
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To:     Luis Chamberlain <mcgrof@kernel.org>
Cc:     Pankaj Raghav <p.raghav@samsung.com>, brauner@kernel.org,
        willy@infradead.org, viro@zeniv.linux.org.uk,
        akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, gost.dev@samsung.com
References: <CGME20230414110825eucas1p1ed4d16627889ef8542dfa31b1183063d@eucas1p1.samsung.com>
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 <1e68a118-d177-a218-5139-c8f13793dbbf@suse.de>
 <ZDyuhmcc9OeJGUcJ@bombadil.infradead.org>
From:   Hannes Reinecke <hare@suse.de>
In-Reply-To: <ZDyuhmcc9OeJGUcJ@bombadil.infradead.org>
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On 4/17/23 04:27, Luis Chamberlain wrote:
> 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.
> 

But only _iff_ we decide to stick with buffer_heads and upgrade the 
buffer_head code to handle multi-page block sizes.
The idea was to move over to iomap, hence I'm not sure into which
lengths we should go keeping buffer_heads alive ...

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
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