Re: [RFC 0/4] convert create_page_buffers to create_folio_buffers

Hannes Reinecke
2023-04-17T06:04:48Z

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
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