Re: [PATCH v5 04/11] readahead: allocate folios with mapping_min_order in readahead

[Hannes Reinecke <hare@suse.de>]

On 5/3/24 11:53, Luis Chamberlain wrote:
> From: Pankaj Raghav <p.raghav@samsung.com>
> 
> page_cache_ra_unbounded() was allocating single pages (0 order folios)
> if there was no folio found in an index. Allocate mapping_min_order folios
> as we need to guarantee the minimum order if it is set.
> When read_pages() is triggered and if a page is already present, check
> for truncation and move the ractl->_index by mapping_min_nrpages if that
> folio was truncated. This is done to ensure we keep the alignment
> requirement while adding a folio to the page cache.
> 
> page_cache_ra_order() tries to allocate folio to the page cache with a
> higher order if the index aligns with that order. Modify it so that the
> order does not go below the mapping_min_order requirement of the page
> cache. This function will do the right thing even if the new_order passed
> is less than the mapping_min_order.
> When adding new folios to the page cache we must also ensure the index
> used is aligned to the mapping_min_order as the page cache requires the
> index to be aligned to the order of the folio.
> 
> readahead_expand() is called from readahead aops to extend the range of
> the readahead so this function can assume ractl->_index to be aligned with
> min_order.
> 
> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
> ---
>   mm/readahead.c | 85 +++++++++++++++++++++++++++++++++++++++++---------
>   1 file changed, 71 insertions(+), 14 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
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