On Thu, Oct 29, 2020 at 07:33:53PM +0000, Matthew Wilcox (Oracle) wrote:
> Add mapping_get_read_heads() which returns the head pages which
> represent a contiguous array of bytes in the file. It also stops
> when encountering a page marked as Readahead or !Uptodate (but
> does return that page) so it can be handled appropriately by
> gfbr_get_pages().
I don't like the _heads naming - this is like find_get_pages_contig() except it
returns compound pages instead of single pages, and the naming should reflect
that. And, working with compound pages should be the default in the future -
code working with individual pages should be considered a code smell in the
future, i.e. find_get_pages() et. all. should be considered deprecated.
We have the same issue in the block layer with multi page bvecs where the naming
really should be better; the more complicated name should be for the unusual
case, which is not what we have now.
Also - you're implementing new core functionality with a pecularity of the read
path, the two probably be split out. Perhaps find_get_cpages (compound_pages)
that can also be passed a stop condition.
Not all of this is necessarily for this patch, but perhaps a comment indicating
where we want to go in the future would be helpful.
> - if (writably_mapped)
> - flush_dcache_page(pages[i]);
> + if (writably_mapped) {
> + int j;
> +
> + for (j = 0; j < thp_nr_pages(page); j++)
> + flush_dcache_page(page + j);
> + }
this should be a new helper
