Messages in this thread | | | Date | Wed, 13 Feb 2019 15:41:02 +0100 | From | Jan Kara <> | Subject | Re: [PATCH v2] page cache: Store only head pages in i_pages |
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On Tue 12-02-19 10:34:54, Matthew Wilcox wrote: > Transparent Huge Pages are currently stored in i_pages as pointers to > consecutive subpages. This patch changes that to storing consecutive > pointers to the head page in preparation for storing huge pages more > efficiently in i_pages. > > Large parts of this are "inspired" by Kirill's patch > https://lore.kernel.org/lkml/20170126115819.58875-2-kirill.shutemov@linux.intel.com/ > > Signed-off-by: Matthew Wilcox <willy@infradead.org>
I like the idea!
> @@ -1778,33 +1767,27 @@ unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start, > > rcu_read_lock(); > xas_for_each(&xas, page, end) { > - struct page *head; > if (xas_retry(&xas, page)) > continue; > /* Skip over shadow, swap and DAX entries */ > if (xa_is_value(page)) > continue; > > - head = compound_head(page); > - if (!page_cache_get_speculative(head)) > + if (!page_cache_get_speculative(page)) > goto retry; > > - /* The page was split under us? */ > - if (compound_head(page) != head) > - goto put_page; > - > - /* Has the page moved? */ > + /* Has the page moved or been split? */ > if (unlikely(page != xas_reload(&xas))) > goto put_page; > > - pages[ret] = page; > + pages[ret] = find_subpage(page, xas.xa_index); > if (++ret == nr_pages) { > *start = page->index + 1; > goto out; > }
So this subtly changes the behavior because now we will be returning in '*start' a different index. So you should rather use 'pages[ret]->index' instead.
> @@ -1923,26 +1899,21 @@ unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index, > if (xa_is_value(page)) > continue; > > - head = compound_head(page); > - if (!page_cache_get_speculative(head)) > + if (!page_cache_get_speculative(page)) > goto retry; > > - /* The page was split under us? */ > - if (compound_head(page) != head) > - goto put_page; > - > - /* Has the page moved? */ > + /* Has the page moved or been split? */ > if (unlikely(page != xas_reload(&xas))) > goto put_page; > > - pages[ret] = page; > + pages[ret] = find_subpage(page, xas.xa_index); > if (++ret == nr_pages) { > *index = page->index + 1; > goto out; > }
Ditto here.
Otherwise the patch looks good to me so feel free to add:
Acked-by: Jan Kara <jack@suse.cz>
after fixing these two.
Honza -- Jan Kara <jack@suse.com> SUSE Labs, CR
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