Messages in this thread | | | Date | Wed, 12 Feb 2020 09:52:50 -0800 | From | Christoph Hellwig <> | Subject | Re: [PATCH v2 02/25] mm: Optimise find_subpage for !THP |
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On Wed, Feb 12, 2020 at 05:02:00AM -0800, Matthew Wilcox wrote: > > Can you add comments describing the use case of this function and why > > it does all these checks? It looks like black magic to me. > > Would this help? > > -static inline struct page *find_subpage(struct page *page, pgoff_t offset) > +/* > + * Given the page we found in the page cache, return the page corresponding > + * to this offset in the file > + */ > +static inline struct page *find_subpage(struct page *head, pgoff_t offset) > { > - if (PageHuge(page)) > - return page; > + /* HugeTLBfs wants the head page regardless */ > + if (PageHuge(head)) > + return head; > > - VM_BUG_ON_PAGE(PageTail(page), page); > + VM_BUG_ON_PAGE(PageTail(head), head); > > - return page + (offset & (hpage_nr_pages(page) - 1)); > + return head + (offset & (hpage_nr_pages(head) - 1));
Much better.
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