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    SubjectRe: [PATCH v3 17/25] mm: Add __page_cache_alloc_order
    On Wed, Apr 29, 2020 at 6:37 AM Matthew Wilcox <willy@infradead.org> wrote:
    >
    > From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
    >
    > This new function allows page cache pages to be allocated that are
    > larger than an order-0 page.
    >
    > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
    > Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    > ---
    > include/linux/pagemap.h | 24 +++++++++++++++++++++---
    > mm/filemap.c | 12 ++++++++----
    > 2 files changed, 29 insertions(+), 7 deletions(-)
    >
    > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
    > index 55199cb5bd66..1169e2428dd7 100644
    > --- a/include/linux/pagemap.h
    > +++ b/include/linux/pagemap.h
    > @@ -205,15 +205,33 @@ static inline int page_cache_add_speculative(struct page *page, int count)
    > return __page_cache_add_speculative(page, count);
    > }
    >
    > +static inline gfp_t thp_gfpmask(gfp_t gfp)
    > +{
    > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
    > + /* We'd rather allocate smaller pages than stall a page fault */
    > + gfp |= GFP_TRANSHUGE_LIGHT;

    This looks not correct. GFP_TRANSHUGE_LIGHT may set GFP_FS, but some
    filesystem may expect GFP_NOFS, i.e. in readahead path.

    > + gfp &= ~__GFP_DIRECT_RECLAIM;
    > +#endif
    > + return gfp;
    > +}
    > +
    > #ifdef CONFIG_NUMA
    > -extern struct page *__page_cache_alloc(gfp_t gfp);
    > +extern struct page *__page_cache_alloc_order(gfp_t gfp, unsigned int order);
    > #else
    > -static inline struct page *__page_cache_alloc(gfp_t gfp)
    > +static inline
    > +struct page *__page_cache_alloc_order(gfp_t gfp, unsigned int order)
    > {
    > - return alloc_pages(gfp, 0);
    > + if (order == 0)
    > + return alloc_pages(gfp, 0);
    > + return prep_transhuge_page(alloc_pages(thp_gfpmask(gfp), order));
    > }
    > #endif
    >
    > +static inline struct page *__page_cache_alloc(gfp_t gfp)
    > +{
    > + return __page_cache_alloc_order(gfp, 0);
    > +}
    > +
    > static inline struct page *page_cache_alloc(struct address_space *x)
    > {
    > return __page_cache_alloc(mapping_gfp_mask(x));
    > diff --git a/mm/filemap.c b/mm/filemap.c
    > index 23a051a7ef0f..9abba062973a 100644
    > --- a/mm/filemap.c
    > +++ b/mm/filemap.c
    > @@ -941,24 +941,28 @@ int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
    > EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
    >
    > #ifdef CONFIG_NUMA
    > -struct page *__page_cache_alloc(gfp_t gfp)
    > +struct page *__page_cache_alloc_order(gfp_t gfp, unsigned int order)
    > {
    > int n;
    > struct page *page;
    >
    > + if (order > 0)
    > + gfp = thp_gfpmask(gfp);
    > +
    > if (cpuset_do_page_mem_spread()) {
    > unsigned int cpuset_mems_cookie;
    > do {
    > cpuset_mems_cookie = read_mems_allowed_begin();
    > n = cpuset_mem_spread_node();
    > - page = __alloc_pages_node(n, gfp, 0);
    > + page = __alloc_pages_node(n, gfp, order);
    > + prep_transhuge_page(page);
    > } while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
    >
    > return page;
    > }
    > - return alloc_pages(gfp, 0);
    > + return prep_transhuge_page(alloc_pages(gfp, order));
    > }
    > -EXPORT_SYMBOL(__page_cache_alloc);
    > +EXPORT_SYMBOL(__page_cache_alloc_order);
    > #endif
    >
    > /*
    > --
    > 2.26.2
    >
    >

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