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    SubjectRe: [PATCH v14 011/138] mm/lru: Add folio LRU functions
    On Thu, Jul 15, 2021 at 04:34:57AM +0100, Matthew Wilcox (Oracle) wrote:
    > Handle arbitrary-order folios being added to the LRU. By definition,
    > all pages being added to the LRU were already head or base pages, but
    > call page_folio() on them anyway to get the type right and avoid the
    > buried calls to compound_head().
    >
    > Saves 783 bytes of kernel text; no functions grow.
    >
    > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
    > Reviewed-by: Yu Zhao <yuzhao@google.com>
    > Reviewed-by: Christoph Hellwig <hch@lst.de>
    > Reviewed-by: David Howells <dhowells@redhat.com>
    > Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    > ---
    > include/linux/mm_inline.h | 98 ++++++++++++++++++++++------------
    > include/trace/events/pagemap.h | 2 +-
    > 2 files changed, 65 insertions(+), 35 deletions(-)

    Acked-by: Mike Rapoport <rppt@linux.ibm.com>

    > diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
    > index 355ea1ee32bd..ee155d19885e 100644
    > --- a/include/linux/mm_inline.h
    > +++ b/include/linux/mm_inline.h
    > @@ -6,22 +6,27 @@
    > #include <linux/swap.h>
    >
    > /**
    > - * page_is_file_lru - should the page be on a file LRU or anon LRU?
    > - * @page: the page to test
    > + * folio_is_file_lru - should the folio be on a file LRU or anon LRU?
    > + * @folio: the folio to test
    > *
    > - * Returns 1 if @page is a regular filesystem backed page cache page or a lazily
    > - * freed anonymous page (e.g. via MADV_FREE). Returns 0 if @page is a normal
    > - * anonymous page, a tmpfs page or otherwise ram or swap backed page. Used by
    > - * functions that manipulate the LRU lists, to sort a page onto the right LRU
    > - * list.
    > + * Returns 1 if @folio is a regular filesystem backed page cache folio
    > + * or a lazily freed anonymous folio (e.g. via MADV_FREE). Returns 0 if
    > + * @folio is a normal anonymous folio, a tmpfs folio or otherwise ram or
    > + * swap backed folio. Used by functions that manipulate the LRU lists,
    > + * to sort a folio onto the right LRU list.
    > *
    > * We would like to get this info without a page flag, but the state
    > - * needs to survive until the page is last deleted from the LRU, which
    > + * needs to survive until the folio is last deleted from the LRU, which
    > * could be as far down as __page_cache_release.

    It seems mm_inline.h is not a part of generated API docs, otherwise
    kerneldoc would be unhappy about missing Return: description.

    > */
    > +static inline int folio_is_file_lru(struct folio *folio)
    > +{
    > + return !folio_test_swapbacked(folio);
    > +}
    > +
    > static inline int page_is_file_lru(struct page *page)
    > {
    > - return !PageSwapBacked(page);
    > + return folio_is_file_lru(page_folio(page));
    > }
    >
    > static __always_inline void update_lru_size(struct lruvec *lruvec,
    > @@ -39,69 +44,94 @@ static __always_inline void update_lru_size(struct lruvec *lruvec,
    > }
    >
    > /**
    > - * __clear_page_lru_flags - clear page lru flags before releasing a page
    > - * @page: the page that was on lru and now has a zero reference
    > + * __folio_clear_lru_flags - clear page lru flags before releasing a page
    > + * @folio: The folio that was on lru and now has a zero reference
    > */
    > -static __always_inline void __clear_page_lru_flags(struct page *page)
    > +static __always_inline void __folio_clear_lru_flags(struct folio *folio)
    > {
    > - VM_BUG_ON_PAGE(!PageLRU(page), page);
    > + VM_BUG_ON_FOLIO(!folio_test_lru(folio), folio);
    >
    > - __ClearPageLRU(page);
    > + __folio_clear_lru(folio);
    >
    > /* this shouldn't happen, so leave the flags to bad_page() */
    > - if (PageActive(page) && PageUnevictable(page))
    > + if (folio_test_active(folio) && folio_test_unevictable(folio))
    > return;
    >
    > - __ClearPageActive(page);
    > - __ClearPageUnevictable(page);
    > + __folio_clear_active(folio);
    > + __folio_clear_unevictable(folio);
    > +}
    > +
    > +static __always_inline void __clear_page_lru_flags(struct page *page)
    > +{
    > + __folio_clear_lru_flags(page_folio(page));
    > }
    >
    > /**
    > - * page_lru - which LRU list should a page be on?
    > - * @page: the page to test
    > + * folio_lru_list - which LRU list should a folio be on?
    > + * @folio: the folio to test
    > *
    > - * Returns the LRU list a page should be on, as an index
    > + * Returns the LRU list a folio should be on, as an index

    ^ Return:

    > * into the array of LRU lists.
    > */
    > -static __always_inline enum lru_list page_lru(struct page *page)
    > +static __always_inline enum lru_list folio_lru_list(struct folio *folio)
    > {
    > enum lru_list lru;
    >
    > - VM_BUG_ON_PAGE(PageActive(page) && PageUnevictable(page), page);
    > + VM_BUG_ON_FOLIO(folio_test_active(folio) && folio_test_unevictable(folio), folio);
    >
    > - if (PageUnevictable(page))
    > + if (folio_test_unevictable(folio))
    > return LRU_UNEVICTABLE;
    >
    > - lru = page_is_file_lru(page) ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON;
    > - if (PageActive(page))
    > + lru = folio_is_file_lru(folio) ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON;
    > + if (folio_test_active(folio))
    > lru += LRU_ACTIVE;
    >
    > return lru;
    > }

    . . .

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