On Sun, 25 Dec 2016, Nicholas Piggin wrote: > A page is not added to the swap cache without being swap backed, > so PageSwapBacked mappings can use PG_owner_priv_1 for PageSwapCache. > > Acked-by: Hugh Dickins <[email protected]>
Yes, confirmed, Acked-by: Hugh Dickins <[email protected]> I checked through your migrate and memory-failure additions, and both look correct to me. I still think that more should be done for KPF_SWAPCACHE, to exclude the new false positives; but as I said before, no urgency, that can be a later followup. > Signed-off-by: Nicholas Piggin <[email protected]> > --- > include/linux/page-flags.h | 24 ++++++++++++++++-------- > include/trace/events/mmflags.h | 1 - > mm/memory-failure.c | 4 +--- > mm/migrate.c | 14 ++++++++------ > 4 files changed, 25 insertions(+), 18 deletions(-) > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index 74e4dda91238..a57c909a15e4 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -87,7 +87,6 @@ enum pageflags { > PG_private_2, /* If pagecache, has fs aux data */ > PG_writeback, /* Page is under writeback */ > PG_head, /* A head page */ > - PG_swapcache, /* Swap page: swp_entry_t in private */ > PG_mappedtodisk, /* Has blocks allocated on-disk */ > PG_reclaim, /* To be reclaimed asap */ > PG_swapbacked, /* Page is backed by RAM/swap */ > @@ -110,6 +109,9 @@ enum pageflags { > /* Filesystems */ > PG_checked = PG_owner_priv_1, > > + /* SwapBacked */ > + PG_swapcache = PG_owner_priv_1, /* Swap page: swp_entry_t in private */ > + > /* Two page bits are conscripted by FS-Cache to maintain local caching > * state. These bits are set on pages belonging to the netfs's inodes > * when those inodes are being locally cached. > @@ -314,7 +316,13 @@ PAGEFLAG_FALSE(HighMem) > #endif > > #ifdef CONFIG_SWAP > -PAGEFLAG(SwapCache, swapcache, PF_NO_COMPOUND) > +static __always_inline int PageSwapCache(struct page *page) > +{ > + return PageSwapBacked(page) && test_bit(PG_swapcache, &page->flags); > + > +} > +SETPAGEFLAG(SwapCache, swapcache, PF_NO_COMPOUND) > +CLEARPAGEFLAG(SwapCache, swapcache, PF_NO_COMPOUND) > #else > PAGEFLAG_FALSE(SwapCache) > #endif > @@ -701,12 +709,12 @@ static inline void ClearPageSlabPfmemalloc(struct page > *page) > * Flags checked when a page is freed. Pages being freed should not have > * these flags set. It they are, there is a problem. > */ > -#define PAGE_FLAGS_CHECK_AT_FREE \ > - (1UL << PG_lru | 1UL << PG_locked | \ > - 1UL << PG_private | 1UL << PG_private_2 | \ > - 1UL << PG_writeback | 1UL << PG_reserved | \ > - 1UL << PG_slab | 1UL << PG_swapcache | 1UL << PG_active | \ > - 1UL << PG_unevictable | __PG_MLOCKED) > +#define PAGE_FLAGS_CHECK_AT_FREE \ > + (1UL << PG_lru | 1UL << PG_locked | \ > + 1UL << PG_private | 1UL << PG_private_2 | \ > + 1UL << PG_writeback | 1UL << PG_reserved | \ > + 1UL << PG_slab | 1UL << PG_active | \ > + 1UL << PG_unevictable | __PG_MLOCKED) > > /* > * Flags checked when a page is prepped for return by the page allocator. > diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h > index 5a81ab48a2fb..30c2adbdebe8 100644 > --- a/include/trace/events/mmflags.h > +++ b/include/trace/events/mmflags.h > @@ -95,7 +95,6 @@ > {1UL << PG_private_2, "private_2" }, \ > {1UL << PG_writeback, "writeback" }, \ > {1UL << PG_head, "head" }, \ > - {1UL << PG_swapcache, "swapcache" }, \ > {1UL << PG_mappedtodisk, "mappedtodisk" }, \ > {1UL << PG_reclaim, "reclaim" }, \ > {1UL << PG_swapbacked, "swapbacked" }, \ > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > index 19e796d36a62..f283c7e0a2a3 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -764,12 +764,11 @@ static int me_huge_page(struct page *p, unsigned long > pfn) > */ > > #define dirty (1UL << PG_dirty) > -#define sc (1UL << PG_swapcache) > +#define sc ((1UL << PG_swapcache) | (1UL << PG_swapbacked)) > #define unevict (1UL << PG_unevictable) > #define mlock (1UL << PG_mlocked) > #define writeback (1UL << PG_writeback) > #define lru (1UL << PG_lru) > -#define swapbacked (1UL << PG_swapbacked) > #define head (1UL << PG_head) > #define slab (1UL << PG_slab) > #define reserved (1UL << PG_reserved) > @@ -819,7 +818,6 @@ static struct page_state { > #undef mlock > #undef writeback > #undef lru > -#undef swapbacked > #undef head > #undef slab > #undef reserved > diff --git a/mm/migrate.c b/mm/migrate.c > index 0ed24b1fa77b..87f4d0f81819 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -466,13 +466,15 @@ int migrate_page_move_mapping(struct address_space > *mapping, > */ > newpage->index = page->index; > newpage->mapping = page->mapping; > - if (PageSwapBacked(page)) > - __SetPageSwapBacked(newpage); > - > get_page(newpage); /* add cache reference */ > - if (PageSwapCache(page)) { > - SetPageSwapCache(newpage); > - set_page_private(newpage, page_private(page)); > + if (PageSwapBacked(page)) { > + __SetPageSwapBacked(newpage); > + if (PageSwapCache(page)) { > + SetPageSwapCache(newpage); > + set_page_private(newpage, page_private(page)); > + } > + } else { > + VM_BUG_ON_PAGE(PageSwapCache(page), page); > } > > /* Move dirty while page refs frozen and newpage not yet exposed */ > -- > 2.11.0
