From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrea Arcangeli Subject: [PATCH 11/17] mm: swp_entry_swapcount Date: Fri, 3 Oct 2014 19:08:01 +0200 Message-ID: <1412356087-16115-12-git-send-email-aarcange@redhat.com> References: <1412356087-16115-1-git-send-email-aarcange@redhat.com> Return-path: In-Reply-To: <1412356087-16115-1-git-send-email-aarcange-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: qemu-devel-qX2TKyscuCcdnm+yROfE0A@public.gmane.org, kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Cc: Linus Torvalds , Andres Lagar-Cavilla , Dave Hansen , Paolo Bonzini , Rik van Riel , Mel Gorman , Andy Lutomirski , Andrew Morton , Sasha Levin , Hugh Dickins , Peter Feiner , "\\\"Dr. David Alan Gilbert\\\"" , Christopher Covington , Johannes Weiner , Android Kernel Team , Robert Love , Dmitry Adamushko , Neil Brown , Mike Hommey , Taras Glek , Jan Kara , KOSAKI Motohiro , Michel Lespinasse , Minc List-Id: linux-api@vger.kernel.org Provide a new swapfile method for remap_anon_pages to verify the swap entry is mapped only in one vma before relocating the swap entry in a different virtual address. Otherwise if the swap entry is mapped in multiple vmas, when the page is swapped back in, it could get mapped in a non linear way in some anon_vma. Signed-off-by: Andrea Arcangeli --- include/linux/swap.h | 6 ++++++ mm/swapfile.c | 13 +++++++++++++ 2 files changed, 19 insertions(+) diff --git a/include/linux/swap.h b/include/linux/swap.h index 8197452..af9977c 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -458,6 +458,7 @@ extern unsigned int count_swap_pages(int, int); extern sector_t map_swap_page(struct page *, struct block_device **); extern sector_t swapdev_block(int, pgoff_t); extern int page_swapcount(struct page *); +extern int swp_entry_swapcount(swp_entry_t entry); extern struct swap_info_struct *page_swap_info(struct page *); extern int reuse_swap_page(struct page *); extern int try_to_free_swap(struct page *); @@ -559,6 +560,11 @@ static inline int page_swapcount(struct page *page) return 0; } +static inline int swp_entry_swapcount(swp_entry_t entry) +{ + return 0; +} + #define reuse_swap_page(page) (page_mapcount(page) == 1) static inline int try_to_free_swap(struct page *page) diff --git a/mm/swapfile.c b/mm/swapfile.c index 8798b2e..4cc9af6 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -874,6 +874,19 @@ int page_swapcount(struct page *page) return count; } +int swp_entry_swapcount(swp_entry_t entry) +{ + int count = 0; + struct swap_info_struct *p; + + p = swap_info_get(entry); + if (p) { + count = swap_count(p->swap_map[swp_offset(entry)]); + spin_unlock(&p->lock); + } + return count; +} + /* * We can write to an anon page without COW if there are no other references * to it. And as a side-effect, free up its swap: because the old content