[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-devel] [PATCH 17/21] userfaultfd: remap_pages: swp_entry_swapcount
From: |
Andrea Arcangeli |
Subject: |
[Qemu-devel] [PATCH 17/21] userfaultfd: remap_pages: swp_entry_swapcount() preparation |
Date: |
Thu, 5 Mar 2015 18:18:00 +0100 |
Provide a new swapfile method for remap_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 <address@hidden>
---
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 4759491..9adda11 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -436,6 +436,7 @@ 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 *);
@@ -527,6 +528,11 @@ 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 63f55cc..04c7621 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
- [Qemu-devel] [PATCH 00/21] RFC: userfaultfd v3, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 02/21] userfaultfd: linux/Documentation/vm/userfaultfd.txt, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 06/21] userfaultfd: add VM_UFFD_MISSING and VM_UFFD_WP, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 16/21] userfaultfd: remap_pages: rmap preparation, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 17/21] userfaultfd: remap_pages: swp_entry_swapcount() preparation,
Andrea Arcangeli <=
- [Qemu-devel] [PATCH 12/21] userfaultfd: activate syscall, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 11/21] userfaultfd: buildsystem activation, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 08/21] userfaultfd: teach vma_merge to merge across vma->vm_userfaultfd_ctx, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 01/21] userfaultfd: waitqueue: add nr wake parameter to __wake_up_locked_key, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 13/21] userfaultfd: UFFDIO_COPY|UFFDIO_ZEROPAGE uAPI, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 15/21] userfaultfd: UFFDIO_COPY and UFFDIO_ZEROPAGE, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 20/21] userfaultfd: UFFDIO_REMAP, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 07/21] userfaultfd: call handle_userfault() for userfaultfd_missing() faults, Andrea Arcangeli, 2015/03/05
- [Qemu-devel] [PATCH 10/21] userfaultfd: add new syscall to provide memory externalization, Andrea Arcangeli, 2015/03/05