diff options
| -rw-r--r-- | mm/memory.c | 10 | ||||
| -rw-r--r-- | mm/rmap.c | 21 | ||||
| -rw-r--r-- | mm/swapfile.c | 55 |
3 files changed, 21 insertions, 65 deletions
diff --git a/mm/memory.c b/mm/memory.c index 1c0a3db..da91b7b 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1686,10 +1686,6 @@ static int do_swap_page(struct mm_struct * mm, } /* The page isn't present yet, go ahead with the fault. */ - - swap_free(entry); - if (vm_swap_full()) - remove_exclusive_swap_page(page); inc_mm_counter(mm, rss); pte = mk_pte(page, vma->vm_page_prot); @@ -1697,12 +1693,16 @@ static int do_swap_page(struct mm_struct * mm, pte = maybe_mkwrite(pte_mkdirty(pte), vma); write_access = 0; } - unlock_page(page); flush_icache_page(vma, page); set_pte_at(mm, address, page_table, pte); page_add_anon_rmap(page, vma, address); + swap_free(entry); + if (vm_swap_full()) + remove_exclusive_swap_page(page); + unlock_page(page); + if (write_access) { if (do_wp_page(mm, vma, address, page_table, pmd, pte) == VM_FAULT_OOM) @@ -539,27 +539,6 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma) goto out_unmap; } - /* - * Don't pull an anonymous page out from under get_user_pages. - * GUP carefully breaks COW and raises page count (while holding - * page_table_lock, as we have here) to make sure that the page - * cannot be freed. If we unmap that page here, a user write - * access to the virtual address will bring back the page, but - * its raised count will (ironically) be taken to mean it's not - * an exclusive swap page, do_wp_page will replace it by a copy - * page, and the user never get to see the data GUP was holding - * the original page for. - * - * This test is also useful for when swapoff (unuse_process) has - * to drop page lock: its reference to the page stops existing - * ptes from being unmapped, so swapoff can make progress. - */ - if (PageSwapCache(page) && - page_count(page) != page_mapcount(page) + 2) { - ret = SWAP_FAIL; - goto out_unmap; - } - /* Nuke the page table entry. */ flush_cache_page(vma, address, page_to_pfn(page)); pteval = ptep_clear_flush(vma, address, pte); diff --git a/mm/swapfile.c b/mm/swapfile.c index da48405..60cd24a 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -276,61 +276,37 @@ void swap_free(swp_entry_t entry) } /* - * Check if we're the only user of a swap page, - * when the page is locked. + * How many references to page are currently swapped out? */ -static int exclusive_swap_page(struct page *page) +static inline int page_swapcount(struct page *page) { - int retval = 0; - struct swap_info_struct * p; + int count = 0; + struct swap_info_struct *p; swp_entry_t entry; entry.val = page->private; p = swap_info_get(entry); if (p) { - /* Is the only swap cache user the cache itself? */ - if (p->swap_map[swp_offset(entry)] == 1) { - /* Recheck the page count with the swapcache lock held.. */ - write_lock_irq(&swapper_space.tree_lock); - if (page_count(page) == 2) - retval = 1; - write_unlock_irq(&swapper_space.tree_lock); - } + /* Subtract the 1 for the swap cache itself */ + count = p->swap_map[swp_offset(entry)] - 1; swap_info_put(p); } - return retval; + return count; } /* * We can use this swap cache entry directly * if there are no other references to it. - * - * Here "exclusive_swap_page()" does the real - * work, but we opportunistically check whether - * we need to get all the locks first.. */ int can_share_swap_page(struct page *page) { - int retval = 0; + int count; - if (!PageLocked(page)) - BUG(); - switch (page_count(page)) { - case 3: - if (!PagePrivate(page)) - break; - /* Fallthrough */ - case 2: - if (!PageSwapCache(page)) - break; - retval = exclusive_swap_page(page); - break; - case 1: - if (PageReserved(page)) - break; - retval = 1; - } - return retval; + BUG_ON(!PageLocked(page)); + count = page_mapcount(page); + if (count <= 1 && PageSwapCache(page)) + count += page_swapcount(page); + return count == 1; } /* @@ -529,9 +505,10 @@ static int unuse_mm(struct mm_struct *mm, if (!down_read_trylock(&mm->mmap_sem)) { /* - * Our reference to the page stops try_to_unmap_one from - * unmapping its ptes, so swapoff can make progress. + * Activate page so shrink_cache is unlikely to unmap its + * ptes while lock is dropped, so swapoff can make progress. */ + activate_page(page); unlock_page(page); down_read(&mm->mmap_sem); lock_page(page); |
