From: Christoph Lameter Date: Wed, 1 Mar 2006 00:59:16 +0000 (-0800) Subject: [PATCH] remove_from_swap: fix locking X-Git-Tag: v2.6.16-rc6~146 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=e8788c0cce63e0cc8689a123d1ce0af1e28cd583;p=linux.git [PATCH] remove_from_swap: fix locking remove_from_swap() currently attempts to use page_lock_anon_vma to obtain an anon_vma lock. That is not working since the page may have been remapped via swap ptes in order to move the page. However, do_migrate_pages() obtain the mmap_sem lock and therefore there is a guarantee that the anonymous vma will not vanish from under us. There is therefore no need to use page_lock_anon_vma. Signed-off-by: Christoph Lameter Acked-by: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/rmap.c b/mm/rmap.c index df2c41c2a9a2..d8ce5ff61454 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -212,25 +212,33 @@ static struct anon_vma *page_lock_anon_vma(struct page *page) * through real pte's pointing to valid pages and then releasing * the page from the swap cache. * - * Must hold page lock on page. + * Must hold page lock on page and mmap_sem of one vma that contains + * the page. */ void remove_from_swap(struct page *page) { struct anon_vma *anon_vma; struct vm_area_struct *vma; + unsigned long mapping; - if (!PageAnon(page) || !PageSwapCache(page)) + if (!PageSwapCache(page)) return; - anon_vma = page_lock_anon_vma(page); - if (!anon_vma) + mapping = (unsigned long)page->mapping; + + if (!mapping || (mapping & PAGE_MAPPING_ANON) == 0) return; + /* + * We hold the mmap_sem lock. So no need to call page_lock_anon_vma. + */ + anon_vma = (struct anon_vma *) (mapping - PAGE_MAPPING_ANON); + spin_lock(&anon_vma->lock); + list_for_each_entry(vma, &anon_vma->head, anon_vma_node) remove_vma_swap(vma, page); spin_unlock(&anon_vma->lock); - delete_from_swap_cache(page); } EXPORT_SYMBOL(remove_from_swap);