From 053837fce7aa79025ed57656855df09f80175527 Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Wed, 18 Jan 2006 17:42:27 -0800 Subject: [PATCH] mm: migration page refcounting fix Migration code currently does not take a reference to target page properly, so between unlocking the pte and trying to take a new reference to the page with isolate_lru_page, anything could happen to it. Fix this by holding the pte lock until we get a chance to elevate the refcount. Other small cleanups while we're here. Signed-off-by: Nick Piggin Signed-off-by: Christoph Lameter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mempolicy.c | 29 +++++++++++++++++------------ 1 file changed, 17 insertions(+), 12 deletions(-) (limited to 'mm/mempolicy.c') diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 3171f884d245..551cde40520b 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -208,6 +208,17 @@ static int check_pte_range(struct vm_area_struct *vma, pmd_t *pmd, page = vm_normal_page(vma, addr, *pte); if (!page) continue; + /* + * The check for PageReserved here is important to avoid + * handling zero pages and other pages that may have been + * marked special by the system. + * + * If the PageReserved would not be checked here then f.e. + * the location of the zero page could have an influence + * on MPOL_MF_STRICT, zero pages would be counted for + * the per node stats, and there would be useless attempts + * to put zero pages on the migration list. + */ if (PageReserved(page)) continue; nid = page_to_nid(page); @@ -216,11 +227,8 @@ static int check_pte_range(struct vm_area_struct *vma, pmd_t *pmd, if (flags & MPOL_MF_STATS) gather_stats(page, private); - else if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) { - spin_unlock(ptl); + else if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) migrate_page_add(vma, page, private, flags); - spin_lock(ptl); - } else break; } while (pte++, addr += PAGE_SIZE, addr != end); @@ -309,6 +317,10 @@ check_range(struct mm_struct *mm, unsigned long start, unsigned long end, int err; struct vm_area_struct *first, *vma, *prev; + /* Clear the LRU lists so pages can be isolated */ + if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) + lru_add_drain_all(); + first = find_vma(mm, start); if (!first) return ERR_PTR(-EFAULT); @@ -555,15 +567,8 @@ static void migrate_page_add(struct vm_area_struct *vma, if ((flags & MPOL_MF_MOVE_ALL) || !page->mapping || PageAnon(page) || mapping_writably_mapped(page->mapping) || single_mm_mapping(vma->vm_mm, page->mapping)) { - int rc = isolate_lru_page(page); - - if (rc == 1) + if (isolate_lru_page(page)) list_add(&page->lru, pagelist); - /* - * If the isolate attempt was not successful then we just - * encountered an unswappable page. Something must be wrong. - */ - WARN_ON(rc == 0); } } -- cgit v1.2.3-59-g8ed1b