Commit 053837fc authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds

[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: default avatarNick Piggin <npiggin@suse.de>
Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent e236a166
......@@ -39,24 +39,3 @@ del_page_from_lru(struct zone *zone, struct page *page)
}
}
/*
* Isolate one page from the LRU lists.
*
* - zone->lru_lock must be held
*/
static inline int __isolate_lru_page(struct page *page)
{
if (unlikely(!TestClearPageLRU(page)))
return 0;
if (get_page_testone(page)) {
/*
* It is being freed elsewhere
*/
__put_page(page);
SetPageLRU(page);
return -ENOENT;
}
return 1;
}
......@@ -167,6 +167,7 @@ extern void FASTCALL(lru_cache_add_active(struct page *));
extern void FASTCALL(activate_page(struct page *));
extern void FASTCALL(mark_page_accessed(struct page *));
extern void lru_add_drain(void);
extern int lru_add_drain_all(void);
extern int rotate_reclaimable_page(struct page *page);
extern void swap_setup(void);
......
......@@ -94,6 +94,7 @@ generic_file_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
* ->private_lock (try_to_unmap_one)
* ->tree_lock (try_to_unmap_one)
* ->zone.lru_lock (follow_page->mark_page_accessed)
* ->zone.lru_lock (check_pte_range->isolate_lru_page)
* ->private_lock (page_remove_rmap->set_page_dirty)
* ->tree_lock (page_remove_rmap->set_page_dirty)
* ->inode_lock (page_remove_rmap->set_page_dirty)
......
......@@ -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);
}
}
......
......@@ -33,7 +33,7 @@
* mapping->i_mmap_lock
* anon_vma->lock
* mm->page_table_lock or pte_lock
* zone->lru_lock (in mark_page_accessed)
* zone->lru_lock (in mark_page_accessed, isolate_lru_page)
* swap_lock (in swap_duplicate, swap_info_get)
* mmlist_lock (in mmput, drain_mmlist and others)
* mapping->private_lock (in __set_page_dirty_buffers)
......
......@@ -174,6 +174,32 @@ void lru_add_drain(void)
put_cpu();
}
#ifdef CONFIG_NUMA
static void lru_add_drain_per_cpu(void *dummy)
{
lru_add_drain();
}
/*
* Returns 0 for success
*/
int lru_add_drain_all(void)
{
return schedule_on_each_cpu(lru_add_drain_per_cpu, NULL);
}
#else
/*
* Returns 0 for success
*/
int lru_add_drain_all(void)
{
lru_add_drain();
return 0;
}
#endif
/*
* This path almost never happens for VM activity - pages are normally
* freed via pagevecs. But it gets used by networking.
......
......@@ -586,7 +586,7 @@ static inline void move_to_lru(struct page *page)
}
/*
* Add isolated pages on the list back to the LRU
* Add isolated pages on the list back to the LRU.
*
* returns the number of pages put back.
*/
......@@ -760,46 +760,33 @@ int migrate_pages(struct list_head *from, struct list_head *to,
return nr_failed + retry;
}
static void lru_add_drain_per_cpu(void *dummy)
{
lru_add_drain();
}
/*
* Isolate one page from the LRU lists and put it on the
* indicated list. Do necessary cache draining if the
* page is not on the LRU lists yet.
* indicated list with elevated refcount.
*
* Result:
* 0 = page not on LRU list
* 1 = page removed from LRU list and added to the specified list.
* -ENOENT = page is being freed elsewhere.
*/
int isolate_lru_page(struct page *page)
{
int rc = 0;
struct zone *zone = page_zone(page);
int ret = 0;
redo:
spin_lock_irq(&zone->lru_lock);
rc = __isolate_lru_page(page);
if (rc == 1) {
if (PageActive(page))
del_page_from_active_list(zone, page);
else
del_page_from_inactive_list(zone, page);
}
spin_unlock_irq(&zone->lru_lock);
if (rc == 0) {
/*
* Maybe this page is still waiting for a cpu to drain it
* from one of the lru lists?
*/
rc = schedule_on_each_cpu(lru_add_drain_per_cpu, NULL);
if (rc == 0 && PageLRU(page))
goto redo;
if (PageLRU(page)) {
struct zone *zone = page_zone(page);
spin_lock_irq(&zone->lru_lock);
if (TestClearPageLRU(page)) {
ret = 1;
get_page(page);
if (PageActive(page))
del_page_from_active_list(zone, page);
else
del_page_from_inactive_list(zone, page);
}
spin_unlock_irq(&zone->lru_lock);
}
return rc;
return ret;
}
#endif
......@@ -831,18 +818,20 @@ static int isolate_lru_pages(int nr_to_scan, struct list_head *src,
page = lru_to_page(src);
prefetchw_prev_lru_page(page, src, flags);
switch (__isolate_lru_page(page)) {
case 1:
/* Succeeded to isolate page */
list_move(&page->lru, dst);
nr_taken++;
break;
case -ENOENT:
/* Not possible to isolate */
list_move(&page->lru, src);
break;
default:
if (!TestClearPageLRU(page))
BUG();
list_del(&page->lru);
if (get_page_testone(page)) {
/*
* It is being freed elsewhere
*/
__put_page(page);
SetPageLRU(page);
list_add(&page->lru, src);
continue;
} else {
list_add(&page->lru, dst);
nr_taken++;
}
}
......
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