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[PATCH] mm: migration page refcounting fix

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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 <npiggin@suse.de>
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Nick Piggin
2006-01-18 17:42:27 -08:00
committed by Linus Torvalds
parent e236a166b2
commit 053837fce7
7 changed files with 76 additions and 75 deletions
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29
mm/mempolicy.c
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@@ -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);
}
}