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[PATCH] page migration: fail if page is in a vma flagged VM_LOCKED
page migration currently simply retries a couple of times if try_to_unmap() fails without inspecting the return code. However, SWAP_FAIL indicates that the page is in a vma that has the VM_LOCKED flag set (if ignore_refs ==1). We can check for that return code and avoid retrying the migration. migrate_page_remove_references() now needs to return a reason why the failure occured. So switch migrate_page_remove_references to use -Exx style error messages. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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@ -3060,6 +3060,7 @@ int buffer_migrate_page(struct page *newpage, struct page *page)
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{
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struct address_space *mapping = page->mapping;
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struct buffer_head *bh, *head;
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int rc;
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if (!mapping)
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return -EAGAIN;
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@ -3069,8 +3070,9 @@ int buffer_migrate_page(struct page *newpage, struct page *page)
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head = page_buffers(page);
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if (migrate_page_remove_references(newpage, page, 3))
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return -EAGAIN;
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rc = migrate_page_remove_references(newpage, page, 3);
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if (rc)
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return rc;
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bh = head;
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do {
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18
mm/vmscan.c
18
mm/vmscan.c
@ -700,7 +700,7 @@ int migrate_page_remove_references(struct page *newpage,
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* the page.
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*/
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if (!mapping || page_mapcount(page) + nr_refs != page_count(page))
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return 1;
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return -EAGAIN;
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/*
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* Establish swap ptes for anonymous pages or destroy pte
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@ -721,13 +721,15 @@ int migrate_page_remove_references(struct page *newpage,
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* If the page was not migrated then the PageSwapCache bit
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* is still set and the operation may continue.
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*/
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try_to_unmap(page, 1);
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if (try_to_unmap(page, 1) == SWAP_FAIL)
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/* A vma has VM_LOCKED set -> Permanent failure */
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return -EPERM;
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/*
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* Give up if we were unable to remove all mappings.
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*/
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if (page_mapcount(page))
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return 1;
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return -EAGAIN;
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write_lock_irq(&mapping->tree_lock);
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@ -738,7 +740,7 @@ int migrate_page_remove_references(struct page *newpage,
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if (!page_mapping(page) || page_count(page) != nr_refs ||
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*radix_pointer != page) {
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write_unlock_irq(&mapping->tree_lock);
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return 1;
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return -EAGAIN;
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}
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/*
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@ -813,10 +815,14 @@ EXPORT_SYMBOL(migrate_page_copy);
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*/
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int migrate_page(struct page *newpage, struct page *page)
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{
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int rc;
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BUG_ON(PageWriteback(page)); /* Writeback must be complete */
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if (migrate_page_remove_references(newpage, page, 2))
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return -EAGAIN;
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rc = migrate_page_remove_references(newpage, page, 2);
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if (rc)
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return rc;
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migrate_page_copy(newpage, page);
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