memory-failure.c

	/*
	 * Torn down by someone else?
	 */
	if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
		action_result(pfn, "already truncated LRU", IGNORED);
		res = -EBUSY;
		goto out;
	}

	res = -EBUSY;
	for (ps = error_states;; ps++) {
		if ((p->flags & ps->mask) == ps->res) {
			res = page_action(ps, p, pfn);
			break;
		}
	}
out:
	unlock_page(p);
	return res;
}
EXPORT_SYMBOL_GPL(__memory_failure);

/**
 * memory_failure - Handle memory failure of a page.
 * @pfn: Page Number of the corrupted page
 * @trapno: Trap number reported in the signal to user space.
 *
 * This function is called by the low level machine check code
 * of an architecture when it detects hardware memory corruption
 * of a page. It tries its best to recover, which includes
 * dropping pages, killing processes etc.
 *
 * The function is primarily of use for corruptions that
 * happen outside the current execution context (e.g. when
 * detected by a background scrubber)
 *
 * Must run in process context (e.g. a work queue) with interrupts
 * enabled and no spinlocks hold.
 */
void memory_failure(unsigned long pfn, int trapno)
{
	__memory_failure(pfn, trapno, 0);
}

/**
 * unpoison_memory - Unpoison a previously poisoned page
 * @pfn: Page number of the to be unpoisoned page
 *
 * Software-unpoison a page that has been poisoned by
 * memory_failure() earlier.
 *
 * This is only done on the software-level, so it only works
 * for linux injected failures, not real hardware failures
 *
 * Returns 0 for success, otherwise -errno.
 */
int unpoison_memory(unsigned long pfn)
{
	struct page *page;
	struct page *p;
	int freeit = 0;

	if (!pfn_valid(pfn))
		return -ENXIO;

	p = pfn_to_page(pfn);
	page = compound_head(p);

	if (!PageHWPoison(p)) {
		pr_debug("MCE: Page was already unpoisoned %#lx\n", pfn);
		return 0;
	}

	if (!get_page_unless_zero(page)) {
		if (TestClearPageHWPoison(p))
			atomic_long_dec(&mce_bad_pages);
		pr_debug("MCE: Software-unpoisoned free page %#lx\n", pfn);
		return 0;
	}

	lock_page_nosync(page);
	/*
	 * This test is racy because PG_hwpoison is set outside of page lock.
	 * That's acceptable because that won't trigger kernel panic. Instead,
	 * the PG_hwpoison page will be caught and isolated on the entrance to
	 * the free buddy page pool.
	 */
	if (TestClearPageHWPoison(p)) {
		pr_debug("MCE: Software-unpoisoned page %#lx\n", pfn);
		atomic_long_dec(&mce_bad_pages);
		freeit = 1;
	}
	unlock_page(page);

	put_page(page);
	if (freeit)
		put_page(page);

	return 0;
}
EXPORT_SYMBOL(unpoison_memory);