124 lines
3.9 KiB
C
124 lines
3.9 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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* Regression2
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* Description:
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* Toshiyuki Okajima describes the following radix-tree bug:
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*
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* In the following case, we can get a hangup on
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* radix_radix_tree_gang_lookup_tag_slot.
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*
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* 0. The radix tree contains RADIX_TREE_MAP_SIZE items. And the tag of
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* a certain item has PAGECACHE_TAG_DIRTY.
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* 1. radix_tree_range_tag_if_tagged(, start, end, , PAGECACHE_TAG_DIRTY,
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* PAGECACHE_TAG_TOWRITE) is called to add PAGECACHE_TAG_TOWRITE tag
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* for the tag which has PAGECACHE_TAG_DIRTY. However, there is no tag with
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* PAGECACHE_TAG_DIRTY within the range from start to end. As the result,
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* There is no tag with PAGECACHE_TAG_TOWRITE but the root tag has
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* PAGECACHE_TAG_TOWRITE.
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* 2. An item is added into the radix tree and then the level of it is
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* extended into 2 from 1. At that time, the new radix tree node succeeds
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* the tag status of the root tag. Therefore the tag of the new radix tree
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* node has PAGECACHE_TAG_TOWRITE but there is not slot with
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* PAGECACHE_TAG_TOWRITE tag in the child node of the new radix tree node.
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* 3. The tag of a certain item is cleared with PAGECACHE_TAG_DIRTY.
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* 4. All items within the index range from 0 to RADIX_TREE_MAP_SIZE - 1 are
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* released. (Only the item which index is RADIX_TREE_MAP_SIZE exist in the
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* radix tree.) As the result, the slot of the radix tree node is NULL but
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* the tag which corresponds to the slot has PAGECACHE_TAG_TOWRITE.
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* 5. radix_tree_gang_lookup_tag_slot(PAGECACHE_TAG_TOWRITE) calls
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* __lookup_tag. __lookup_tag returns with 0. And __lookup_tag doesn't
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* change the index that is the input and output parameter. Because the 1st
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* slot of the radix tree node is NULL, but the tag which corresponds to
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* the slot has PAGECACHE_TAG_TOWRITE.
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* Therefore radix_tree_gang_lookup_tag_slot tries to get some items by
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* calling __lookup_tag, but it cannot get any items forever.
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*
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* The fix is to change that radix_tree_tag_if_tagged doesn't tag the root tag
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* if it doesn't set any tags within the specified range.
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*
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* Running:
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* This test should run to completion immediately. The above bug would cause it
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* to hang indefinitely.
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*
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* Upstream commit:
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* Not yet
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*/
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#include <linux/kernel.h>
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#include <linux/gfp.h>
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#include <linux/slab.h>
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#include <linux/radix-tree.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include "regression.h"
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#include "test.h"
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#define PAGECACHE_TAG_DIRTY XA_MARK_0
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#define PAGECACHE_TAG_WRITEBACK XA_MARK_1
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#define PAGECACHE_TAG_TOWRITE XA_MARK_2
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static RADIX_TREE(mt_tree, GFP_KERNEL);
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unsigned long page_count = 0;
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struct page {
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unsigned long index;
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};
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static struct page *page_alloc(void)
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{
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struct page *p;
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p = malloc(sizeof(struct page));
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p->index = page_count++;
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return p;
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}
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void regression2_test(void)
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{
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int i;
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struct page *p;
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int max_slots = RADIX_TREE_MAP_SIZE;
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unsigned long int start, end;
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struct page *pages[1];
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printv(1, "running regression test 2 (should take milliseconds)\n");
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/* 0. */
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for (i = 0; i <= max_slots - 1; i++) {
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p = page_alloc();
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radix_tree_insert(&mt_tree, i, p);
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}
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radix_tree_tag_set(&mt_tree, max_slots - 1, PAGECACHE_TAG_DIRTY);
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/* 1. */
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start = 0;
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end = max_slots - 2;
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tag_tagged_items(&mt_tree, start, end, 1,
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PAGECACHE_TAG_DIRTY, PAGECACHE_TAG_TOWRITE);
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/* 2. */
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p = page_alloc();
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radix_tree_insert(&mt_tree, max_slots, p);
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/* 3. */
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radix_tree_tag_clear(&mt_tree, max_slots - 1, PAGECACHE_TAG_DIRTY);
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/* 4. */
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for (i = max_slots - 1; i >= 0; i--)
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free(radix_tree_delete(&mt_tree, i));
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/* 5. */
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// NOTE: start should not be 0 because radix_tree_gang_lookup_tag_slot
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// can return.
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start = 1;
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end = max_slots - 2;
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radix_tree_gang_lookup_tag_slot(&mt_tree, (void ***)pages, start, end,
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PAGECACHE_TAG_TOWRITE);
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/* We remove all the remained nodes */
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free(radix_tree_delete(&mt_tree, max_slots));
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BUG_ON(!radix_tree_empty(&mt_tree));
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printv(1, "regression test 2, done\n");
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}
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