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Commit fd87526f authored by Liu Bo's avatar Liu Bo Committed by David Sterba
Browse files

Btrfs: extent map selftest: buffered write vs dio read 



This test case simulates the racy situation of buffered write vs dio
read, and see if btrfs_get_extent() would return -EEXIST.

Signed-off-by: default avatarLiu Bo <bo.li.liu@oracle.com>
Reviewed-by: default avatarJosef Bacik <jbacik@fb.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 72b28077

fs/btrfs/tests/extent-map-tests.c

+74 −0
Original line number Diff line number Diff line
@@ -182,6 +182,79 @@ static void test_case_2(struct extent_map_tree *em_tree) 
	free_extent_map_tree(em_tree);

}



static void __test_case_3(struct extent_map_tree *em_tree, u64 start)

{

	struct extent_map *em;

	u64 len = SZ_4K;

	int ret;



	em = alloc_extent_map();

	if (!em)

		/* Skip this test on error. */

		return;



	/* Add [4K, 8K) */

	em->start = SZ_4K;

	em->len = SZ_4K;

	em->block_start = SZ_4K;

	em->block_len = SZ_4K;

	ret = add_extent_mapping(em_tree, em, 0);

	ASSERT(ret == 0);

	free_extent_map(em);



	em = alloc_extent_map();

	if (!em)

		goto out;



	/* Add [0, 16K) */

	em->start = 0;

	em->len = SZ_16K;

	em->block_start = 0;

	em->block_len = SZ_16K;

	ret = btrfs_add_extent_mapping(em_tree, &em, start, len);

	if (ret)

		test_msg("case3 [0x%llx 0x%llx): ret %d\n",

			 start, start + len, ret);

	/*

	 * Since bytes within em are contiguous, em->block_start is identical to

	 * em->start.

	 */

	if (em &&

	    (start < em->start || start + len > extent_map_end(em) ||

	     em->start != em->block_start || em->len != em->block_len))

		test_msg(

"case3 [0x%llx 0x%llx): ret %d em (start 0x%llx len 0x%llx block_start 0x%llx block_len 0x%llx)\n",

			 start, start + len, ret, em->start, em->len,

			 em->block_start, em->block_len);

	free_extent_map(em);

out:

	/* free memory */

	free_extent_map_tree(em_tree);

}



/*

 * Test scenario:

 *

 * Suppose that no extent map has been loaded into memory yet.

 * There is a file extent [0, 16K), two jobs are running concurrently

 * against it, t1 is buffered writing to [4K, 8K) and t2 is doing dio

 * read from [0, 4K) or [8K, 12K) or [12K, 16K).

 *

 * t1 goes ahead of t2 and adds em [4K, 8K) into tree.

 *

 *         t1                       t2

 *  cow_file_range()	     btrfs_get_extent()

 *                            -> lookup_extent_mapping()

 *   -> add_extent_mapping()

 *                            -> add_extent_mapping()

 */

static void test_case_3(struct extent_map_tree *em_tree)

{

	__test_case_3(em_tree, 0);

	__test_case_3(em_tree, SZ_8K);

	__test_case_3(em_tree, (12 * 1024ULL));

}



int btrfs_test_extent_map()

{

	struct extent_map_tree *em_tree;
@@ -197,6 +270,7 @@ int btrfs_test_extent_map() 


	test_case_1(em_tree);

	test_case_2(em_tree);

	test_case_3(em_tree);



	kfree(em_tree);

	return 0;