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: Liu Bo <bo.li....@oracle.com>
---
fs/btrfs/tests/extent-map-tests.c | 73 +++++++++++++++++++++++++++++++++++++++
1 file changed, 73 insertions(+)
diff --git a/fs/btrfs/tests/extent-map-tests.c
b/fs/btrfs/tests/extent-map-tests.c
index 0407396..2adf55f 100644
--- a/fs/btrfs/tests/extent-map-tests.c
+++ b/fs/btrfs/tests/extent-map-tests.c
@@ -181,6 +181,78 @@ 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;
@@ -196,6 +268,7 @@ 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;
--
2.9.4
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