1 files changed, 515 insertions, 1 deletions

diff --git a/fs/btrfs/tests/free-space-tests.c b/fs/btrfs/tests/free-space-tests.c
index c8d9ddf84c69..2299bfde39ee 100644
--- a/fs/btrfs/tests/free-space-tests.c
+++ b/fs/btrfs/tests/free-space-tests.c
@@ -40,11 +40,12 @@ static struct btrfs_block_group_cache *init_test_block_group(void)
 	cache->key.offset = 1024 * 1024 * 1024;
 	cache->key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
 	cache->sectorsize = 4096;
+	cache->full_stripe_len = 4096;
 
 	spin_lock_init(&cache->lock);
 	INIT_LIST_HEAD(&cache->list);
 	INIT_LIST_HEAD(&cache->cluster_list);
-	INIT_LIST_HEAD(&cache->new_bg_list);
+	INIT_LIST_HEAD(&cache->bg_list);
 
 	btrfs_init_free_space_ctl(cache);
 
@@ -364,6 +365,517 @@ static int test_bitmaps_and_extents(struct btrfs_block_group_cache *cache)
 	return 0;
 }
 
+/* Used by test_steal_space_from_bitmap_to_extent(). */
+static bool test_use_bitmap(struct btrfs_free_space_ctl *ctl,
+			    struct btrfs_free_space *info)
+{
+	return ctl->free_extents > 0;
+}
+
+/* Used by test_steal_space_from_bitmap_to_extent(). */
+static int
+check_num_extents_and_bitmaps(const struct btrfs_block_group_cache *cache,
+			      const int num_extents,
+			      const int num_bitmaps)
+{
+	if (cache->free_space_ctl->free_extents != num_extents) {
+		test_msg("Incorrect # of extent entries in the cache: %d, expected %d\n",
+			 cache->free_space_ctl->free_extents, num_extents);
+		return -EINVAL;
+	}
+	if (cache->free_space_ctl->total_bitmaps != num_bitmaps) {
+		test_msg("Incorrect # of extent entries in the cache: %d, expected %d\n",
+			 cache->free_space_ctl->total_bitmaps, num_bitmaps);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+/* Used by test_steal_space_from_bitmap_to_extent(). */
+static int check_cache_empty(struct btrfs_block_group_cache *cache)
+{
+	u64 offset;
+	u64 max_extent_size;
+
+	/*
+	 * Now lets confirm that there's absolutely no free space left to
+	 * allocate.
+	 */
+	if (cache->free_space_ctl->free_space != 0) {
+		test_msg("Cache free space is not 0\n");
+		return -EINVAL;
+	}
+
+	/* And any allocation request, no matter how small, should fail now. */
+	offset = btrfs_find_space_for_alloc(cache, 0, 4096, 0,
+					    &max_extent_size);
+	if (offset != 0) {
+		test_msg("Space allocation did not fail, returned offset: %llu",
+			 offset);
+		return -EINVAL;
+	}
+
+	/* And no extent nor bitmap entries in the cache anymore. */
+	return check_num_extents_and_bitmaps(cache, 0, 0);
+}
+
+/*
+ * Before we were able to steal free space from a bitmap entry to an extent
+ * entry, we could end up with 2 entries representing a contiguous free space.
+ * One would be an extent entry and the other a bitmap entry. Since in order
+ * to allocate space to a caller we use only 1 entry, we couldn't return that
+ * whole range to the caller if it was requested. This forced the caller to
+ * either assume ENOSPC or perform several smaller space allocations, which
+ * wasn't optimal as they could be spread all over the block group while under
+ * concurrency (extra overhead and fragmentation).
+ *
+ * This stealing approach is benefical, since we always prefer to allocate from
+ * extent entries, both for clustered and non-clustered allocation requests.
+ */
+static int
+test_steal_space_from_bitmap_to_extent(struct btrfs_block_group_cache *cache)
+{
+	int ret;
+	u64 offset;
+	u64 max_extent_size;
+
+	bool (*use_bitmap_op)(struct btrfs_free_space_ctl *,
+			      struct btrfs_free_space *);
+
+	test_msg("Running space stealing from bitmap to extent\n");
+
+	/*
+	 * For this test, we want to ensure we end up with an extent entry
+	 * immediately adjacent to a bitmap entry, where the bitmap starts
+	 * at an offset where the extent entry ends. We keep adding and
+	 * removing free space to reach into this state, but to get there
+	 * we need to reach a point where marking new free space doesn't
+	 * result in adding new extent entries or merging the new space
+	 * with existing extent entries - the space ends up being marked
+	 * in an existing bitmap that covers the new free space range.
+	 *
+	 * To get there, we need to reach the threshold defined set at
+	 * cache->free_space_ctl->extents_thresh, which currently is
+	 * 256 extents on a x86_64 system at least, and a few other
+	 * conditions (check free_space_cache.c). Instead of making the
+	 * test much longer and complicated, use a "use_bitmap" operation
+	 * that forces use of bitmaps as soon as we have at least 1
+	 * extent entry.
+	 */
+	use_bitmap_op = cache->free_space_ctl->op->use_bitmap;
+	cache->free_space_ctl->op->use_bitmap = test_use_bitmap;
+
+	/*
+	 * Extent entry covering free space range [128Mb - 256Kb, 128Mb - 128Kb[
+	 */
+	ret = test_add_free_space_entry(cache, 128 * 1024 * 1024 - 256 * 1024,
+					128 * 1024, 0);
+	if (ret) {
+		test_msg("Couldn't add extent entry %d\n", ret);
+		return ret;
+	}
+
+	/* Bitmap entry covering free space range [128Mb + 512Kb, 256Mb[ */
+	ret = test_add_free_space_entry(cache, 128 * 1024 * 1024 + 512 * 1024,
+					128 * 1024 * 1024 - 512 * 1024, 1);
+	if (ret) {
+		test_msg("Couldn't add bitmap entry %d\n", ret);
+		return ret;
+	}
+
+	ret = check_num_extents_and_bitmaps(cache, 2, 1);
+	if (ret)
+		return ret;
+
+	/*
+	 * Now make only the first 256Kb of the bitmap marked as free, so that
+	 * we end up with only the following ranges marked as free space:
+	 *
+	 * [128Mb - 256Kb, 128Mb - 128Kb[
+	 * [128Mb + 512Kb, 128Mb + 768Kb[
+	 */
+	ret = btrfs_remove_free_space(cache,
+				      128 * 1024 * 1024 + 768 * 1024,
+				      128 * 1024 * 1024 - 768 * 1024);
+	if (ret) {
+		test_msg("Failed to free part of bitmap space %d\n", ret);
+		return ret;
+	}
+
+	/* Confirm that only those 2 ranges are marked as free. */
+	if (!test_check_exists(cache, 128 * 1024 * 1024 - 256 * 1024,
+			       128 * 1024)) {
+		test_msg("Free space range missing\n");
+		return -ENOENT;
+	}
+	if (!test_check_exists(cache, 128 * 1024 * 1024 + 512 * 1024,
+			       256 * 1024)) {
+		test_msg("Free space range missing\n");
+		return -ENOENT;
+	}
+
+	/*
+	 * Confirm that the bitmap range [128Mb + 768Kb, 256Mb[ isn't marked
+	 * as free anymore.
+	 */
+	if (test_check_exists(cache, 128 * 1024 * 1024 + 768 * 1024,
+			      128 * 1024 * 1024 - 768 * 1024)) {
+		test_msg("Bitmap region not removed from space cache\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * Confirm that the region [128Mb + 256Kb, 128Mb + 512Kb[, which is
+	 * covered by the bitmap, isn't marked as free.
+	 */
+	if (test_check_exists(cache, 128 * 1024 * 1024 + 256 * 1024,
+			      256 * 1024)) {
+		test_msg("Invalid bitmap region marked as free\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * Confirm that the region [128Mb, 128Mb + 256Kb[, which is covered
+	 * by the bitmap too, isn't marked as free either.
+	 */
+	if (test_check_exists(cache, 128 * 1024 * 1024,
+			      256 * 1024)) {
+		test_msg("Invalid bitmap region marked as free\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * Now lets mark the region [128Mb, 128Mb + 512Kb[ as free too. But,
+	 * lets make sure the free space cache marks it as free in the bitmap,
+	 * and doesn't insert a new extent entry to represent this region.
+	 */
+	ret = btrfs_add_free_space(cache, 128 * 1024 * 1024, 512 * 1024);
+	if (ret) {
+		test_msg("Error adding free space: %d\n", ret);
+		return ret;
+	}
+	/* Confirm the region is marked as free. */
+	if (!test_check_exists(cache, 128 * 1024 * 1024, 512 * 1024)) {
+		test_msg("Bitmap region not marked as free\n");
+		return -ENOENT;
+	}
+
+	/*
+	 * Confirm that no new extent entries or bitmap entries were added to
+	 * the cache after adding that free space region.
+	 */
+	ret = check_num_extents_and_bitmaps(cache, 2, 1);
+	if (ret)
+		return ret;
+
+	/*
+	 * Now lets add a small free space region to the right of the previous
+	 * one, which is not contiguous with it and is part of the bitmap too.
+	 * The goal is to test that the bitmap entry space stealing doesn't
+	 * steal this space region.
+	 */
+	ret = btrfs_add_free_space(cache, 128 * 1024 * 1024 + 16 * 1024 * 1024,
+				   4096);
+	if (ret) {
+		test_msg("Error adding free space: %d\n", ret);
+		return ret;
+	}
+
+	/*
+	 * Confirm that no new extent entries or bitmap entries were added to
+	 * the cache after adding that free space region.
+	 */
+	ret = check_num_extents_and_bitmaps(cache, 2, 1);
+	if (ret)
+		return ret;
+
+	/*
+	 * Now mark the region [128Mb - 128Kb, 128Mb[ as free too. This will
+	 * expand the range covered by the existing extent entry that represents
+	 * the free space [128Mb - 256Kb, 128Mb - 128Kb[.
+	 */
+	ret = btrfs_add_free_space(cache, 128 * 1024 * 1024 - 128 * 1024,
+				   128 * 1024);
+	if (ret) {
+		test_msg("Error adding free space: %d\n", ret);
+		return ret;
+	}
+	/* Confirm the region is marked as free. */
+	if (!test_check_exists(cache, 128 * 1024 * 1024 - 128 * 1024,
+			       128 * 1024)) {
+		test_msg("Extent region not marked as free\n");
+		return -ENOENT;
+	}
+
+	/*
+	 * Confirm that our extent entry didn't stole all free space from the
+	 * bitmap, because of the small 4Kb free space region.
+	 */
+	ret = check_num_extents_and_bitmaps(cache, 2, 1);
+	if (ret)
+		return ret;
+
+	/*
+	 * So now we have the range [128Mb - 256Kb, 128Mb + 768Kb[ as free
+	 * space. Without stealing bitmap free space into extent entry space,
+	 * we would have all this free space represented by 2 entries in the
+	 * cache:
+	 *
+	 * extent entry covering range: [128Mb - 256Kb, 128Mb[
+	 * bitmap entry covering range: [128Mb, 128Mb + 768Kb[
+	 *
+	 * Attempting to allocate the whole free space (1Mb) would fail, because
+	 * we can't allocate from multiple entries.
+	 * With the bitmap free space stealing, we get a single extent entry
+	 * that represents the 1Mb free space, and therefore we're able to
+	 * allocate the whole free space at once.
+	 */
+	if (!test_check_exists(cache, 128 * 1024 * 1024 - 256 * 1024,
+			       1 * 1024 * 1024)) {
+		test_msg("Expected region not marked as free\n");
+		return -ENOENT;
+	}
+
+	if (cache->free_space_ctl->free_space != (1 * 1024 * 1024 + 4096)) {
+		test_msg("Cache free space is not 1Mb + 4Kb\n");
+		return -EINVAL;
+	}
+
+	offset = btrfs_find_space_for_alloc(cache,
+					    0, 1 * 1024 * 1024, 0,
+					    &max_extent_size);
+	if (offset != (128 * 1024 * 1024 - 256 * 1024)) {
+		test_msg("Failed to allocate 1Mb from space cache, returned offset is: %llu\n",
+			 offset);
+		return -EINVAL;
+	}
+
+	/* All that remains is a 4Kb free space region in a bitmap. Confirm. */
+	ret = check_num_extents_and_bitmaps(cache, 1, 1);
+	if (ret)
+		return ret;
+
+	if (cache->free_space_ctl->free_space != 4096) {
+		test_msg("Cache free space is not 4Kb\n");
+		return -EINVAL;
+	}
+
+	offset = btrfs_find_space_for_alloc(cache,
+					    0, 4096, 0,
+					    &max_extent_size);
+	if (offset != (128 * 1024 * 1024 + 16 * 1024 * 1024)) {
+		test_msg("Failed to allocate 4Kb from space cache, returned offset is: %llu\n",
+			 offset);
+		return -EINVAL;
+	}
+
+	ret = check_cache_empty(cache);
+	if (ret)
+		return ret;
+
+	__btrfs_remove_free_space_cache(cache->free_space_ctl);
+
+	/*
+	 * Now test a similar scenario, but where our extent entry is located
+	 * to the right of the bitmap entry, so that we can check that stealing
+	 * space from a bitmap to the front of an extent entry works.
+	 */
+
+	/*
+	 * Extent entry covering free space range [128Mb + 128Kb, 128Mb + 256Kb[
+	 */
+	ret = test_add_free_space_entry(cache, 128 * 1024 * 1024 + 128 * 1024,
+					128 * 1024, 0);
+	if (ret) {
+		test_msg("Couldn't add extent entry %d\n", ret);
+		return ret;
+	}
+
+	/* Bitmap entry covering free space range [0, 128Mb - 512Kb[ */
+	ret = test_add_free_space_entry(cache, 0,
+					128 * 1024 * 1024 - 512 * 1024, 1);
+	if (ret) {
+		test_msg("Couldn't add bitmap entry %d\n", ret);
+		return ret;
+	}
+
+	ret = check_num_extents_and_bitmaps(cache, 2, 1);
+	if (ret)
+		return ret;
+
+	/*
+	 * Now make only the last 256Kb of the bitmap marked as free, so that
+	 * we end up with only the following ranges marked as free space:
+	 *
+	 * [128Mb + 128b, 128Mb + 256Kb[
+	 * [128Mb - 768Kb, 128Mb - 512Kb[
+	 */
+	ret = btrfs_remove_free_space(cache,
+				      0,
+				      128 * 1024 * 1024 - 768 * 1024);
+	if (ret) {
+		test_msg("Failed to free part of bitmap space %d\n", ret);
+		return ret;
+	}
+
+	/* Confirm that only those 2 ranges are marked as free. */
+	if (!test_check_exists(cache, 128 * 1024 * 1024 + 128 * 1024,
+			       128 * 1024)) {
+		test_msg("Free space range missing\n");
+		return -ENOENT;
+	}
+	if (!test_check_exists(cache, 128 * 1024 * 1024 - 768 * 1024,
+			       256 * 1024)) {
+		test_msg("Free space range missing\n");
+		return -ENOENT;
+	}
+
+	/*
+	 * Confirm that the bitmap range [0, 128Mb - 768Kb[ isn't marked
+	 * as free anymore.
+	 */
+	if (test_check_exists(cache, 0,
+			      128 * 1024 * 1024 - 768 * 1024)) {
+		test_msg("Bitmap region not removed from space cache\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * Confirm that the region [128Mb - 512Kb, 128Mb[, which is
+	 * covered by the bitmap, isn't marked as free.
+	 */
+	if (test_check_exists(cache, 128 * 1024 * 1024 - 512 * 1024,
+			      512 * 1024)) {
+		test_msg("Invalid bitmap region marked as free\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * Now lets mark the region [128Mb - 512Kb, 128Mb[ as free too. But,
+	 * lets make sure the free space cache marks it as free in the bitmap,
+	 * and doesn't insert a new extent entry to represent this region.
+	 */
+	ret = btrfs_add_free_space(cache, 128 * 1024 * 1024 - 512 * 1024,
+				   512 * 1024);
+	if (ret) {
+		test_msg("Error adding free space: %d\n", ret);
+		return ret;
+	}
+	/* Confirm the region is marked as free. */
+	if (!test_check_exists(cache, 128 * 1024 * 1024 - 512 * 1024,
+			       512 * 1024)) {
+		test_msg("Bitmap region not marked as free\n");
+		return -ENOENT;
+	}
+
+	/*
+	 * Confirm that no new extent entries or bitmap entries were added to
+	 * the cache after adding that free space region.
+	 */
+	ret = check_num_extents_and_bitmaps(cache, 2, 1);
+	if (ret)
+		return ret;
+
+	/*
+	 * Now lets add a small free space region to the left of the previous
+	 * one, which is not contiguous with it and is part of the bitmap too.
+	 * The goal is to test that the bitmap entry space stealing doesn't
+	 * steal this space region.
+	 */
+	ret = btrfs_add_free_space(cache, 32 * 1024 * 1024, 8192);
+	if (ret) {
+		test_msg("Error adding free space: %d\n", ret);
+		return ret;
+	}
+
+	/*
+	 * Now mark the region [128Mb, 128Mb + 128Kb[ as free too. This will
+	 * expand the range covered by the existing extent entry that represents
+	 * the free space [128Mb + 128Kb, 128Mb + 256Kb[.
+	 */
+	ret = btrfs_add_free_space(cache, 128 * 1024 * 1024, 128 * 1024);
+	if (ret) {
+		test_msg("Error adding free space: %d\n", ret);
+		return ret;
+	}
+	/* Confirm the region is marked as free. */
+	if (!test_check_exists(cache, 128 * 1024 * 1024, 128 * 1024)) {
+		test_msg("Extent region not marked as free\n");
+		return -ENOENT;
+	}
+
+	/*
+	 * Confirm that our extent entry didn't stole all free space from the
+	 * bitmap, because of the small 8Kb free space region.
+	 */
+	ret = check_num_extents_and_bitmaps(cache, 2, 1);
+	if (ret)
+		return ret;
+
+	/*
+	 * So now we have the range [128Mb - 768Kb, 128Mb + 256Kb[ as free
+	 * space. Without stealing bitmap free space into extent entry space,
+	 * we would have all this free space represented by 2 entries in the
+	 * cache:
+	 *
+	 * extent entry covering range: [128Mb, 128Mb + 256Kb[
+	 * bitmap entry covering range: [128Mb - 768Kb, 128Mb[
+	 *
+	 * Attempting to allocate the whole free space (1Mb) would fail, because
+	 * we can't allocate from multiple entries.
+	 * With the bitmap free space stealing, we get a single extent entry
+	 * that represents the 1Mb free space, and therefore we're able to
+	 * allocate the whole free space at once.
+	 */
+	if (!test_check_exists(cache, 128 * 1024 * 1024 - 768 * 1024,
+			       1 * 1024 * 1024)) {
+		test_msg("Expected region not marked as free\n");
+		return -ENOENT;
+	}
+
+	if (cache->free_space_ctl->free_space != (1 * 1024 * 1024 + 8192)) {
+		test_msg("Cache free space is not 1Mb + 8Kb\n");
+		return -EINVAL;
+	}
+
+	offset = btrfs_find_space_for_alloc(cache,
+					    0, 1 * 1024 * 1024, 0,
+					    &max_extent_size);
+	if (offset != (128 * 1024 * 1024 - 768 * 1024)) {
+		test_msg("Failed to allocate 1Mb from space cache, returned offset is: %llu\n",
+			 offset);
+		return -EINVAL;
+	}
+
+	/* All that remains is a 8Kb free space region in a bitmap. Confirm. */
+	ret = check_num_extents_and_bitmaps(cache, 1, 1);
+	if (ret)
+		return ret;
+
+	if (cache->free_space_ctl->free_space != 8192) {
+		test_msg("Cache free space is not 8Kb\n");
+		return -EINVAL;
+	}
+
+	offset = btrfs_find_space_for_alloc(cache,
+					    0, 8192, 0,
+					    &max_extent_size);
+	if (offset != (32 * 1024 * 1024)) {
+		test_msg("Failed to allocate 8Kb from space cache, returned offset is: %llu\n",
+			 offset);
+		return -EINVAL;
+	}
+
+	ret = check_cache_empty(cache);
+	if (ret)
+		return ret;
+
+	cache->free_space_ctl->op->use_bitmap = use_bitmap_op;
+	__btrfs_remove_free_space_cache(cache->free_space_ctl);
+
+	return 0;
+}
+
 int btrfs_test_free_space_cache(void)
 {
 	struct btrfs_block_group_cache *cache;
@@ -386,6 +898,8 @@ int btrfs_test_free_space_cache(void)
 	ret = test_bitmaps_and_extents(cache);
 	if (ret)
 		goto out;
+
+	ret = test_steal_space_from_bitmap_to_extent(cache);
 out:
 	__btrfs_remove_free_space_cache(cache->free_space_ctl);
 	kfree(cache->free_space_ctl);