[PATCH v2] btrfs: stripe-tree: correctly truncate stripe extents on delete

[Johannes Thumshirn]

From: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>

In our CI system, we're seeing the following ASSERT()ion to trigger when
running RAID stripe-tree tests on non-zoned devices:

 assertion failed: found_start >= start && found_end <= end, in fs/btrfs/raid-stripe-tree.c:64

This ASSERT()ion triggers, because for the initial design of RAID stripe-tree,
I had the "one ordered-extent equals one bio" rule of zoned btrfs in mind.

But for a RAID stripe-tree based system, that is not hosted on a zoned
storage device, but on a regular device this rule doesn't apply.

So in case the range we want to delete starts in the middle of the
previous item, grab the item and "truncate" it's length. That is, subtract
the deleted portion from the key's offset.

In case the range to delete ends in the middle of an item, we have to
adjust both the item's key as well as the stripe extents.

Signed-off-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
---

Changes to v1:
- ASSERT() that slot > 0 before calling btrfs_previous_item()

 fs/btrfs/raid-stripe-tree.c | 52 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 51 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/raid-stripe-tree.c b/fs/btrfs/raid-stripe-tree.c
index 4c859b550f6c..075fecd08d87 100644
--- a/fs/btrfs/raid-stripe-tree.c
+++ b/fs/btrfs/raid-stripe-tree.c
@@ -61,7 +61,57 @@ int btrfs_delete_raid_extent(struct btrfs_trans_handle *trans, u64 start, u64 le
 		trace_btrfs_raid_extent_delete(fs_info, start, end,
 					       found_start, found_end);
 
-		ASSERT(found_start >= start && found_end <= end);
+		if (found_start < start) {
+			struct btrfs_key prev;
+			u64 diff = start - found_start;
+
+			ASSERT(slot > 0);
+
+			ret = btrfs_previous_item(stripe_root, path, start,
+						  BTRFS_RAID_STRIPE_KEY);
+			leaf = path->nodes[0];
+			slot = path->slots[0];
+			btrfs_item_key_to_cpu(leaf, &prev, slot);
+			prev.offset -= diff;
+
+			btrfs_mark_buffer_dirty(trans, leaf);
+
+			start += diff;
+			length -= diff;
+
+			btrfs_release_path(path);
+			continue;
+		}
+
+		if (end < found_end && found_end - end < key.offset) {
+			struct btrfs_stripe_extent *stripe_extent;
+			u64 diff = key.offset - length;
+			int num_stripes;
+
+			num_stripes = btrfs_num_raid_stripes(
+				btrfs_item_size(leaf, slot));
+			stripe_extent = btrfs_item_ptr(
+				leaf, slot, struct btrfs_stripe_extent);
+
+			for (int i = 0; i < num_stripes; i++) {
+				struct btrfs_raid_stride *stride =
+					&stripe_extent->strides[i];
+				u64 physical = btrfs_raid_stride_physical(
+					leaf, stride);
+
+				physical += diff;
+				btrfs_set_raid_stride_physical(leaf, stride,
+							       physical);
+			}
+
+			key.objectid += diff;
+			key.offset -= diff;
+
+			btrfs_mark_buffer_dirty(trans, leaf);
+			btrfs_release_path(path);
+			break;
+		}
+
 		ret = btrfs_del_item(trans, stripe_root, path);
 		if (ret)
 			break;
-- 
2.43.0