btrfs: fix deletion of a range spanning parts two RAID stripe extents

When a user requests the deletion of a range that spans multiple stripe
extents and btrfs_search_slot() returns us the second RAID stripe extent,
we need to pick the previous item and truncate it, if there's still a
range to delete left, move on to the next item.

The following diagram illustrates the operation:

 |--- RAID Stripe Extent ---||--- RAID Stripe Extent ---|
        |--- keep  ---|--- drop ---|

While at it, comment the trivial case of a whole item delete as well.

Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/raid-stripe-tree.c b/fs/btrfs/raid-stripe-tree.c
index ef76202c3a38460c5a36d7309ac0a616f73b0cc0..bf665fdef18b016feca1f784b838a67cdc55e751 100644 (file)
--- a/fs/btrfs/raid-stripe-tree.c
+++ b/fs/btrfs/raid-stripe-tree.c
@@ -99,6 +99,37 @@ int btrfs_delete_raid_extent(struct btrfs_trans_handle *trans, u64 start, u64 le
                found_end = found_start + key.offset;
                ret = 0;
 
+               /*
+                * The stripe extent starts before the range we want to delete,
+                * but the range spans more than one stripe extent:
+                *
+                * |--- RAID Stripe Extent ---||--- RAID Stripe Extent ---|
+                *        |--- keep  ---|--- drop ---|
+                *
+                * This means we have to get the previous item, truncate its
+                * length and then restart the search.
+                */
+               if (found_start > start) {
+                       if (slot == 0) {
+                               ret = btrfs_previous_item(stripe_root, path, start,
+                                                         BTRFS_RAID_STRIPE_KEY);
+                               if (ret) {
+                                       if (ret > 0)
+                                               ret = -ENOENT;
+                                       break;
+                               }
+                       } else {
+                               path->slots[0]--;
+                       }
+
+                       leaf = path->nodes[0];
+                       slot = path->slots[0];
+                       btrfs_item_key_to_cpu(leaf, &key, slot);
+                       found_start = key.objectid;
+                       found_end = found_start + key.offset;
+                       ASSERT(found_start <= start);
+               }
+
                if (key.type != BTRFS_RAID_STRIPE_KEY)
                        break;
 
@@ -152,6 +183,7 @@ int btrfs_delete_raid_extent(struct btrfs_trans_handle *trans, u64 start, u64 le
                        break;
                }
 
+               /* Finally we can delete the whole item, no more special cases. */
                ret = btrfs_del_item(trans, stripe_root, path);
                if (ret)
                        break;