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-rw-r--r--fs/btrfs/block-rsv.c22
1 files changed, 21 insertions, 1 deletions
diff --git a/fs/btrfs/block-rsv.c b/fs/btrfs/block-rsv.c
index 01b1ce2240bc..c8b7995c33ee 100644
--- a/fs/btrfs/block-rsv.c
+++ b/fs/btrfs/block-rsv.c
@@ -259,6 +259,7 @@ void btrfs_update_global_block_rsv(struct btrfs_fs_info *fs_info)
struct btrfs_block_rsv *block_rsv = &fs_info->global_block_rsv;
struct btrfs_space_info *sinfo = block_rsv->space_info;
u64 num_bytes;
+ unsigned min_items;
/*
* The global block rsv is based on the size of the extent tree, the
@@ -268,7 +269,26 @@ void btrfs_update_global_block_rsv(struct btrfs_fs_info *fs_info)
num_bytes = btrfs_root_used(&fs_info->extent_root->root_item) +
btrfs_root_used(&fs_info->csum_root->root_item) +
btrfs_root_used(&fs_info->tree_root->root_item);
- num_bytes = max_t(u64, num_bytes, SZ_16M);
+
+ /*
+ * We at a minimum are going to modify the csum root, the tree root, and
+ * the extent root.
+ */
+ min_items = 3;
+
+ /*
+ * But we also want to reserve enough space so we can do the fallback
+ * global reserve for an unlink, which is an additional 5 items (see the
+ * comment in __unlink_start_trans for what we're modifying.)
+ *
+ * But we also need space for the delayed ref updates from the unlink,
+ * so its 10, 5 for the actual operation, and 5 for the delayed ref
+ * updates.
+ */
+ min_items += 10;
+
+ num_bytes = max_t(u64, num_bytes,
+ btrfs_calc_insert_metadata_size(fs_info, min_items));
spin_lock(&sinfo->lock);
spin_lock(&block_rsv->lock);