[PATCH v3 3/8] sparse-index: silently return when cache tree fails

From: Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Date: Aug 17, 2021, 13:23 UTC
Message-ID: <371985352680a767dfacb5477aa77e92e04008ee.1629206603.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.1009.v3.git.1629206602.gitgitgadget@gmail.com>

From: Derrick Stolee <dstolee@microsoft.com>

If cache_tree_update() returns a non-zero value, then it could not create the cache tree. This is likely due to a path having a merge conflict. Since we are already returning early, let's return silently to avoid making it seem like we failed to write the index at all.

If we remove our dependence on the cache tree within convert_to_sparse(), then we could still recover from this scenario and have a sparse index.

When constructing the cache-tree extension in convert_to_sparse(), it is possible that we construct a tree object that is new to the object database. Without the WRITE_TREE_MISSING_OK flag, this results in an error that halts our conversion to a sparse index. Add this flag to remove this limitation.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 sparse-index.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/sparse-index.c b/sparse-index.c
index bc5900eae35..b6e90417556 100644
--- a/sparse-index.c
+++ b/sparse-index.c
@@ -179,10 +179,15 @@ int convert_to_sparse(struct index_state *istate)
 
 	/* Clear and recompute the cache-tree */
 	cache_tree_free(&istate->cache_tree);
-	if (cache_tree_update(istate, 0)) {
-		warning(_("unable to update cache-tree, staying full"));
-		return -1;
-	}
+	/*
+	 * Silently return if there is a problem with the cache tree update,
+	 * which might just be due to a conflict state in some entry.
+	 *
+	 * This might create new tree objects, so be sure to use
+	 * WRITE_TREE_MISSING_OK.
+	 */
+	if (cache_tree_update(istate, WRITE_TREE_MISSING_OK))
+		return 0;
 
 	remove_fsmonitor(istate);

-- 
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