Merge pull request #4761 from MichaelEischer/fix-cache-race

cache: ignore ErrNotExist during cleanup of old files

changelog/unreleased/issue-4760

@@ -0,0 +1,8 @@
+Bugfix: Fix possible error on concurrent cache cleanup
+
+If multiple restic processes concurrently cleaned up no longer existing files
+from the cache, this could cause some of the processes to fail with an `no such
+file or directory` error. This has been fixed.
+
+https://github.com/restic/restic/issues/4760
+https://github.com/restic/restic/pull/4761

internal/cache/file.go

@@ -165,7 +165,8 @@ func (c *Cache) Clear(t restic.FileType, valid restic.IDSet) error {
 			continue
 		}
 
-		if err = fs.Remove(c.filename(backend.Handle{Type: t, Name: id.String()})); err != nil {
+		// ignore ErrNotExist to gracefully handle multiple processes running Clear() concurrently
+		if err = fs.Remove(c.filename(backend.Handle{Type: t, Name: id.String()})); err != nil && !errors.Is(err, os.ErrNotExist) {
 			return err
 		}
 	}