Improve clean up algorithm to avoid redundant unlinks

Also adds comment about the needed clean up order.

diff --git a/cleanup.c b/cleanup.c
index f38ccbca2222e060fead73e95795007c20124349..c267de480da862e00194bd7460f9cd5dac4cca87 100644 (file)
--- a/cleanup.c
+++ b/cleanup.c
@@ -158,9 +158,10 @@ static void sort_and_clean(void)
 {
        unsigned i;
        const char *ext;
+       char *last_base = x_strdup("");
 
        if (num_files > 1) {
-               /* sort in ascending data order */
+               /* Sort in ascending mtime order. */
                qsort(files, num_files, sizeof(struct files *),
                      (COMPAR_FN_T)files_compare);
        }
@@ -168,39 +169,39 @@ static void sort_and_clean(void)
        /* delete enough files to bring us below the threshold */
        for (i = 0; i < num_files; i++) {
                if ((object_size_threshold == 0
-                    || total_object_size < object_size_threshold)
+                    || total_object_size <= object_size_threshold)
                    && (object_files_threshold == 0
-                       || (num_files-i) < object_files_threshold)) {
+                       || total_object_files <= object_files_threshold)) {
                        break;
                }
 
-               delete_file(files[i]->fname, files[i]->size);
-
                ext = get_extension(files[i]->fname);
-               if (strcmp(ext, ".manifest") == 0) {
-                       /* Nothing more to do. */
-               } else {
-                       /*
-                        * Make sure that any sibling files are deleted as
-                        * well.
-                        */
+               if (strcmp(ext, ".o") == 0
+                   || strcmp(ext, ".d") == 0
+                   || strcmp(ext, ".stderr") == 0
+                   || strcmp(ext, "") == 0) {
                        char *base = remove_extension(files[i]->fname);
-                       if (strcmp(ext, "") != 0) {
-                               /* Object file from ccache 2.4. */
-                               delete_sibling_file(base, "");
-                       }
-                       if (strcmp(ext, ".d") != 0) {
-                               delete_sibling_file(base, ".d");
-                       }
-                       if (strcmp(ext, ".o") != 0) {
+                       if (strcmp(base, last_base) != 0) { /* Avoid redundant unlinks. */
+                               /*
+                                * Make sure that all sibling files are deleted so that a cached result
+                                * is removed completely. Note the order of deletions -- the stderr
+                                * file must be deleted last because if the ccache process gets killed
+                                * after deleting the .stderr but before deleting the .o, the cached
+                                * result would be inconsistent.
+                                */
                                delete_sibling_file(base, ".o");
-                       }
-                       if (strcmp(ext, ".stderr") != 0) {
+                               delete_sibling_file(base, ".d");
                                delete_sibling_file(base, ".stderr");
+                               delete_sibling_file(base, ""); /* Object file from ccache 2.4. */
                        }
-                       free(base);
+                       free(last_base);
+                       last_base = base;
+               } else {
+                       /* .manifest or unknown file. */
+                       delete_file(files[i]->fname, files[i]->size);
                }
        }
+       free(last_base);
 }
 
 /* cleanup in one cache subdir */