Fix cache algorithm loophole

This closes the door for unneccessary calls to cgit_fill_cache().

Noticed by Linus.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

3 files changed, 16 insertions, 11 deletions

diff --git a/cache.c b/cache.c
index b034c48..0ffa502 100644
--- a/cache.c
+++ b/cache.c
@@ -7,13 +7,13 @@
  */
 
 #include "cgit.h"
 
 const int NOLOCK = -1;
 
-int cache_lookup(struct cacheitem *item)
+void cache_prepare(struct cacheitem *item)
 {
 	if (!cgit_query_repo) {
 		item->name = xstrdup(fmt("%s/index.html", cgit_cache_root));
 		item->ttl = cgit_cache_root_ttl;
 	} else if (!cgit_query_page) {
 		item->name = xstrdup(fmt("%s/%s/index.html", cgit_cache_root, 
@@ -27,12 +27,16 @@ int cache_lookup(struct cacheitem *item)
 			item->ttl = cgit_cache_dynamic_ttl;
 		else if (cgit_query_has_sha1)
 			item->ttl = cgit_cache_static_ttl;
 		else
 			item->ttl = cgit_cache_repo_ttl;
 	}
+}
+
+int cache_exist(struct cacheitem *item)
+{
 	if (stat(item->name, &item->st)) {
 		item->st.st_mtime = 0;
 		return 0;
 	}
 	return 1;
 }
diff --git a/cgit.c b/cgit.c
index 110face..7f14016 100644
--- a/cgit.c
+++ b/cgit.c
@@ -462,26 +462,26 @@ static void cgit_fill_cache(struct cacheitem *item)
 	else
 		cgit_print_repolist();
 }
 
 static void cgit_refresh_cache(struct cacheitem *item)
 {
+	cache_prepare(item);
  top:
-	if (!cache_lookup(item)) {
-		if (cache_lock(item)) {
-			cgit_fill_cache(item);
-			cache_unlock(item);
-		} else {
+	if (!cache_exist(item)) {
+		if (!cache_lock(item)) {
 			sched_yield();
 			goto top;
 		}
-	} else if (cache_expired(item)) {
-		if (cache_lock(item)) {
+		if (!cache_exist(item))
 			cgit_fill_cache(item);
-			cache_unlock(item);
-		}
+		cache_unlock(item);
+	} else if (cache_expired(item) && cache_lock(item)) {
+		if (cache_expired(item))
+			cgit_fill_cache(item);
+		cache_unlock(item);
 	}
 }
 
 static void cgit_print_cache(struct cacheitem *item)
 {
 	static char buf[4096];
diff --git a/cgit.h b/cgit.h
index 1e084d4..3b0994a 100644
--- a/cgit.h
+++ b/cgit.h
@@ -53,12 +53,13 @@ extern void html_attr(char *txt);
 extern void html_link_open(char *url, char *title, char *class);
 extern void html_link_close(void);
 
 
 extern int cgit_read_config(const char *filename, configfn fn);
 
-extern int cache_lookup(struct cacheitem *item);
+extern void cache_prepare(struct cacheitem *item);
 extern int cache_lock(struct cacheitem *item);
 extern int cache_unlock(struct cacheitem *item);
+extern int cache_exist(struct cacheitem *item);
 extern int cache_expired(struct cacheitem *item);
 
 #endif /* CGIT_H */