Disk Cache: Add a histogram to track list head corruption.

BUG=none
TEST=none
Review URL: https://chromiumcodereview.appspot.com/10561012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@142996 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 49 insertions, 1 deletions

diff --git a/net/disk_cache/rankings.cc b/net/disk_cache/rankings.cc
index a14a37a..99ed927 100644
--- a/net/disk_cache/rankings.cc
+++ b/net/disk_cache/rankings.cc
@@ -492,6 +492,8 @@ int Rankings::SelfCheck() {
     total += partial;
   }
   CACHE_UMA(AGE_MS, "ListSelfCheckTime", 0, start);
+
+  QuickListCheck();
   return total;
 }
 
@@ -785,7 +787,7 @@ int Rankings::CheckList(List list) {
   int head_items;
   int rv = CheckListSection(list, last1, last2, true,  // Head to tail.
                             &last1, &last2, &head_items);
-  if (rv == 0)
+  if (rv == ERR_NO_ERROR)
     return head_items;
 
   Addr last3, last4;
@@ -896,6 +898,48 @@ int Rankings::CheckListSection(List list, Addr end1, Addr end2, bool forward,
   return ERR_NO_ERROR;
 }
 
+// TODO(rvargas): remove when we figure why we have corrupt heads.
+void Rankings::QuickListCheck() {
+  for (int i = 0; i < LAST_ELEMENT; i++) {
+    int rv = CheckHeadAndTail(static_cast<List>(i));
+    CACHE_UMA(CACHE_ERROR, "QuickListCheck", 0, rv);
+  }
+}
+
+int Rankings::CheckHeadAndTail(List list) {
+  Addr head_addr = heads_[list];
+  Addr tail_addr = tails_[list];
+
+  if (!head_addr.is_initialized() && !tail_addr.is_initialized())
+    return ERR_NO_ERROR;
+
+  if (!head_addr.SanityCheckForRankings())
+    return ERR_INVALID_HEAD;
+
+  if (!tail_addr.SanityCheckForRankings())
+    return ERR_INVALID_TAIL;
+
+  scoped_ptr<CacheRankingsBlock> head;
+  head.reset(new CacheRankingsBlock(backend_->File(head_addr), head_addr));
+  head->Load();
+  if (!SanityCheck(head.get(), true))  // From list.
+      return ERR_INVALID_ENTRY;
+
+  scoped_ptr<CacheRankingsBlock> tail;
+  tail.reset(new CacheRankingsBlock(backend_->File(tail_addr), tail_addr));
+  tail->Load();
+  if (!SanityCheck(tail.get(), true))  // From list.
+    return ERR_INVALID_ENTRY;
+
+  if (head->Data()->prev != head_addr.value())
+    return ERR_INVALID_PREV;
+
+  if (tail->Data()->next != tail_addr.value())
+    return ERR_INVALID_NEXT;
+
+  return ERR_NO_ERROR;
+}
+
 bool Rankings::IsHead(CacheAddr addr, List* list) const {
   for (int i = 0; i < LAST_ELEMENT; i++) {
     if (addr == heads_[i].value()) {
diff --git a/net/disk_cache/rankings.h b/net/disk_cache/rankings.h
index b20e3f1..0886e0c 100644
--- a/net/disk_cache/rankings.h
+++ b/net/disk_cache/rankings.h
@@ -181,6 +181,10 @@ class Rankings {
   // and the addresses of the last nodes visited.
   int CheckListSection(List list, Addr end1, Addr end2, bool forward,
                        Addr* last, Addr* second_last, int* num_items);
+  void QuickListCheck();
+
+  // Returns an error code as appropriate.
+  int CheckHeadAndTail(List list);
 
   // Returns true if addr is the head or tail of any list. When there is a
   // match |list| will contain the list number for |addr|.