From 2e086a73458aa174ea074fbe95cd690d0df3e192 Mon Sep 17 00:00:00 2001
From: Marco van Wieringen <mvw@planets.elm.net>
Date: Sat, 12 Nov 2011 09:59:54 +0100
Subject: [PATCH] Change locking scheme of the mountpoint cache.

We now lock the mount cache from the moment a caller enters
find_mntent_mapping. This way we know for sure no one can
be tampering our structures until we finish. As flush_mntent_cache
is not called from the outside and now is a function which needs
the lock hold we remove it as an external interface.
---
 bacula/src/lib/mntent_cache.c | 44 +++++++++++------------------------
 bacula/src/lib/mntent_cache.h |  1 -
 2 files changed, 14 insertions(+), 31 deletions(-)

diff --git a/bacula/src/lib/mntent_cache.c b/bacula/src/lib/mntent_cache.c
index 6d76239980..75eefe2abf 100644
--- a/bacula/src/lib/mntent_cache.c
+++ b/bacula/src/lib/mntent_cache.c
@@ -348,14 +348,10 @@ static void clear_mount_cache()
 
 /**
  * Initialize the cache for use.
+ * This function should be called with a write lock on the mntent_cache.
  */
 static void initialize_mntent_cache(void)
 {
-   /**
-    * Lock the cache while we update it.
-    */
-   P(mntent_cache_lock);
-
    /**
     * Make sure the cache is empty (either by flushing it or by initializing it.)
     */
@@ -365,29 +361,18 @@ static void initialize_mntent_cache(void)
     * Refresh the cache.
     */
    refresh_mount_cache();
-
-   /**
-    * We are done updating the cache.
-    */
-   V(mntent_cache_lock);
 }
 
-void flush_mntent_cache(void)
+/**
+ * Flush the current content from the cache.
+ * This function should be called with a write lock on the mntent_cache.
+ */
+static void flush_mntent_cache(void)
 {
-   /**
-    * Lock the cache while we update it.
-    */
-   P(mntent_cache_lock);
-
    /**
     * Make sure the cache is empty (either by flushing it or by initializing it.)
     */
    clear_mount_cache();
-
-   /**
-    * We are done updating the cache.
-    */
-   V(mntent_cache_lock);
 }
 
 /**
@@ -398,11 +383,17 @@ mntent_cache_entry_t *find_mntent_mapping(uint32_t dev)
    mntent_cache_entry_t *mce = NULL;
    time_t now;
 
+   /**
+    * Lock the cache.
+    */
+   P(mntent_cache_lock);
+
    /**
     * Shortcut when we get a request for the same device again.
     */
    if (previous_cache_hit && previous_cache_hit->dev == dev) {
-      return previous_cache_hit;
+      mce = previous_cache_hit;
+      goto ok_out;
    }
 
    /**
@@ -424,11 +415,6 @@ mntent_cache_entry_t *find_mntent_mapping(uint32_t dev)
       }
    }
 
-   /**
-    * Lock the cache while we walk it.
-    */
-   P(mntent_cache_lock);
-
    mce = (mntent_cache_entry_t *)mntent_cache_entry_hashtable->lookup(dev);
 
    /**
@@ -457,9 +443,7 @@ mntent_cache_entry_t *find_mntent_mapping(uint32_t dev)
       previous_cache_hit = mce;
    }
 
-   /**
-    * We are done walking the cache.
-    */
+ok_out:
    V(mntent_cache_lock);
    return mce;
 }
diff --git a/bacula/src/lib/mntent_cache.h b/bacula/src/lib/mntent_cache.h
index 82c2f64f1f..8e1e79d67d 100644
--- a/bacula/src/lib/mntent_cache.h
+++ b/bacula/src/lib/mntent_cache.h
@@ -60,6 +60,5 @@ struct mntent_cache_entry_t {
 };
 
 mntent_cache_entry_t *find_mntent_mapping(uint32_t dev);
-void flush_mntent_cache(void);
 
 #endif /* _MNTENT_CACHE_H */
-- 
2.39.2