From: Michael Vrable <mvrable@cs.ucsd.edu>
Date: Fri, 19 Mar 2010 22:59:00 +0000 (-0700)
Subject: Make dropping of inodes from cache more resistant to races.
X-Git-Url: https://git.vrable.net/?a=commitdiff_plain;h=767a8a1be7012ca1445a62b61873f3bfdb719b13;p=bluesky.git

Make dropping of inodes from cache more resistant to races.
---

diff --git a/bluesky/cache.c b/bluesky/cache.c
index 481390f..8d2cda1 100644
--- a/bluesky/cache.c
+++ b/bluesky/cache.c
@@ -58,15 +58,18 @@ static void flushd_inode(gpointer value, gpointer user_data)
             drop_caches(inode);
 
             /* If the only references are the one we hold and the one in the
-             * filesystem inum->inode hash table...  The check for a refcount
-             * of 2 shouldn't be necessary so it should be okay if there is a
-             * race on the check. */
+             * filesystem inum->inode hash table...  First check the refcount
+             * without the lock for speed, but if the check looks good verify
+             * it after taking the filesystem lock. */
             if (inode->refcount == 2) {
-                g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG,
-                      "Trying to drop inode %"PRIu64" from cache", inode->inum);
                 g_mutex_lock(fs->lock);
-                if (g_hash_table_remove(fs->inodes, &inode->inum))
-                    bluesky_inode_unref(inode);
+                if (inode->refcount == 2) {
+                    g_log("bluesky/flushd", G_LOG_LEVEL_DEBUG,
+                          "Trying to drop inode %"PRIu64" from cache",
+                          inode->inum);
+                    if (g_hash_table_remove(fs->inodes, &inode->inum))
+                        bluesky_inode_unref(inode);
+                }
                 g_mutex_unlock(fs->lock);
             }
         }