From: Anders Kaseorg <andersk@mit.edu>
Date: Tue, 7 May 2013 04:27:33 +0000 (-0400)
Subject: Linux: osi_TryEvictVCache: Don’t skip the first dentry if D_ALIAS_IS_HLIST
X-Git-Tag: upstream/1.6.3^2~7
X-Git-Url: https://git.michaelhowe.org/gitweb/?a=commitdiff_plain;h=a71cc5511c115c1b6cb4a6a2997a846bab6e19e2;p=packages%2Fo%2Fopenafs.git

Linux: osi_TryEvictVCache: Don’t skip the first dentry if D_ALIAS_IS_HLIST

An hlist doesn’t begin with a sentinel like a list does, so the old
code would skip the first dentry or crash with a NULL dereference if
there wasn’t one.  Use the kernel’s list_for_each_entry or
hlist_for_each_entry macros instead of trying to do it manually.

Should fix a crash observed by Alex Chernyakhovsky on kernel 3.6 and
newer.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Reviewed-on: http://gerrit.openafs.org/9857
Reviewed-by: Alex Chernyakhovsky <achernya@mit.edu>
Tested-by: Alex Chernyakhovsky <achernya@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Marc Dionne <marc.c.dionne@gmail.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit ad6e31d5fea221bf5eefcd35a416667bc7c1f9be)

Change-Id: Id8b31246067b5a718af91c8c206d5abd5210c558
Reviewed-on: http://gerrit.openafs.org/9898
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Marc Dionne <marc.c.dionne@gmail.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
---

diff --git a/src/afs/LINUX/osi_vcache.c b/src/afs/LINUX/osi_vcache.c
index dc3685b63..99aab919d 100644
--- a/src/afs/LINUX/osi_vcache.c
+++ b/src/afs/LINUX/osi_vcache.c
@@ -19,10 +19,8 @@ osi_TryEvictVCache(struct vcache *avc, int *slept, int defersleep) {
 
     struct dentry *dentry;
     struct inode *inode = AFSTOV(avc);
-#if defined(D_ALIAS_IS_HLIST)
-    struct hlist_node *cur, *head, *list_end;
-#else
-    struct list_head *cur, *head, *list_end;
+#if defined(D_ALIAS_IS_HLIST) && !defined(HLIST_ITERATOR_NO_NODE)
+    struct hlist_node *p;
 #endif
 
     /* First, see if we can evict the inode from the dcache */
@@ -33,13 +31,9 @@ osi_TryEvictVCache(struct vcache *avc, int *slept, int defersleep) {
 
 #if defined(HAVE_DCACHE_LOCK)
         spin_lock(&dcache_lock);
-	head = &inode->i_dentry;
 
 restart:
-        cur = head;
-	while ((cur = cur->next) != head) {
-	    dentry = list_entry(cur, struct dentry, d_alias);
-
+	list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
 	    if (d_unhashed(dentry))
 		continue;
 	    dget_locked(dentry);
@@ -57,23 +51,17 @@ restart:
 	spin_unlock(&dcache_lock);
 #else /* HAVE_DCACHE_LOCK */
 	spin_lock(&inode->i_lock);
-#if defined(D_ALIAS_IS_HLIST)
-	head = inode->i_dentry.first;
-	list_end = NULL;
-#else
-	head = &inode->i_dentry;
-	list_end = head;
-#endif
 
 restart:
-	cur = head;
-	while ((cur = cur->next) != list_end) {
 #if defined(D_ALIAS_IS_HLIST)
-	    dentry = hlist_entry(cur, struct dentry, d_alias);
+# if defined(HLIST_ITERATOR_NO_NODE)
+	hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) {
+# else
+	hlist_for_each_entry(dentry, p, &inode->i_dentry, d_alias) {
+# endif
 #else
-	    dentry = list_entry(cur, struct dentry, d_alias);
+	list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
 #endif
-
 	    spin_lock(&dentry->d_lock);
 	    if (d_unhashed(dentry)) {
 		spin_unlock(&dentry->d_lock);