afs: Fix afs_d_validate() to set the right directory version

If a dentry's version is somewhere between invalid_before and the current
directory version, we should be setting it forward to the current version,
not backwards to the invalid_before version.  Note that we're only doing
this at all because dentry::d_fsdata isn't large enough on a 32-bit system.

Fix this by using a separate variable for invalid_before so that we don't
accidentally clobber the current dir version.

Fixes: a4ff7401 ("afs: Keep track of invalid-before version for dentry coherency")
Signed-off-by: David Howells <dhowells@redhat.com>

fs/afs/dir.c

@@ -1032,7 +1032,7 @@ static int afs_d_revalidate(struct dentry *dentry, unsigned int flags)
 	struct dentry *parent;
 	struct inode *inode;
 	struct key *key;
-	afs_dataversion_t dir_version;
+	afs_dataversion_t dir_version, invalid_before;
 	long de_version;
 	int ret;
 
@@ -1084,8 +1084,8 @@ static int afs_d_revalidate(struct dentry *dentry, unsigned int flags)
 	if (de_version == (long)dir_version)
 		goto out_valid_noupdate;
 
-	dir_version = dir->invalid_before;
-	if (de_version - (long)dir_version >= 0)
+	invalid_before = dir->invalid_before;
+	if (de_version - (long)invalid_before >= 0)
 		goto out_valid;
 
 	_debug("dir modified");