Sigh :-(. Removing optimization prematurely is the root of all evil :-(.

Sorry for the mistake, but the LastDir singleton cache in vfs_ChDir()
actually plays an important role. When we're processing a stream of
SMB1/SMB2/SMB3 requests we don't want to add a chdir()/getcwd()
system call pair on every request if they're all on the same connection
and dealing with the same base path.

I did some testing with a program that times 1,000,000 chdir()
requests vs. 1,000,000 strcmp requests and it's a penalty of 10x
doing the system calls.

Just because it's old code, doesn't mean it's bad :-(.

Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Thu Sep 13 21:31:42 CEST 2012 on sn-devel-104

1 files changed, 13 insertions, 0 deletions

diff --git a/source3/smbd/vfs.c b/source3/smbd/vfs.c
index 7d194404f4..fe99ee29e9 100644
--- a/source3/smbd/vfs.c
+++ b/source3/smbd/vfs.c
@@ -801,14 +801,27 @@ int vfs_ChDir(connection_struct *conn, const char *path)
 {
 	int ret;
 
+	if (!LastDir) {
+		LastDir = SMB_STRDUP("");
+	}
+
 	if (strcsequal(path,".")) {
 		return 0;
 	}
 
+	if (*path == '/' && strcsequal(LastDir,path)) {
+		return 0;
+	}
+
 	DEBUG(4,("vfs_ChDir to %s\n",path));
 
 	ret = SMB_VFS_CHDIR(conn,path);
 	if (ret == 0) {
+		/* Global cache. */
+		SAFE_FREE(LastDir);
+		LastDir = SMB_STRDUP(path);
+
+		/* conn cache. */
 		TALLOC_FREE(conn->cwd);
 		conn->cwd = vfs_GetWd(conn, conn);
 		DEBUG(4,("vfs_ChDir got %s\n",conn->cwd));