s3-vfs: add glusterfs_fuse vfs module.

This module only implements the get_real_filename function by accessing
a distinct extended attribute that is available over a glusterfs fuse
mount.

By implementing this vfs function users of a glusterfs fuse mount
achieve a much better performance in create based workloads where samba
then can avoid trying multiple case folding options to detect the real
filename.

Patch is based on an initial patch provided by
Poornima G <pgurusid@redhat.com>

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13774

Guenther

Signed-off-by: Günther Deschner <gd@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>

Autobuild-User(master): Günther Deschner <gd@samba.org>
Autobuild-Date(master): Tue Jan 22 18:37:56 CET 2019 on sn-devel-144

(cherry picked from commit adffe0dcf002aa4721dc7897261895e3486d5271)

2 files changed, 79 insertions, 0 deletions

diff --git a/source3/modules/vfs_glusterfs_fuse.c b/source3/modules/vfs_glusterfs_fuse.c
new file mode 100644
index 00000000000..64c1b0035c1
--- /dev/null
+++ b/source3/modules/vfs_glusterfs_fuse.c
@@ -0,0 +1,71 @@
+/*
+   Unix SMB/CIFS implementation.
+
+   Copyright (c) 2019 Guenther Deschner <gd@samba.org>
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "includes.h"
+#include "smbd/smbd.h"
+#include "system/filesys.h"
+
+static int vfs_gluster_fuse_get_real_filename(struct vfs_handle_struct *handle,
+					      const char *path,
+					      const char *name,
+					      TALLOC_CTX *mem_ctx,
+					      char **_found_name)
+{
+	int ret;
+	char key_buf[NAME_MAX + 64];
+	char val_buf[NAME_MAX + 1];
+	char *found_name = NULL;
+
+	if (strlen(name) >= NAME_MAX) {
+		errno = ENAMETOOLONG;
+		return -1;
+	}
+
+	snprintf(key_buf, NAME_MAX + 64,
+		 "glusterfs.get_real_filename:%s", name);
+
+	ret = getxattr(path, key_buf, val_buf, NAME_MAX + 1);
+	if (ret == -1) {
+		if (errno == ENODATA) {
+			errno = EOPNOTSUPP;
+		}
+		return -1;
+	}
+
+	found_name = talloc_strdup(mem_ctx, val_buf);
+	if (found_name == NULL) {
+		errno = ENOMEM;
+		return -1;
+	}
+	*_found_name = found_name;
+	return 0;
+}
+
+struct vfs_fn_pointers glusterfs_fuse_fns = {
+
+	/* File Operations */
+	.get_real_filename_fn = vfs_gluster_fuse_get_real_filename,
+};
+
+static_decl_vfs;
+NTSTATUS vfs_glusterfs_fuse_init(TALLOC_CTX *ctx)
+{
+	return smb_register_vfs(SMB_VFS_INTERFACE_VERSION,
+				"glusterfs_fuse", &glusterfs_fuse_fns);
+}
diff --git a/source3/modules/wscript_build b/source3/modules/wscript_build
index 1f9730b5347..23cfa3050d5 100644
--- a/source3/modules/wscript_build
+++ b/source3/modules/wscript_build
@@ -494,6 +494,14 @@ bld.SAMBA3_MODULE('vfs_glusterfs',
                   internal_module=bld.SAMBA3_IS_STATIC_MODULE('vfs_glusterfs'),
                   enabled=bld.SAMBA3_IS_ENABLED_MODULE('vfs_glusterfs'))
 
+bld.SAMBA3_MODULE('vfs_glusterfs_fuse',
+                  subsystem='vfs',
+                  source='vfs_glusterfs_fuse.c',
+                  deps='',
+                  init_function='',
+                  internal_module=bld.SAMBA3_IS_STATIC_MODULE('vfs_glusterfs_fuse'),
+                  enabled=bld.SAMBA3_IS_ENABLED_MODULE('vfs_glusterfs_fuse'))
+
 bld.SAMBA3_MODULE('vfs_worm',
                   subsystem='vfs',
                   source='vfs_worm.c',