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Message-Id: <20200518060734.7159-1-janneke@gnu.org>
Date: Mon, 18 May 2020 08:07:34 +0200
From: "Jan (janneke) Nieuwenhuizen" <janneke@....org>
To: linux-ext4@...r.kernel.org, Theodore Ts'o <tytso@....edu>,
Andreas Dilger <adilger.kernel@...ger.ca>
Cc: Danny Milosavljevic <dannym@...atchpost.org>,
Samuel Thibault <samuel.thibault@....org>
Subject: [PATCH] ext4: support xattr gnu.* namespace for the Hurd
The Hurd gained[0] support for moving the translator and author
fields out of the inode and into the "gnu.*" xattr namespace.
In anticipation of that, an xattr INDEX was reserved[1]. The Hurd has
now been brought into compliance[2] with that.
This patch adds support for reading and writing such attributes from
Linux; you can now do something like
dd if=/dev/zero of=file bs=1k count=1000
losetup /dev/loop0 file
mke2fs -t ext2 -o hurd -O ext_attr /dev/loop0
mount -t ext2 /dev/loop0 /mnt
mkdir -p /mnt/servers/socket
touch /mnt/servers/socket/1
setfattr --name=gnu.translator --value='"/hurd/pflocal\0"' \
/mnt/servers/socket/1
getfattr --name=gnu.translator /mnt/servers/socket/1
# file: 1
gnu.translator="/hurd/pflocal"
to setup a pipe translator, which is being used to create[3] a
vm-image for the Hurd from GNU Guix.
[0] https://summerofcode.withgoogle.com/projects/#5869799859027968
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3980bd3b406addb327d858aebd19e229ea340b9a
[2] https://git.savannah.gnu.org/cgit/hurd/hurd.git/commit/?id=a04c7bf83172faa7cb080fbe3b6c04a8415ca645
[3] https://git.savannah.gnu.org/cgit/guix.git/log/?h=wip-hurd-vm
---
fs/ext4/Kconfig | 11 ++++++++
fs/ext4/Makefile | 1 +
fs/ext4/xattr.c | 6 ++++
fs/ext4/xattr.h | 1 +
fs/ext4/xattr_hurd.c | 57 ++++++++++++++++++++++++++++++++++++++
include/uapi/linux/xattr.h | 4 +++
6 files changed, 80 insertions(+)
create mode 100644 fs/ext4/xattr_hurd.c
diff --git a/fs/ext4/Kconfig b/fs/ext4/Kconfig
index 2a592e38cdfe..e08f818eec4c 100644
--- a/fs/ext4/Kconfig
+++ b/fs/ext4/Kconfig
@@ -92,6 +92,17 @@ config EXT4_FS_SECURITY
If you are not using a security module that requires using
extended attributes for file security labels, say N.
+config EXT4_FS_HURD
+ bool "Ext4 xattr gnu.* namespace support for the Hurd"
+ depends on EXT4_FS
+ help
+ Extended attributes are name:value pairs associated with inodes by
+ the kernel or by users (see the attr(5) manual page for details).
+ This option adds support for the gnu.* namespace ext4 file
+ systems for the Hurd.
+
+ If you don't know what the GNU Hurd is, say N
+
config EXT4_DEBUG
bool "Ext4 debugging support"
depends on EXT4_FS
diff --git a/fs/ext4/Makefile b/fs/ext4/Makefile
index 4ccb3c9189d8..3c2c43167dbf 100644
--- a/fs/ext4/Makefile
+++ b/fs/ext4/Makefile
@@ -16,3 +16,4 @@ ext4-$(CONFIG_EXT4_FS_SECURITY) += xattr_security.o
ext4-inode-test-objs += inode-test.o
obj-$(CONFIG_EXT4_KUNIT_TESTS) += ext4-inode-test.o
ext4-$(CONFIG_FS_VERITY) += verity.o
+ext4-$(CONFIG_EXT4_FS_HURD) += xattr_hurd.o
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 21df43a25328..084361183a55 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -93,6 +93,9 @@ static const struct xattr_handler * const ext4_xattr_handler_map[] = {
#ifdef CONFIG_EXT4_FS_SECURITY
[EXT4_XATTR_INDEX_SECURITY] = &ext4_xattr_security_handler,
#endif
+#ifdef CONFIG_EXT4_FS_HURD
+ [EXT4_XATTR_INDEX_HURD] = &ext4_xattr_hurd_handler,
+#endif
};
const struct xattr_handler *ext4_xattr_handlers[] = {
@@ -104,6 +107,9 @@ const struct xattr_handler *ext4_xattr_handlers[] = {
#endif
#ifdef CONFIG_EXT4_FS_SECURITY
&ext4_xattr_security_handler,
+#endif
+#ifdef CONFIG_EXT4_FS_HURD
+ &ext4_xattr_hurd_handler,
#endif
NULL
};
diff --git a/fs/ext4/xattr.h b/fs/ext4/xattr.h
index ffe21ac77f78..730b91fa0dd7 100644
--- a/fs/ext4/xattr.h
+++ b/fs/ext4/xattr.h
@@ -124,6 +124,7 @@ struct ext4_xattr_inode_array {
extern const struct xattr_handler ext4_xattr_user_handler;
extern const struct xattr_handler ext4_xattr_trusted_handler;
extern const struct xattr_handler ext4_xattr_security_handler;
+extern const struct xattr_handler ext4_xattr_hurd_handler;
#define EXT4_XATTR_NAME_ENCRYPTION_CONTEXT "c"
diff --git a/fs/ext4/xattr_hurd.c b/fs/ext4/xattr_hurd.c
new file mode 100644
index 000000000000..bc97cdcd5e65
--- /dev/null
+++ b/fs/ext4/xattr_hurd.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/fs/ext4/xattr_hurd.c
+ * Handler for extended gnu attributes for the Hurd.
+ *
+ * Copyright (C) 2001 by Andreas Gruenbacher, <a.gruenbacher@...puter.org>
+ * Copyright (C) 2020 by Jan (janneke) Nieuwenhuizen, <janneke@....org>
+ */
+
+#include <linux/init.h>
+#include <linux/string.h>
+#include "ext4.h"
+#include "xattr.h"
+
+static bool
+ext4_xattr_hurd_list(struct dentry *dentry)
+{
+ return test_opt(dentry->d_sb, XATTR_USER) &&
+ EXT4_SB(dentry->d_sb)->s_es->s_creator_os ==
+ cpu_to_le32(EXT4_OS_HURD);
+}
+
+static int
+ext4_xattr_hurd_get(const struct xattr_handler *handler,
+ struct dentry *unused, struct inode *inode,
+ const char *name, void *buffer, size_t size)
+{
+ if (!test_opt(inode->i_sb, XATTR_USER) ||
+ EXT4_SB(inode->i_sb)->s_es->s_creator_os !=
+ cpu_to_le32(EXT4_OS_HURD))
+ return -EOPNOTSUPP;
+
+ return ext4_xattr_get(inode, EXT4_XATTR_INDEX_HURD,
+ name, buffer, size);
+}
+
+static int
+ext4_xattr_hurd_set(const struct xattr_handler *handler,
+ struct dentry *unused, struct inode *inode,
+ const char *name, const void *value,
+ size_t size, int flags)
+{
+ if (!test_opt(inode->i_sb, XATTR_USER) ||
+ EXT4_SB(inode->i_sb)->s_es->s_creator_os !=
+ cpu_to_le32(EXT4_OS_HURD))
+ return -EOPNOTSUPP;
+
+ return ext4_xattr_set(inode, EXT4_XATTR_INDEX_HURD,
+ name, value, size, flags);
+}
+
+const struct xattr_handler ext4_xattr_hurd_handler = {
+ .prefix = XATTR_HURD_PREFIX,
+ .list = ext4_xattr_hurd_list,
+ .get = ext4_xattr_hurd_get,
+ .set = ext4_xattr_hurd_set,
+};
diff --git a/include/uapi/linux/xattr.h b/include/uapi/linux/xattr.h
index c1395b5bd432..9463db2dfa9d 100644
--- a/include/uapi/linux/xattr.h
+++ b/include/uapi/linux/xattr.h
@@ -7,6 +7,7 @@
Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@...puter.org>
Copyright (c) 2001-2002 Silicon Graphics, Inc. All Rights Reserved.
Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@...hat.com>
+ Copyright (c) 2020 Jan (janneke) Nieuwenhuizen <janneke@....org>
*/
#include <linux/libc-compat.h>
@@ -31,6 +32,9 @@
#define XATTR_BTRFS_PREFIX "btrfs."
#define XATTR_BTRFS_PREFIX_LEN (sizeof(XATTR_BTRFS_PREFIX) - 1)
+#define XATTR_HURD_PREFIX "gnu."
+#define XATTR_HURD_PREFIX_LEN (sizeof(XATTR_HURD_PREFIX) - 1)
+
#define XATTR_SECURITY_PREFIX "security."
#define XATTR_SECURITY_PREFIX_LEN (sizeof(XATTR_SECURITY_PREFIX) - 1)
--
2.26.2
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