ext4: support xattr gnu.* namespace for the Hurd

PATCH Superseded Jan (janneke) Nieuwenhuizen 1 participant 1 message May 18, 2020 ext4 file system

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Jan (janneke) Nieuwenhuizen

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2020-05-18 06:07 UTC #0 lore raw

PATCH 1/1 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

fs/ext4/Kconfig +11 -0

index 2a592e38cdfe..e08f818eec4c 100644
@@ -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

fs/ext4/Makefile +1 -0

index 4ccb3c9189d8..3c2c43167dbf 100644
@@ -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

fs/ext4/xattr.c +6 -0

index 21df43a25328..084361183a55 100644
@@ -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
 };

fs/ext4/xattr.h +1 -0

index ffe21ac77f78..730b91fa0dd7 100644
@@ -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"

fs/ext4/xattr_hurd.c new file +57 -0

57 lines not on this page · raw message

include/uapi/linux/xattr.h +4 -0

index c1395b5bd432..9463db2dfa9d 100644
@@ -7,6 +7,7 @@
   Copyright (C) 2001 by Andreas Gruenbacher <[email protected]>
   Copyright (c) 2001-2002 Silicon Graphics, Inc.  All Rights Reserved.
   Copyright (c) 2004 Red Hat, Inc., James Morris <[email protected]>
+  Copyright (c) 2020 Jan (janneke) Nieuwenhuizen <[email protected]>
 */
 
 #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)

Signature · 1 line

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