lkml.org 
[lkml]   [2001]   [Nov]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [RFC][PATCH] VFS interface for extended attributes
On Tue, Nov 13, 2001 at 06:27:11AM +0100, Andi Kleen wrote:
> On Mon, Nov 12, 2001 at 07:32:18PM -0500, Alexander Viro wrote:
> > Which means that converting permission() to vfsmount/dentry should be
> > done first. And that's not hard to do.
>
> It's just messy as it will require changes in all file systems.
>
> > Sorry, folks, but idea of private extendable syscall table (per-filesystem,
> > no less) doesn't look like a good thing. That's _the_ reason why ioctl()
> > is bad.
>
> Unless I'm badly misreading the patch the op switch() is fixed in VFS mapping
> to clearly defined inode operations. It is not extensible per filesystem.
> Arguably they could be split into individual syscalls, but it looks not more
> like cosmetics at this point.

hi Al,

Below is an initial attempt at an interface which doesn't have a
command parameter at all, instead using separate syscalls as Andi
has suggested - is this closer to what you had in mind?

To prevent an exponential increase in the number of syscalls used,
it uses a flag parameter to distinguish similar operations and also
to combine the follow-symlink-or-not cases - it now uses six system
calls instead of the original three.

It also moves the individual VFS extended attribute operations out
into a separate ops vector for a little more interface clarity, not
sure if thats better/worse. The patch ignores the problem of using
dentry vs. inode for now.

Thanks for the suggestions - I'd be interested in any thoughts you
have on this one as well.

cheers.

--
Nathan


diff -Naur 2.4.14-pristine/arch/i386/kernel/entry.S 2.4.14-al/arch/i386/kernel/entry.S
--- 2.4.14-pristine/arch/i386/kernel/entry.S Sat Nov 3 12:18:49 2001
+++ 2.4.14-al/arch/i386/kernel/entry.S Tue Nov 13 15:54:55 2001
@@ -622,6 +622,12 @@
.long SYMBOL_NAME(sys_ni_syscall) /* Reserved for Security */
.long SYMBOL_NAME(sys_gettid)
.long SYMBOL_NAME(sys_readahead) /* 225 */
+ .long SYMBOL_NAME(sys_setxattr)
+ .long SYMBOL_NAME(sys_fsetxattr)
+ .long SYMBOL_NAME(sys_getxattr)
+ .long SYMBOL_NAME(sys_fgetxattr)
+ .long SYMBOL_NAME(sys_listxattr) /* 230 */
+ .long SYMBOL_NAME(sys_flistxattr)

.rept NR_syscalls-(.-sys_call_table)/4
.long SYMBOL_NAME(sys_ni_syscall)
diff -Naur 2.4.14-pristine/fs/Makefile 2.4.14-al/fs/Makefile
--- 2.4.14-pristine/fs/Makefile Tue Nov 6 08:40:59 2001
+++ 2.4.14-al/fs/Makefile Fri Nov 9 15:27:42 2001
@@ -14,7 +14,7 @@
super.o block_dev.o char_dev.o stat.o exec.o pipe.o namei.o \
fcntl.o ioctl.o readdir.o select.o fifo.o locks.o \
dcache.o inode.o attr.o bad_inode.o file.o iobuf.o dnotify.o \
- filesystems.o namespace.o
+ filesystems.o namespace.o extattr.o

ifeq ($(CONFIG_QUOTA),y)
obj-y += dquot.o
diff -Naur 2.4.14-pristine/fs/extattr.c 2.4.14-al/fs/extattr.c
--- 2.4.14-pristine/fs/extattr.c Thu Jan 1 10:00:00 1970
+++ 2.4.14-al/fs/extattr.c Tue Nov 13 15:52:51 2001
@@ -0,0 +1,184 @@
+/*
+ File: fs/extattr.c
+
+ Extended attribute handling.
+
+ Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>
+ Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>
+ */
+
+#include <linux/mm.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/smp_lock.h>
+#include <linux/extattr.h>
+
+
+/*
+ * Extended attribute SET operations
+ */
+static long
+setxattr(struct inode *i, char *name, void *value, size_t size, int flags)
+{
+ struct xattr_operations *ops;
+ int error = -EOPNOTSUPP;
+
+ lock_kernel();
+ ops = i->i_xop;
+ if (ops) {
+ if (flags & EA_CREATE) {
+ if (ops->create)
+ error = ops->create(i, name, value, size);
+ }
+ else if (flags & EA_REPLACE) {
+ if (ops->replace)
+ error = ops->replace(i, name, value, size);
+ }
+ else if (flags & EA_REMOVE) {
+ if (ops->remove)
+ error = ops->remove(i, name);
+ }
+ else if (ops->set)
+ error = ops->set(i, name, value, size);
+ }
+ unlock_kernel();
+ return error;
+}
+
+asmlinkage long
+sys_setxattr(char *path, char *name, void *value, size_t size, int flags)
+{
+ struct nameidata nd;
+ int error;
+
+ error = (flags & EA_NOFOLLOW)?
+ user_path_walk_link(path, &nd):
+ user_path_walk(path, &nd);
+ if (error)
+ return error;
+ error = setxattr(nd.dentry->d_inode, name, value, size, flags);
+ path_release(&nd);
+ return error;
+}
+
+asmlinkage long
+sys_fsetxattr(int fd, char *name, void *value, size_t size, int flags)
+{
+ struct file *f;
+ int error = -EBADF;
+
+ f = fget(fd);
+ if (!f)
+ return error;
+ error = setxattr(f->f_dentry->d_inode, name, value, size, flags);
+ fput(f);
+ return error;
+}
+
+
+/*
+ * Extended attribute GET operations
+ */
+static long
+getxattr(struct inode *i, char *name, void *value, size_t size, int flags)
+{
+ struct xattr_operations *ops;
+ int error = -EOPNOTSUPP;
+
+ lock_kernel();
+ ops = i->i_xop;
+ if (ops) {
+ if (flags & EA_SIZEONLY) {
+ if (ops->getsize)
+ error = ops->getsize(i, name);
+ }
+ else if (ops->get)
+ error = ops->get(i, name, value, size);
+ }
+ unlock_kernel();
+ return error;
+}
+
+asmlinkage long
+sys_getxattr(char *path, char *name, void *value, size_t size, int flags)
+{
+ struct nameidata nd;
+ int error;
+
+ error = (flags & EA_NOFOLLOW)?
+ user_path_walk_link(path, &nd):
+ user_path_walk(path, &nd);
+ if (error)
+ return error;
+ error = getxattr(nd.dentry->d_inode, name, value, size, flags);
+ path_release(&nd);
+ return error;
+}
+
+asmlinkage long
+sys_fgetxattr(int fd, char *name, void *value, size_t size, int flags)
+{
+ struct file *f;
+ int error = -EBADF;
+
+ f = fget(fd);
+ if (!f)
+ return error;
+ error = getxattr(f->f_dentry->d_inode, name, value, size, flags);
+ fput(f);
+ return error;
+}
+
+
+/*
+ * Extended attribute LIST operations
+ */
+static long
+listxattr(struct inode *i, char *name, void *value, size_t size, int flags)
+{
+ struct xattr_operations *ops;
+ int error = -EOPNOTSUPP;
+
+ lock_kernel();
+ ops = i->i_xop;
+ if (ops) {
+ if (flags & EA_SIZEONLY) {
+ if (ops->listsize)
+ error = ops->listsize(i, name);
+ }
+ else if (ops->list)
+ error = ops->list(i, name, value, size);
+ }
+ unlock_kernel();
+ return error;
+}
+
+asmlinkage long
+sys_listxattr(char *path, char *name, void *value, size_t size, int flags)
+{
+ struct nameidata nd;
+ int error;
+
+ error = (flags & EA_NOFOLLOW)?
+ user_path_walk_link(path, &nd):
+ user_path_walk(path, &nd);
+ if (error)
+ return error;
+ error = listxattr(nd.dentry->d_inode, name, value, size, flags);
+ path_release(&nd);
+ return error;
+}
+
+asmlinkage long
+sys_flistxattr(int fd, char *name, void *value, size_t size, int flags)
+{
+ struct file *f;
+ int error = -EBADF;
+
+ f = fget(fd);
+ if (!f)
+ return error;
+ error = listxattr(f->f_dentry->d_inode, name, value, size, flags);
+ fput(f);
+ return error;
+}
diff -Naur 2.4.14-pristine/fs/inode.c 2.4.14-al/fs/inode.c
--- 2.4.14-pristine/fs/inode.c Sat Sep 29 11:03:48 2001
+++ 2.4.14-al/fs/inode.c Tue Nov 13 16:11:15 2001
@@ -768,10 +768,12 @@
{
static struct address_space_operations empty_aops;
static struct inode_operations empty_iops;
+ static struct xattr_operations empty_xops;
static struct file_operations empty_fops;
memset(&inode->u, 0, sizeof(inode->u));
inode->i_sock = 0;
inode->i_op = &empty_iops;
+ inode->i_xop = &empty_xops;
inode->i_fop = &empty_fops;
inode->i_nlink = 1;
atomic_set(&inode->i_writecount, 0);
diff -Naur 2.4.14-pristine/include/asm-i386/unistd.h 2.4.14-al/include/asm-i386/unistd.h
--- 2.4.14-pristine/include/asm-i386/unistd.h Thu Oct 18 03:03:03 2001
+++ 2.4.14-al/include/asm-i386/unistd.h Tue Nov 13 15:53:21 2001
@@ -230,6 +230,12 @@
#define __NR_security 223 /* syscall for security modules */
#define __NR_gettid 224
#define __NR_readahead 225
+#define __NR_setxattr 226
+#define __NR_fsetxattr 227
+#define __NR_getxattr 228
+#define __NR_fgetxattr 229
+#define __NR_listxattr 230
+#define __NR_flistxattr 231

/* user-visible error numbers are in the range -1 - -124: see <asm-i386/errno.h> */

diff -Naur 2.4.14-pristine/include/linux/extattr.h 2.4.14-al/include/linux/extattr.h
--- 2.4.14-pristine/include/linux/extattr.h Thu Jan 1 10:00:00 1970
+++ 2.4.14-al/include/linux/extattr.h Tue Nov 13 15:43:08 2001
@@ -0,0 +1,18 @@
+/*
+ File: linux/extattr.h
+
+ Extended attributes handling.
+
+ Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>
+ Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>
+*/
+#ifndef _LINUX_EXTATTR_H
+#define _LINUX_EXTATTR_H
+
+#define EA_CREATE 0x0001 /* Set the value: fail if attr already exists */
+#define EA_REPLACE 0x0002 /* Set the value: fail if attr does not exist */
+#define EA_REMOVE 0x0004 /* Remove the named attribute entirely */
+#define EA_SIZEONLY 0x0008 /* Retrieve a buffer size don't write into it */
+#define EA_NOFOLLOW 0x0010 /* Don't follow symlinks when traversing path */
+
+#endif /* _LINUX_EXTATTR_H */
diff -Naur 2.4.14-pristine/include/linux/fs.h 2.4.14-al/include/linux/fs.h
--- 2.4.14-pristine/include/linux/fs.h Tue Nov 6 07:42:14 2001
+++ 2.4.14-al/include/linux/fs.h Tue Nov 13 15:30:39 2001
@@ -444,6 +444,7 @@
struct semaphore i_zombie;
struct inode_operations *i_op;
struct file_operations *i_fop; /* former ->i_op->default_file_ops */
+ struct xattr_operations *i_xop;
struct super_block *i_sb;
wait_queue_head_t i_wait;
struct file_lock *i_flock;
@@ -840,6 +841,17 @@
int (*revalidate) (struct dentry *);
int (*setattr) (struct dentry *, struct iattr *);
int (*getattr) (struct dentry *, struct iattr *);
+};
+
+struct xattr_operations {
+ int (*create) (struct inode *, char *, void *, size_t);
+ int (*replace) (struct inode *, char *, void *, size_t);
+ int (*remove) (struct inode *, char *);
+ int (*set) (struct inode *, char *, void *, size_t);
+ int (*get) (struct inode *, char *, void *, size_t);
+ int (*getsize) (struct inode *, char *);
+ int (*list) (struct inode *, char *, void *, size_t);
+ int (*listsize) (struct inode *, char *);
};

/*
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
\
 
 \ /
  Last update: 2005-03-22 13:13    [W:0.150 / U:0.236 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site