Al, folks,
Andreas and I have been looking at several different VFS mechanisms
for extended attributes, I've included the code for one below, and
we're keen to get a bit of feedback here as well.
We started off with the simplest mechanism, just passing everything
straight down into the filesystem. I then played around with some
ways of separating out the different operations and then passing off
to the filesystem that way (see patch) to give the interface a more
rigid definition. Andreas' original mechanism was alot like this,
except used NULLs in some field values instead of explicit flags to
distinguish similar operations - that's another approach.
Yet another way would be to have an ea_operations vector separate to
the inode_operations with an ea_operations pointer in struct inode,
enumerating each EA operation and doing away with the flags (in the
patch below) altogether.
Any suggestions/improvements? The patch below is very much a work
in progress - it may even compile.
many thanks.
-- Nathan
diff -Naur 2.4.14-pristine/arch/i386/kernel/entry.S 2.4.14-explicit/arch/i386/kernel/entry.S --- 2.4.14-pristine/arch/i386/kernel/entry.S Sat Nov 3 12:18:49 2001 +++ 2.4.14-explicit/arch/i386/kernel/entry.S Fri Nov 9 15:34:29 2001 @@ -622,6 +622,9 @@ .long SYMBOL_NAME(sys_ni_syscall) /* Reserved for Security */ .long SYMBOL_NAME(sys_gettid) .long SYMBOL_NAME(sys_readahead) /* 225 */ + .long SYMBOL_NAME(sys_extattr) + .long SYMBOL_NAME(sys_lextattr) + .long SYMBOL_NAME(sys_fextattr) .rept NR_syscalls-(.-sys_call_table)/4 .long SYMBOL_NAME(sys_ni_syscall) diff -Naur 2.4.14-pristine/fs/Makefile 2.4.14-explicit/fs/Makefile --- 2.4.14-pristine/fs/Makefile Tue Nov 6 08:40:59 2001 +++ 2.4.14-explicit/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-explicit/fs/extattr.c --- 2.4.14-pristine/fs/extattr.c Thu Jan 1 10:00:00 1970 +++ 2.4.14-explicit/fs/extattr.c Mon Nov 12 11:24:11 2001 @@ -0,0 +1,101 @@ +/* + 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> + +static long +extattr_inode(struct inode *i, int cmd, char *name, void *value, size_t size) +{ + int error = -EOPNOTSUPP, flags = EA_FLAG_USER; + + lock_kernel(); + switch (cmd) { + case EA_SET: + case EA_CREATE: + case EA_REPLACE: + case EA_REMOVE: + if (!i->i_op->setxattr) + break; + if (cmd == EA_CREATE) + flags |= EA_FLAG_CREATE; + else if (cmd == EA_REPLACE) + flags |= EA_FLAG_REPLACE; + else if (cmd == EA_REMOVE) + flags |= EA_FLAG_REMOVE; + error = i->i_op->setxattr(i, name, value, size, flags); + break; + + case EA_GETSIZE: + flags |= EA_FLAG_SZONLY; + case EA_GET: + if (!i->i_op->getxattr) + break; + error = i->i_op->getxattr(i, name, value, size, flags); + break; + + case EA_LISTSIZE: + flags |= EA_FLAG_SZONLY; + case EA_LIST: + if (!i->i_op->listxattr) + break; + error = i->i_op->listxattr(i, name, value, size, flags); + break; + + default: + error = -EINVAL; + } + unlock_kernel(); + return error; +} + +asmlinkage long +sys_extattr(char *path, int cmd, char *name, void *value, size_t size) +{ + struct nameidata nd; + int error; + + error = user_path_walk(path, &nd); + if (error) + return error; + error = extattr_inode(nd.dentry->d_inode, cmd, name, value, size); + path_release(&nd); + return error; +} + +asmlinkage long +sys_lextattr(char *path, int cmd, char *name, void *value, size_t size) +{ + struct nameidata nd; + int error; + + error = user_path_walk_link(path, &nd); + if (error) + return error; + error = extattr_inode(nd.dentry->d_inode, cmd, name, value, size); + path_release(&nd); + return error; +} + +asmlinkage long +sys_fextattr(int fd, int cmd, char *name, void *value, size_t size) +{ + struct file *f; + int error = -EBADF; + + f = fget(fd); + if (!f) + return error; + error = extattr_inode(f->f_dentry->d_inode, cmd, name, value, size); + fput(f); + return error; +} diff -Naur 2.4.14-pristine/include/asm-i386/unistd.h 2.4.14-explicit/include/asm-i386/unistd.h --- 2.4.14-pristine/include/asm-i386/unistd.h Thu Oct 18 03:03:03 2001 +++ 2.4.14-explicit/include/asm-i386/unistd.h Fri Nov 9 15:37:08 2001 @@ -230,6 +230,9 @@ #define __NR_security 223 /* syscall for security modules */ #define __NR_gettid 224 #define __NR_readahead 225 +#define __NR_extattr 226 +#define __NR_lextattr 227 +#define __NR_fextattr 228 /* 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-explicit/include/linux/extattr.h --- 2.4.14-pristine/include/linux/extattr.h Thu Jan 1 10:00:00 1970 +++ 2.4.14-explicit/include/linux/extattr.h Mon Nov 12 11:24:01 2001 @@ -0,0 +1,30 @@ +/* + 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 + +/* Operations */ +#define EA_SET 1 /* set the value, create attr where necessary */ +#define EA_CREATE 2 /* set the value, fail if attr already exists */ +#define EA_REPLACE 3 /* set the value, fail if attr does not exist */ +#define EA_REMOVE 4 /* remove the named attribute entirely */ +#define EA_GET 5 /* get the value for named attribute */ +#define EA_GETSIZE 6 /* size of value for named attribute */ +#define EA_LIST 7 /* get the list of attribute names */ +#define EA_LISTSIZE 8 /* size of list of attribute names */ + +#ifdef __KERNEL__ +#define EA_FLAG_USER 0x0001 +#define EA_FLAG_SZONLY 0x0002 +#define EA_FLAG_CREATE 0x0004 +#define EA_FLAG_REPLACE 0x0008 +#define EA_FLAG_REMOVE 0x0010 +#endif + +#endif /* _LINUX_EXTATTR_H */ diff -Naur 2.4.14-pristine/include/linux/fs.h 2.4.14-explicit/include/linux/fs.h --- 2.4.14-pristine/include/linux/fs.h Tue Nov 6 07:42:14 2001 +++ 2.4.14-explicit/include/linux/fs.h Sat Nov 10 14:10:39 2001 @@ -840,6 +840,9 @@ int (*revalidate) (struct dentry *); int (*setattr) (struct dentry *, struct iattr *); int (*getattr) (struct dentry *, struct iattr *); + int (*setxattr) (struct inode *, char *, void *, size_t, int); + int (*getxattr) (struct inode *, char *, void *, size_t, int); + int (*listxattr) (struct inode *, char *, void *, size_t, int); }; /* - 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/