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Commit 6f8880d8 authored by David Howells's avatar David Howells
Browse files

afs: Implement @sys substitution handling 



Implement the AFS feature by which @sys at the end of a pathname component
may be substituted for one of a list of values, typically naming the
operating system.  Up to 16 alternatives may be specified and these are
tried in turn until one works.  Each network namespace has[*] a separate
independent list.

Upon creation of a new network namespace, the list of values is
initialised[*] to a single OpenAFS-compatible string representing arch type
plus "_linux26".  For example, on x86_64, the sysname is "amd64_linux26".

[*] Or will, once network namespace support is finalised in kAFS.

The list may be set by:

	# for i in foo bar linux-x86_64; do echo $i; done >/proc/fs/afs/sysname

for which separate writes to the same fd are amalgamated and applied on
close.  The LF character may be used as a separator to specify multiple
items in the same write() call.

The list may be cleared by:

	# echo >/proc/fs/afs/sysname

and read by:

	# cat /proc/fs/afs/sysname
	foo
	bar
	linux-x86_64

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
parent 5cf9dd55

Documentation/filesystems/afs.txt

+27 −1
Original line number Diff line number Diff line
@@ -11,7 +11,7 @@ Contents: 
 - Proc filesystem.

 - The cell database.

 - Security.

 - Examples.

 - The @sys substitution.





========
@@ -230,3 +230,29 @@ If a file is opened with a particular key and then the file descriptor is 
passed to a process that doesn't have that key (perhaps over an AF_UNIX

socket), then the operations on the file will be made with key that was used to

open the file.





=====================

THE @SYS SUBSTITUTION

=====================



The list of up to 16 @sys substitutions for the current network namespace can

be configured by writing a list to /proc/fs/afs/sysname:



	[root@andromeda ~]# echo foo amd64_linux_26 >/proc/fs/afs/sysname



or cleared entirely by writing an empty list:



	[root@andromeda ~]# echo >/proc/fs/afs/sysname



The current list for current network namespace can be retrieved by:



	[root@andromeda ~]# cat /proc/fs/afs/sysname

	foo

	amd64_linux_26



When @sys is being substituted for, each element of the list is tried in the

order given.



By default, the list will contain one item that conforms to the pattern

"<arch>_linux_26", amd64 being the name for x86_64.

fs/afs/dir.c

+63 −0
Original line number Diff line number Diff line
@@ -766,6 +766,62 @@ static struct inode *afs_try_auto_mntpt(struct dentry *dentry, struct inode *dir 
	return ERR_PTR(ret);

}



/*

 * Look up an entry in a directory with @sys substitution.

 */

static struct dentry *afs_lookup_atsys(struct inode *dir, struct dentry *dentry,

				       struct key *key)

{

	struct afs_sysnames *subs;

	struct afs_net *net = afs_i2net(dir);

	struct dentry *ret;

	char *buf, *p, *name;

	int len, i;



	_enter("");



	ret = ERR_PTR(-ENOMEM);

	p = buf = kmalloc(AFSNAMEMAX, GFP_KERNEL);

	if (!buf)

		goto out_p;

	if (dentry->d_name.len > 4) {

		memcpy(p, dentry->d_name.name, dentry->d_name.len - 4);

		p += dentry->d_name.len - 4;

	}



	/* There is an ordered list of substitutes that we have to try. */

	read_lock(&net->sysnames_lock);

	subs = net->sysnames;

	refcount_inc(&subs->usage);

	read_unlock(&net->sysnames_lock);



	for (i = 0; i < subs->nr; i++) {

		name = subs->subs[i];

		len = dentry->d_name.len - 4 + strlen(name);

		if (len >= AFSNAMEMAX) {

			ret = ERR_PTR(-ENAMETOOLONG);

			goto out_s;

		}



		strcpy(p, name);

		ret = lookup_one_len(buf, dentry->d_parent, len);

		if (IS_ERR(ret) || d_is_positive(ret))

			goto out_s;

		dput(ret);

	}



	/* We don't want to d_add() the @sys dentry here as we don't want to

	 * the cached dentry to hide changes to the sysnames list.

	 */

	ret = NULL;

out_s:

	afs_put_sysnames(subs);

	kfree(buf);

out_p:

	key_put(key);

	return ret;

}



/*

 * look up an entry in a directory

 */
@@ -805,6 +861,13 @@ static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry, 
		return ERR_PTR(ret);

	}



	if (dentry->d_name.len >= 4 &&

	    dentry->d_name.name[dentry->d_name.len - 4] == '@' &&

	    dentry->d_name.name[dentry->d_name.len - 3] == 's' &&

	    dentry->d_name.name[dentry->d_name.len - 2] == 'y' &&

	    dentry->d_name.name[dentry->d_name.len - 1] == 's')

		return afs_lookup_atsys(dir, dentry, key);



	inode = afs_do_lookup(dir, dentry, key);

	if (IS_ERR(inode)) {

		ret = PTR_ERR(inode);

fs/afs/internal.h

+16 −0
Original line number Diff line number Diff line
@@ -198,6 +198,18 @@ static inline struct afs_super_info *AFS_FS_S(struct super_block *sb) 


extern struct file_system_type afs_fs_type;



/*

 * Set of substitutes for @sys.

 */

struct afs_sysnames {

#define AFS_NR_SYSNAME 16

	char			*subs[AFS_NR_SYSNAME];

	refcount_t		usage;

	unsigned short		nr;

	short			error;

	char			blank[1];

};



/*

 * AFS network namespace record.

 */
@@ -246,8 +258,11 @@ struct afs_net { 


	/* Misc */

	struct proc_dir_entry	*proc_afs;		/* /proc/net/afs directory */

	struct afs_sysnames	*sysnames;

	rwlock_t		sysnames_lock;

};



extern const char afs_init_sysname[];

extern struct afs_net __afs_net;// Dummy AFS network namespace; TODO: replace with real netns



enum afs_cell_state {
@@ -789,6 +804,7 @@ extern int __net_init afs_proc_init(struct afs_net *); 
extern void __net_exit afs_proc_cleanup(struct afs_net *);

extern int afs_proc_cell_setup(struct afs_net *, struct afs_cell *);

extern void afs_proc_cell_remove(struct afs_net *, struct afs_cell *);

extern void afs_put_sysnames(struct afs_sysnames *);



/*

 * rotate.c

fs/afs/main.c

+44 −0
Original line number Diff line number Diff line
@@ -34,11 +34,42 @@ MODULE_PARM_DESC(rootcell, "root AFS cell name and VL server IP addr list"); 
struct workqueue_struct *afs_wq;

struct afs_net __afs_net;



#if defined(CONFIG_ALPHA)

const char afs_init_sysname[] = "alpha_linux26";

#elif defined(CONFIG_X86_64)

const char afs_init_sysname[] = "amd64_linux26";

#elif defined(CONFIG_ARM)

const char afs_init_sysname[] = "arm_linux26";

#elif defined(CONFIG_ARM64)

const char afs_init_sysname[] = "aarch64_linux26";

#elif defined(CONFIG_X86_32)

const char afs_init_sysname[] = "i386_linux26";

#elif defined(CONFIG_IA64)

const char afs_init_sysname[] = "ia64_linux26";

#elif defined(CONFIG_PPC64)

const char afs_init_sysname[] = "ppc64_linux26";

#elif defined(CONFIG_PPC32)

const char afs_init_sysname[] = "ppc_linux26";

#elif defined(CONFIG_S390)

#ifdef CONFIG_64BIT

const char afs_init_sysname[] = "s390x_linux26";

#else

const char afs_init_sysname[] = "s390_linux26";

#endif

#elif defined(CONFIG_SPARC64)

const char afs_init_sysname[] = "sparc64_linux26";

#elif defined(CONFIG_SPARC32)

const char afs_init_sysname[] = "sparc_linux26";

#else

const char afs_init_sysname[] = "unknown_linux26";

#endif



/*

 * Initialise an AFS network namespace record.

 */

static int __net_init afs_net_init(struct afs_net *net)

{

	struct afs_sysnames *sysnames;

	int ret;



	net->live = true;
@@ -67,6 +98,16 @@ static int __net_init afs_net_init(struct afs_net *net) 
	INIT_WORK(&net->fs_manager, afs_manage_servers);

	timer_setup(&net->fs_timer, afs_servers_timer, 0);



	ret = -ENOMEM;

	sysnames = kzalloc(sizeof(*sysnames), GFP_KERNEL);

	if (!sysnames)

		goto error_sysnames;

	sysnames->subs[0] = (char *)&afs_init_sysname;

	sysnames->nr = 1;

	refcount_set(&sysnames->usage, 1);

	net->sysnames = sysnames;

	rwlock_init(&net->sysnames_lock);



	/* Register the /proc stuff */

	ret = afs_proc_init(net);

	if (ret < 0)
@@ -92,6 +133,8 @@ static int __net_init afs_net_init(struct afs_net *net) 
	net->live = false;

	afs_proc_cleanup(net);

error_proc:

	afs_put_sysnames(net->sysnames);

error_sysnames:

	net->live = false;

	return ret;

}
@@ -106,6 +149,7 @@ static void __net_exit afs_net_exit(struct afs_net *net) 
	afs_purge_servers(net);

	afs_close_socket(net);

	afs_proc_cleanup(net);

	afs_put_sysnames(net->sysnames);

}



/*

fs/afs/proc.c

+230 −1
Original line number Diff line number Diff line
@@ -126,6 +126,32 @@ static const struct file_operations afs_proc_servers_fops = { 
	.release	= seq_release,

};



static int afs_proc_sysname_open(struct inode *inode, struct file *file);

static int afs_proc_sysname_release(struct inode *inode, struct file *file);

static void *afs_proc_sysname_start(struct seq_file *p, loff_t *pos);

static void *afs_proc_sysname_next(struct seq_file *p, void *v,

					loff_t *pos);

static void afs_proc_sysname_stop(struct seq_file *p, void *v);

static int afs_proc_sysname_show(struct seq_file *m, void *v);

static ssize_t afs_proc_sysname_write(struct file *file,

				      const char __user *buf,

				      size_t size, loff_t *_pos);



static const struct seq_operations afs_proc_sysname_ops = {

	.start	= afs_proc_sysname_start,

	.next	= afs_proc_sysname_next,

	.stop	= afs_proc_sysname_stop,

	.show	= afs_proc_sysname_show,

};



static const struct file_operations afs_proc_sysname_fops = {

	.open		= afs_proc_sysname_open,

	.read		= seq_read,

	.llseek		= seq_lseek,

	.release	= afs_proc_sysname_release,

	.write		= afs_proc_sysname_write,

};



/*

 * initialise the /proc/fs/afs/ directory

 */
@@ -139,7 +165,8 @@ int afs_proc_init(struct afs_net *net) 


	if (!proc_create("cells", 0644, net->proc_afs, &afs_proc_cells_fops) ||

	    !proc_create("rootcell", 0644, net->proc_afs, &afs_proc_rootcell_fops) ||

	    !proc_create("servers", 0644, net->proc_afs, &afs_proc_servers_fops))

	    !proc_create("servers", 0644, net->proc_afs, &afs_proc_servers_fops) ||

	    !proc_create("sysname", 0644, net->proc_afs, &afs_proc_sysname_fops))

		goto error_tree;



	_leave(" = 0");
@@ -330,6 +357,12 @@ static ssize_t afs_proc_rootcell_write(struct file *file, 
	if (IS_ERR(kbuf))

		return PTR_ERR(kbuf);



	ret = -EINVAL;

	if (kbuf[0] == '.')

		goto out;

	if (memchr(kbuf, '/', size))

		goto out;



	/* trim to first NL */

	s = memchr(kbuf, '\n', size);

	if (s)
@@ -342,6 +375,7 @@ static ssize_t afs_proc_rootcell_write(struct file *file, 
	if (ret >= 0)

		ret = size;	/* consume everything, always */



out:

	kfree(kbuf);

	_leave(" = %d", ret);

	return ret;
@@ -635,3 +669,198 @@ static int afs_proc_servers_show(struct seq_file *m, void *v) 
		   &alist->addrs[alist->index].transport);

	return 0;

}



void afs_put_sysnames(struct afs_sysnames *sysnames)

{

	int i;



	if (sysnames && refcount_dec_and_test(&sysnames->usage)) {

		for (i = 0; i < sysnames->nr; i++)

			if (sysnames->subs[i] != afs_init_sysname &&

			    sysnames->subs[i] != sysnames->blank)

				kfree(sysnames->subs[i]);

	}

}



/*

 * Handle opening of /proc/fs/afs/sysname.  If it is opened for writing, we

 * assume the caller wants to change the substitution list and we allocate a

 * buffer to hold the list.

 */

static int afs_proc_sysname_open(struct inode *inode, struct file *file)

{

	struct afs_sysnames *sysnames;

	struct seq_file *m;

	int ret;



	ret = seq_open(file, &afs_proc_sysname_ops);

	if (ret < 0)

		return ret;



	if (file->f_mode & FMODE_WRITE) {

		sysnames = kzalloc(sizeof(*sysnames), GFP_KERNEL);

		if (!sysnames) {

			seq_release(inode, file);

			return -ENOMEM;

		}



		refcount_set(&sysnames->usage, 1);

		m = file->private_data;

		m->private = sysnames;

	}



	return 0;

}



/*

 * Handle writes to /proc/fs/afs/sysname to set the @sys substitution.

 */

static ssize_t afs_proc_sysname_write(struct file *file,

				      const char __user *buf,

				      size_t size, loff_t *_pos)

{

	struct afs_sysnames *sysnames;

	struct seq_file *m = file->private_data;

	char *kbuf = NULL, *s, *p, *sub;

	int ret, len;



	sysnames = m->private;

	if (!sysnames)

		return -EINVAL;

	if (sysnames->error)

		return sysnames->error;



	if (size >= PAGE_SIZE - 1) {

		sysnames->error = -EINVAL;

		return -EINVAL;

	}

	if (size == 0)

		return 0;



	kbuf = memdup_user_nul(buf, size);

	if (IS_ERR(kbuf))

		return PTR_ERR(kbuf);



	inode_lock(file_inode(file));



	p = kbuf;

	while ((s = strsep(&p, " \t\n"))) {

		len = strlen(s);

		if (len == 0)

			continue;

		ret = -ENAMETOOLONG;

		if (len >= AFSNAMEMAX)

			goto error;



		if (len >= 4 &&

		    s[len - 4] == '@' &&

		    s[len - 3] == 's' &&

		    s[len - 2] == 'y' &&

		    s[len - 1] == 's')

			/* Protect against recursion */

			goto invalid;



		if (s[0] == '.' &&

		    (len < 2 || (len == 2 && s[1] == '.')))

			goto invalid;



		if (memchr(s, '/', len))

			goto invalid;



		ret = -EFBIG;

		if (sysnames->nr >= AFS_NR_SYSNAME)

			goto out;



		if (strcmp(s, afs_init_sysname) == 0) {

			sub = (char *)afs_init_sysname;

		} else {

			ret = -ENOMEM;

			sub = kmemdup(s, len + 1, GFP_KERNEL);

			if (!sub)

				goto out;

		}



		sysnames->subs[sysnames->nr] = sub;

		sysnames->nr++;

	}



	ret = size;	/* consume everything, always */

out:

	inode_unlock(file_inode(file));

	kfree(kbuf);

	return ret;



invalid:

	ret = -EINVAL;

error:

	sysnames->error = ret;

	goto out;

}



static int afs_proc_sysname_release(struct inode *inode, struct file *file)

{

	struct afs_sysnames *sysnames, *kill = NULL;

	struct seq_file *m = file->private_data;

	struct afs_net *net = afs_seq2net(m);



	sysnames = m->private;

	if (sysnames) {

		if (!sysnames->error) {

			kill = sysnames;

			if (sysnames->nr == 0) {

				sysnames->subs[0] = sysnames->blank;

				sysnames->nr++;

			}

			write_lock(&net->sysnames_lock);

			kill = net->sysnames;

			net->sysnames = sysnames;

			write_unlock(&net->sysnames_lock);

		}

		afs_put_sysnames(kill);

	}



	return seq_release(inode, file);

}



static void *afs_proc_sysname_start(struct seq_file *m, loff_t *pos)

	__acquires(&net->sysnames_lock)

{

	struct afs_net *net = afs_seq2net(m);

	struct afs_sysnames *names = net->sysnames;



	read_lock(&net->sysnames_lock);



	if (*pos >= names->nr)

		return NULL;

	return (void *)(unsigned long)(*pos + 1);

}



static void *afs_proc_sysname_next(struct seq_file *m, void *v, loff_t *pos)

{

	struct afs_net *net = afs_seq2net(m);

	struct afs_sysnames *names = net->sysnames;



	*pos += 1;

	if (*pos >= names->nr)

		return NULL;

	return (void *)(unsigned long)(*pos + 1);

}



static void afs_proc_sysname_stop(struct seq_file *m, void *v)

	__releases(&net->sysnames_lock)

{

	struct afs_net *net = afs_seq2net(m);



	read_unlock(&net->sysnames_lock);

}



static int afs_proc_sysname_show(struct seq_file *m, void *v)

{

	struct afs_net *net = afs_seq2net(m);

	struct afs_sysnames *sysnames = net->sysnames;

	unsigned int i = (unsigned long)v - 1;



	if (i < sysnames->nr)

		seq_printf(m, "%s\n", sysnames->subs[i]);

	return 0;

}