[PATCH 1/3] NFS: Use kernel DNS resolver [ver #2]

[PATCH 1/3] NFS: Use kernel DNS resolver [ver #2]

[David Howells]

From: Bryan Schumaker <bjschuma-HgOvQuBEEgTQT0dZR+AlfA@public.gmane.org>

Use the kernel DNS resolver to translate hostnames to IP addresses.  Create a
new config option to choose between the legacy DNS resolver and the new
resolver.

Signed-off-by: Bryan Schumaker <bjschuma-HgOvQuBEEgTQT0dZR+AlfA@public.gmane.org>
Acked-by: Trond Myklebust <Trond.Myklebust-HgOvQuBEEgTQT0dZR+AlfA@public.gmane.org>
Signed-off-by: David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---

 fs/nfs/Kconfig       |   16 ++++++++++++++++
 fs/nfs/dns_resolve.c |   24 ++++++++++++++++++++++++
 fs/nfs/dns_resolve.h |   12 ++++++++++++
 3 files changed, 52 insertions(+), 0 deletions(-)

diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig
index cc1bb33..c5bbdca 100644
--- a/fs/nfs/Kconfig
+++ b/fs/nfs/Kconfig
@@ -100,3 +100,19 @@ config NFS_FSCACHE
 	help
 	  Say Y here if you want NFS data to be cached locally on disc through
 	  the general filesystem cache manager
+
+config NFS_USE_LEGACY_DNS
+	bool "Use the legacy NFS DNS resolver"
+	depends on NFS_V4
+	help
+	  The kernel now provides a method for translating a host name into an
+	  IP address.  Select Y here if you would rather use your own DNS
+	  resolver script.
+
+	  If unsure, say N
+
+config NFS_USE_KERNEL_DNS
+	bool
+	depends on NFS_V4 && !NFS_USE_LEGACY_DNS
+	select DNS_RESOLVER
+	default y
diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
index 76fd235..dba50a5 100644
--- a/fs/nfs/dns_resolve.c
+++ b/fs/nfs/dns_resolve.c
@@ -6,6 +6,29 @@
  * Resolves DNS hostnames into valid ip addresses
  */
 
+#ifdef CONFIG_NFS_USE_KERNEL_DNS
+
+#include <linux/sunrpc/clnt.h>
+#include <linux/dns_resolver.h>
+
+ssize_t nfs_dns_resolve_name(char *name, size_t namelen,
+		struct sockaddr *sa, size_t salen)
+{
+	ssize_t ret;
+	char *ip_addr = NULL;
+	int ip_len;
+
+	ip_len = dns_query(NULL, name, namelen, NULL, &ip_addr, NULL);
+	if (ip_len > 0)
+		ret = rpc_pton(ip_addr, ip_len, sa, salen);
+	else
+		ret = -ESRCH;
+	kfree(ip_addr);
+	return ret;
+}
+
+#else
+
 #include <linux/hash.h>
 #include <linux/string.h>
 #include <linux/kmod.h>
@@ -346,3 +369,4 @@ void nfs_dns_resolver_destroy(void)
 	nfs_cache_unregister(&nfs_dns_resolve);
 }
 
+#endif
diff --git a/fs/nfs/dns_resolve.h b/fs/nfs/dns_resolve.h
index a3f0938..199bb55 100644
--- a/fs/nfs/dns_resolve.h
+++ b/fs/nfs/dns_resolve.h
@@ -6,8 +6,20 @@
 
 #define NFS_DNS_HOSTNAME_MAXLEN	(128)
 
+
+#ifdef CONFIG_NFS_USE_KERNEL_DNS
+static inline int nfs_dns_resolver_init(void)
+{
+	return 0;
+}
+
+static inline void nfs_dns_resolver_destroy(void)
+{}
+#else
 extern int nfs_dns_resolver_init(void);
 extern void nfs_dns_resolver_destroy(void);
+#endif
+
 extern ssize_t nfs_dns_resolve_name(char *name, size_t namelen,
 		struct sockaddr *sa, size_t salen);
 

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[PATCH 1/3] NFS: Use kernel DNS resolver [ver #2]

[David Howells]

From: Bryan Schumaker <bjschuma@netapp.com>

Use the kernel DNS resolver to translate hostnames to IP addresses.  Create a
new config option to choose between the legacy DNS resolver and the new
resolver.

Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/nfs/Kconfig       |   16 ++++++++++++++++
 fs/nfs/dns_resolve.c |   24 ++++++++++++++++++++++++
 fs/nfs/dns_resolve.h |   12 ++++++++++++
 3 files changed, 52 insertions(+), 0 deletions(-)

diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig
index cc1bb33..c5bbdca 100644
--- a/fs/nfs/Kconfig
+++ b/fs/nfs/Kconfig
@@ -100,3 +100,19 @@ config NFS_FSCACHE
 	help
 	  Say Y here if you want NFS data to be cached locally on disc through
 	  the general filesystem cache manager
+
+config NFS_USE_LEGACY_DNS
+	bool "Use the legacy NFS DNS resolver"
+	depends on NFS_V4
+	help
+	  The kernel now provides a method for translating a host name into an
+	  IP address.  Select Y here if you would rather use your own DNS
+	  resolver script.
+
+	  If unsure, say N
+
+config NFS_USE_KERNEL_DNS
+	bool
+	depends on NFS_V4 && !NFS_USE_LEGACY_DNS
+	select DNS_RESOLVER
+	default y
diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
index 76fd235..dba50a5 100644
--- a/fs/nfs/dns_resolve.c
+++ b/fs/nfs/dns_resolve.c
@@ -6,6 +6,29 @@
  * Resolves DNS hostnames into valid ip addresses
  */
 
+#ifdef CONFIG_NFS_USE_KERNEL_DNS
+
+#include <linux/sunrpc/clnt.h>
+#include <linux/dns_resolver.h>
+
+ssize_t nfs_dns_resolve_name(char *name, size_t namelen,
+		struct sockaddr *sa, size_t salen)
+{
+	ssize_t ret;
+	char *ip_addr = NULL;
+	int ip_len;
+
+	ip_len = dns_query(NULL, name, namelen, NULL, &ip_addr, NULL);
+	if (ip_len > 0)
+		ret = rpc_pton(ip_addr, ip_len, sa, salen);
+	else
+		ret = -ESRCH;
+	kfree(ip_addr);
+	return ret;
+}
+
+#else
+
 #include <linux/hash.h>
 #include <linux/string.h>
 #include <linux/kmod.h>
@@ -346,3 +369,4 @@ void nfs_dns_resolver_destroy(void)
 	nfs_cache_unregister(&nfs_dns_resolve);
 }
 
+#endif
diff --git a/fs/nfs/dns_resolve.h b/fs/nfs/dns_resolve.h
index a3f0938..199bb55 100644
--- a/fs/nfs/dns_resolve.h
+++ b/fs/nfs/dns_resolve.h
@@ -6,8 +6,20 @@
 
 #define NFS_DNS_HOSTNAME_MAXLEN	(128)
 
+
+#ifdef CONFIG_NFS_USE_KERNEL_DNS
+static inline int nfs_dns_resolver_init(void)
+{
+	return 0;
+}
+
+static inline void nfs_dns_resolver_destroy(void)
+{}
+#else
 extern int nfs_dns_resolver_init(void);
 extern void nfs_dns_resolver_destroy(void);
+#endif
+
 extern ssize_t nfs_dns_resolve_name(char *name, size_t namelen,
 		struct sockaddr *sa, size_t salen);
 

[PATCH 2/3] DNS: If the DNS server returns an error, allow that to be cached [ver #2]

[David Howells]

From: Wang Lei <wang840925-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>

If the DNS server returns an error, allow that to be cached in the DNS resolver
key in lieu of a value.  Userspace passes the desired error number as an option
in the payload:

	"#dnserror=<number>"

Userspace must map h_errno from the name resolution routines to an appropriate
Linux error before passing it up.  Something like the following mapping is
recommended:

	[HOST_NOT_FOUND]	= ENODATA,
	[TRY_AGAIN]		= EAGAIN,
	[NO_RECOVERY]		= ECONNREFUSED,
	[NO_DATA]		= ENODATA,

in lieu of Linux errors specifically for representing name service errors.  The
filesystem must map these errors appropropriately before passing them to
userspace.  AFS is made to map ENODATA and EAGAIN to EDESTADDRREQ for the
return to userspace; ECONNREFUSED is allowed to stand as is.

The error can be seen in /proc/keys as a negative number after the description
of the key.  Compare, for example, the following key entries:

2f97238c I--Q--     1  53s 3f010000     0     0 dns_resol afsdb:grand.centrall.org: -61
338bfbbe I--Q--     1  59m 3f010000     0     0 dns_resol afsdb:grand.central.org: 37


If the error option is supplied in the payload, the main part of the payload is
discarded.  The key should have an expiry time set by userspace.

Signed-off-by: Wang Lei <wang840925-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Signed-off-by: David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Acked-by: Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---

 fs/afs/cell.c                |    4 ++
 net/dns_resolver/dns_key.c   |   92 ++++++++++++++++++++++++++++++++++++++++--
 net/dns_resolver/dns_query.c |    5 ++
 3 files changed, 96 insertions(+), 5 deletions(-)

diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index ffea35c..d076588 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -73,6 +73,10 @@ static struct afs_cell *afs_cell_alloc(const char *name, char *vllist)
 	if (!vllist || strlen(vllist) < 7) {
 		ret = dns_query("afsdb", name, namelen, "ipv4", &dvllist, NULL);
 		if (ret < 0) {
+			if (ret == -ENODATA || ret == -EAGAIN || ret == -ENOKEY)
+				/* translate these errors into something
+				 * userspace might understand */
+				ret = -EDESTADDRREQ;
 			_leave(" = %d", ret);
 			return ERR_PTR(ret);
 		}
diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c
index 400a04d..739435a 100644
--- a/net/dns_resolver/dns_key.c
+++ b/net/dns_resolver/dns_key.c
@@ -29,6 +29,7 @@
 #include <linux/kernel.h>
 #include <linux/keyctl.h>
 #include <linux/err.h>
+#include <linux/seq_file.h>
 #include <keys/dns_resolver-type.h>
 #include <keys/user-type.h>
 #include "internal.h"
@@ -43,6 +44,8 @@ MODULE_PARM_DESC(debug, "DNS Resolver debugging mask");
 
 const struct cred *dns_resolver_cache;
 
+#define	DNS_ERRORNO_OPTION	"dnserror"
+
 /*
  * Instantiate a user defined key for dns_resolver.
  *
@@ -59,9 +62,10 @@ static int
 dns_resolver_instantiate(struct key *key, const void *_data, size_t datalen)
 {
 	struct user_key_payload *upayload;
+	unsigned long derrno;
 	int ret;
 	size_t result_len = 0;
-	const char *data = _data, *opt;
+	const char *data = _data, *end, *opt;
 
 	kenter("%%%d,%s,'%s',%zu",
 	       key->serial, key->description, data, datalen);
@@ -71,13 +75,77 @@ dns_resolver_instantiate(struct key *key, const void *_data, size_t datalen)
 	datalen--;
 
 	/* deal with any options embedded in the data */
+	end = data + datalen;
 	opt = memchr(data, '#', datalen);
 	if (!opt) {
-		kdebug("no options currently supported");
-		return -EINVAL;
+		/* no options: the entire data is the result */
+		kdebug("no options");
+		result_len = datalen;
+	} else {
+		const char *next_opt;
+
+		result_len = opt - data;
+		opt++;
+		kdebug("options: '%s'", opt);
+		do {
+			const char *eq;
+			int opt_len, opt_nlen, opt_vlen, tmp;
+
+			next_opt = memchr(opt, '#', end - opt) ?: end;
+			opt_len = next_opt - opt;
+			if (!opt_len) {
+				printk(KERN_WARNING
+				       "Empty option to dns_resolver key %d\n",
+				       key->serial);
+				return -EINVAL;
+			}
+
+			eq = memchr(opt, '=', opt_len) ?: end;
+			opt_nlen = eq - opt;
+			eq++;
+			opt_vlen = next_opt - eq; /* will be -1 if no value */
+
+			tmp = opt_vlen >= 0 ? opt_vlen : 0;
+			kdebug("option '%*.*s' val '%*.*s'",
+			       opt_nlen, opt_nlen, opt, tmp, tmp, eq);
+
+			/* see if it's an error number representing a DNS error
+			 * that's to be recorded as the result in this key */
+			if (opt_nlen == sizeof(DNS_ERRORNO_OPTION) - 1 &&
+			    memcmp(opt, DNS_ERRORNO_OPTION, opt_nlen) == 0) {
+				kdebug("dns error number option");
+				if (opt_vlen <= 0)
+					goto bad_option_value;
+
+				ret = strict_strtoul(eq, 10, &derrno);
+				if (ret < 0)
+					goto bad_option_value;
+
+				if (derrno < 1 || derrno > 511)
+					goto bad_option_value;
+
+				kdebug("dns error no. = %lu", derrno);
+				key->type_data.x[0] = -derrno;
+				continue;
+			}
+
+		bad_option_value:
+			printk(KERN_WARNING
+			       "Option '%*.*s' to dns_resolver key %d:"
+			       " bad/missing value\n",
+			       opt_nlen, opt_nlen, opt, key->serial);
+			return -EINVAL;
+		} while (opt = next_opt + 1, opt < end);
+	}
+
+	/* don't cache the result if we're caching an error saying there's no
+	 * result */
+	if (key->type_data.x[0]) {
+		kleave(" = 0 [h_error %ld]", key->type_data.x[0]);
+		return 0;
 	}
 
-	result_len = datalen;
+	kdebug("store result");
 	ret = key_payload_reserve(key, result_len);
 	if (ret < 0)
 		return -EINVAL;
@@ -135,13 +203,27 @@ no_match:
 	return ret;
 }
 
+/*
+ * Describe a DNS key
+ */
+static void dns_resolver_describe(const struct key *key, struct seq_file *m)
+{
+	int err = key->type_data.x[0];
+
+	seq_puts(m, key->description);
+	if (err)
+		seq_printf(m, ": %d", err);
+	else
+		seq_printf(m, ": %u", key->datalen);
+}
+
 struct key_type key_type_dns_resolver = {
 	.name		= "dns_resolver",
 	.instantiate	= dns_resolver_instantiate,
 	.match		= dns_resolver_match,
 	.revoke		= user_revoke,
 	.destroy	= user_destroy,
-	.describe	= user_describe,
+	.describe	= dns_resolver_describe,
 	.read		= user_read,
 };
 
diff --git a/net/dns_resolver/dns_query.c b/net/dns_resolver/dns_query.c
index 03d5255..c32be29 100644
--- a/net/dns_resolver/dns_query.c
+++ b/net/dns_resolver/dns_query.c
@@ -136,6 +136,11 @@ int dns_query(const char *type, const char *name, size_t namelen,
 	if (ret < 0)
 		goto put;
 
+	/* If the DNS server gave an error, return that to the caller */
+	ret = rkey->type_data.x[0];
+	if (ret)
+		goto put;
+
 	upayload = rcu_dereference_protected(rkey->payload.data,
 					     lockdep_is_held(&rkey->sem));
 	len = upayload->datalen;

[PATCH 2/3] DNS: If the DNS server returns an error, allow that to be cached [ver #2]

[David Howells]

From: Wang Lei <wang840925@gmail.com>

If the DNS server returns an error, allow that to be cached in the DNS resolver
key in lieu of a value.  Userspace passes the desired error number as an option
in the payload:

	"#dnserror=<number>"

Userspace must map h_errno from the name resolution routines to an appropriate
Linux error before passing it up.  Something like the following mapping is
recommended:

	[HOST_NOT_FOUND]	= ENODATA,
	[TRY_AGAIN]		= EAGAIN,
	[NO_RECOVERY]		= ECONNREFUSED,
	[NO_DATA]		= ENODATA,

in lieu of Linux errors specifically for representing name service errors.  The
filesystem must map these errors appropropriately before passing them to
userspace.  AFS is made to map ENODATA and EAGAIN to EDESTADDRREQ for the
return to userspace; ECONNREFUSED is allowed to stand as is.

The error can be seen in /proc/keys as a negative number after the description
of the key.  Compare, for example, the following key entries:

2f97238c I--Q--     1  53s 3f010000     0     0 dns_resol afsdb:grand.centrall.org: -61
338bfbbe I--Q--     1  59m 3f010000     0     0 dns_resol afsdb:grand.central.org: 37


If the error option is supplied in the payload, the main part of the payload is
discarded.  The key should have an expiry time set by userspace.

Signed-off-by: Wang Lei <wang840925@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
---

 fs/afs/cell.c                |    4 ++
 net/dns_resolver/dns_key.c   |   92 ++++++++++++++++++++++++++++++++++++++++--
 net/dns_resolver/dns_query.c |    5 ++
 3 files changed, 96 insertions(+), 5 deletions(-)

diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index ffea35c..d076588 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -73,6 +73,10 @@ static struct afs_cell *afs_cell_alloc(const char *name, char *vllist)
 	if (!vllist || strlen(vllist) < 7) {
 		ret = dns_query("afsdb", name, namelen, "ipv4", &dvllist, NULL);
 		if (ret < 0) {
+			if (ret == -ENODATA || ret == -EAGAIN || ret == -ENOKEY)
+				/* translate these errors into something
+				 * userspace might understand */
+				ret = -EDESTADDRREQ;
 			_leave(" = %d", ret);
 			return ERR_PTR(ret);
 		}
diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c
index 400a04d..739435a 100644
--- a/net/dns_resolver/dns_key.c
+++ b/net/dns_resolver/dns_key.c
@@ -29,6 +29,7 @@
 #include <linux/kernel.h>
 #include <linux/keyctl.h>
 #include <linux/err.h>
+#include <linux/seq_file.h>
 #include <keys/dns_resolver-type.h>
 #include <keys/user-type.h>
 #include "internal.h"
@@ -43,6 +44,8 @@ MODULE_PARM_DESC(debug, "DNS Resolver debugging mask");
 
 const struct cred *dns_resolver_cache;
 
+#define	DNS_ERRORNO_OPTION	"dnserror"
+
 /*
  * Instantiate a user defined key for dns_resolver.
  *
@@ -59,9 +62,10 @@ static int
 dns_resolver_instantiate(struct key *key, const void *_data, size_t datalen)
 {
 	struct user_key_payload *upayload;
+	unsigned long derrno;
 	int ret;
 	size_t result_len = 0;
-	const char *data = _data, *opt;
+	const char *data = _data, *end, *opt;
 
 	kenter("%%%d,%s,'%s',%zu",
 	       key->serial, key->description, data, datalen);
@@ -71,13 +75,77 @@ dns_resolver_instantiate(struct key *key, const void *_data, size_t datalen)
 	datalen--;
 
 	/* deal with any options embedded in the data */
+	end = data + datalen;
 	opt = memchr(data, '#', datalen);
 	if (!opt) {
-		kdebug("no options currently supported");
-		return -EINVAL;
+		/* no options: the entire data is the result */
+		kdebug("no options");
+		result_len = datalen;
+	} else {
+		const char *next_opt;
+
+		result_len = opt - data;
+		opt++;
+		kdebug("options: '%s'", opt);
+		do {
+			const char *eq;
+			int opt_len, opt_nlen, opt_vlen, tmp;
+
+			next_opt = memchr(opt, '#', end - opt) ?: end;
+			opt_len = next_opt - opt;
+			if (!opt_len) {
+				printk(KERN_WARNING
+				       "Empty option to dns_resolver key %d\n",
+				       key->serial);
+				return -EINVAL;
+			}
+
+			eq = memchr(opt, '=', opt_len) ?: end;
+			opt_nlen = eq - opt;
+			eq++;
+			opt_vlen = next_opt - eq; /* will be -1 if no value */
+
+			tmp = opt_vlen >= 0 ? opt_vlen : 0;
+			kdebug("option '%*.*s' val '%*.*s'",
+			       opt_nlen, opt_nlen, opt, tmp, tmp, eq);
+
+			/* see if it's an error number representing a DNS error
+			 * that's to be recorded as the result in this key */
+			if (opt_nlen == sizeof(DNS_ERRORNO_OPTION) - 1 &&
+			    memcmp(opt, DNS_ERRORNO_OPTION, opt_nlen) == 0) {
+				kdebug("dns error number option");
+				if (opt_vlen <= 0)
+					goto bad_option_value;
+
+				ret = strict_strtoul(eq, 10, &derrno);
+				if (ret < 0)
+					goto bad_option_value;
+
+				if (derrno < 1 || derrno > 511)
+					goto bad_option_value;
+
+				kdebug("dns error no. = %lu", derrno);
+				key->type_data.x[0] = -derrno;
+				continue;
+			}
+
+		bad_option_value:
+			printk(KERN_WARNING
+			       "Option '%*.*s' to dns_resolver key %d:"
+			       " bad/missing value\n",
+			       opt_nlen, opt_nlen, opt, key->serial);
+			return -EINVAL;
+		} while (opt = next_opt + 1, opt < end);
+	}
+
+	/* don't cache the result if we're caching an error saying there's no
+	 * result */
+	if (key->type_data.x[0]) {
+		kleave(" = 0 [h_error %ld]", key->type_data.x[0]);
+		return 0;
 	}
 
-	result_len = datalen;
+	kdebug("store result");
 	ret = key_payload_reserve(key, result_len);
 	if (ret < 0)
 		return -EINVAL;
@@ -135,13 +203,27 @@ no_match:
 	return ret;
 }
 
+/*
+ * Describe a DNS key
+ */
+static void dns_resolver_describe(const struct key *key, struct seq_file *m)
+{
+	int err = key->type_data.x[0];
+
+	seq_puts(m, key->description);
+	if (err)
+		seq_printf(m, ": %d", err);
+	else
+		seq_printf(m, ": %u", key->datalen);
+}
+
 struct key_type key_type_dns_resolver = {
 	.name		= "dns_resolver",
 	.instantiate	= dns_resolver_instantiate,
 	.match		= dns_resolver_match,
 	.revoke		= user_revoke,
 	.destroy	= user_destroy,
-	.describe	= user_describe,
+	.describe	= dns_resolver_describe,
 	.read		= user_read,
 };
 
diff --git a/net/dns_resolver/dns_query.c b/net/dns_resolver/dns_query.c
index 03d5255..c32be29 100644
--- a/net/dns_resolver/dns_query.c
+++ b/net/dns_resolver/dns_query.c
@@ -136,6 +136,11 @@ int dns_query(const char *type, const char *name, size_t namelen,
 	if (ret < 0)
 		goto put;
 
+	/* If the DNS server gave an error, return that to the caller */
+	ret = rkey->type_data.x[0];
+	if (ret)
+		goto put;
+
 	upayload = rcu_dereference_protected(rkey->payload.data,
 					     lockdep_is_held(&rkey->sem));
 	len = upayload->datalen;

Re: [PATCH 1/3] NFS: Use kernel DNS resolver [ver #2]

[Steve French]

Patches 1 - 3 of this series now in cifs-2.6.git

On Wed, Aug 11, 2010 at 3:37 AM, David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> From: Bryan Schumaker <bjschuma-HgOvQuBEEgTQT0dZR+AlfA@public.gmane.org>
>
> Use the kernel DNS resolver to translate hostnames to IP addresses.  Create a
> new config option to choose between the legacy DNS resolver and the new
> resolver.
>
> Signed-off-by: Bryan Schumaker <bjschuma-HgOvQuBEEgTQT0dZR+AlfA@public.gmane.org>
> Acked-by: Trond Myklebust <Trond.Myklebust-HgOvQuBEEgTQT0dZR+AlfA@public.gmane.org>
> Signed-off-by: David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> ---
>
>  fs/nfs/Kconfig       |   16 ++++++++++++++++
>  fs/nfs/dns_resolve.c |   24 ++++++++++++++++++++++++
>  fs/nfs/dns_resolve.h |   12 ++++++++++++
>  3 files changed, 52 insertions(+), 0 deletions(-)
>
> diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig
> index cc1bb33..c5bbdca 100644
> --- a/fs/nfs/Kconfig
> +++ b/fs/nfs/Kconfig
> @@ -100,3 +100,19 @@ config NFS_FSCACHE
>        help
>          Say Y here if you want NFS data to be cached locally on disc through
>          the general filesystem cache manager
> +
> +config NFS_USE_LEGACY_DNS
> +       bool "Use the legacy NFS DNS resolver"
> +       depends on NFS_V4
> +       help
> +         The kernel now provides a method for translating a host name into an
> +         IP address.  Select Y here if you would rather use your own DNS
> +         resolver script.
> +
> +         If unsure, say N
> +
> +config NFS_USE_KERNEL_DNS
> +       bool
> +       depends on NFS_V4 && !NFS_USE_LEGACY_DNS
> +       select DNS_RESOLVER
> +       default y
> diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
> index 76fd235..dba50a5 100644
> --- a/fs/nfs/dns_resolve.c
> +++ b/fs/nfs/dns_resolve.c
> @@ -6,6 +6,29 @@
>  * Resolves DNS hostnames into valid ip addresses
>  */
>
> +#ifdef CONFIG_NFS_USE_KERNEL_DNS
> +
> +#include <linux/sunrpc/clnt.h>
> +#include <linux/dns_resolver.h>
> +
> +ssize_t nfs_dns_resolve_name(char *name, size_t namelen,
> +               struct sockaddr *sa, size_t salen)
> +{
> +       ssize_t ret;
> +       char *ip_addr = NULL;
> +       int ip_len;
> +
> +       ip_len = dns_query(NULL, name, namelen, NULL, &ip_addr, NULL);
> +       if (ip_len > 0)
> +               ret = rpc_pton(ip_addr, ip_len, sa, salen);
> +       else
> +               ret = -ESRCH;
> +       kfree(ip_addr);
> +       return ret;
> +}
> +
> +#else
> +
>  #include <linux/hash.h>
>  #include <linux/string.h>
>  #include <linux/kmod.h>
> @@ -346,3 +369,4 @@ void nfs_dns_resolver_destroy(void)
>        nfs_cache_unregister(&nfs_dns_resolve);
>  }
>
> +#endif
> diff --git a/fs/nfs/dns_resolve.h b/fs/nfs/dns_resolve.h
> index a3f0938..199bb55 100644
> --- a/fs/nfs/dns_resolve.h
> +++ b/fs/nfs/dns_resolve.h
> @@ -6,8 +6,20 @@
>
>  #define NFS_DNS_HOSTNAME_MAXLEN        (128)
>
> +
> +#ifdef CONFIG_NFS_USE_KERNEL_DNS
> +static inline int nfs_dns_resolver_init(void)
> +{
> +       return 0;
> +}
> +
> +static inline void nfs_dns_resolver_destroy(void)
> +{}
> +#else
>  extern int nfs_dns_resolver_init(void);
>  extern void nfs_dns_resolver_destroy(void);
> +#endif
> +
>  extern ssize_t nfs_dns_resolve_name(char *name, size_t namelen,
>                struct sockaddr *sa, size_t salen);
>
>
>



-- 
Thanks,

Steve

Re: [PATCH 1/3] NFS: Use kernel DNS resolver [ver #2]

[Steve French]

Patches 1 - 3 of this series now in cifs-2.6.git

On Wed, Aug 11, 2010 at 3:37 AM, David Howells <dhowells@redhat.com> wr=
ote:
> From: Bryan Schumaker <bjschuma@netapp.com>
>
> Use the kernel DNS resolver to translate hostnames to IP addresses. =A0=
Create a
> new config option to choose between the legacy DNS resolver and the n=
ew
> resolver.
>
> Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
> Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
> Signed-off-by: David Howells <dhowells@redhat.com>
> ---
>
> =A0fs/nfs/Kconfig =A0 =A0 =A0 | =A0 16 ++++++++++++++++
> =A0fs/nfs/dns_resolve.c | =A0 24 ++++++++++++++++++++++++
> =A0fs/nfs/dns_resolve.h | =A0 12 ++++++++++++
> =A03 files changed, 52 insertions(+), 0 deletions(-)
>
> diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig
> index cc1bb33..c5bbdca 100644
> --- a/fs/nfs/Kconfig
> +++ b/fs/nfs/Kconfig
> @@ -100,3 +100,19 @@ config NFS_FSCACHE
> =A0 =A0 =A0 =A0help
> =A0 =A0 =A0 =A0 =A0Say Y here if you want NFS data to be cached local=
ly on disc through
> =A0 =A0 =A0 =A0 =A0the general filesystem cache manager
> +
> +config NFS_USE_LEGACY_DNS
> + =A0 =A0 =A0 bool "Use the legacy NFS DNS resolver"
> + =A0 =A0 =A0 depends on NFS_V4
> + =A0 =A0 =A0 help
> + =A0 =A0 =A0 =A0 The kernel now provides a method for translating a =
host name into an
> + =A0 =A0 =A0 =A0 IP address. =A0Select Y here if you would rather us=
e your own DNS
> + =A0 =A0 =A0 =A0 resolver script.
> +
> + =A0 =A0 =A0 =A0 If unsure, say N
> +
> +config NFS_USE_KERNEL_DNS
> + =A0 =A0 =A0 bool
> + =A0 =A0 =A0 depends on NFS_V4 && !NFS_USE_LEGACY_DNS
> + =A0 =A0 =A0 select DNS_RESOLVER
> + =A0 =A0 =A0 default y
> diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
> index 76fd235..dba50a5 100644
> --- a/fs/nfs/dns_resolve.c
> +++ b/fs/nfs/dns_resolve.c
> @@ -6,6 +6,29 @@
> =A0* Resolves DNS hostnames into valid ip addresses
> =A0*/
>
> +#ifdef CONFIG_NFS_USE_KERNEL_DNS
> +
> +#include <linux/sunrpc/clnt.h>
> +#include <linux/dns_resolver.h>
> +
> +ssize_t nfs_dns_resolve_name(char *name, size_t namelen,
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 struct sockaddr *sa, size_t salen)
> +{
> + =A0 =A0 =A0 ssize_t ret;
> + =A0 =A0 =A0 char *ip_addr =3D NULL;
> + =A0 =A0 =A0 int ip_len;
> +
> + =A0 =A0 =A0 ip_len =3D dns_query(NULL, name, namelen, NULL, &ip_add=
r, NULL);
> + =A0 =A0 =A0 if (ip_len > 0)
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 ret =3D rpc_pton(ip_addr, ip_len, sa, s=
alen);
> + =A0 =A0 =A0 else
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 ret =3D -ESRCH;
> + =A0 =A0 =A0 kfree(ip_addr);
> + =A0 =A0 =A0 return ret;
> +}
> +
> +#else
> +
> =A0#include <linux/hash.h>
> =A0#include <linux/string.h>
> =A0#include <linux/kmod.h>
> @@ -346,3 +369,4 @@ void nfs_dns_resolver_destroy(void)
> =A0 =A0 =A0 =A0nfs_cache_unregister(&nfs_dns_resolve);
> =A0}
>
> +#endif
> diff --git a/fs/nfs/dns_resolve.h b/fs/nfs/dns_resolve.h
> index a3f0938..199bb55 100644
> --- a/fs/nfs/dns_resolve.h
> +++ b/fs/nfs/dns_resolve.h
> @@ -6,8 +6,20 @@
>
> =A0#define NFS_DNS_HOSTNAME_MAXLEN =A0 =A0 =A0 =A0(128)
>
> +
> +#ifdef CONFIG_NFS_USE_KERNEL_DNS
> +static inline int nfs_dns_resolver_init(void)
> +{
> + =A0 =A0 =A0 return 0;
> +}
> +
> +static inline void nfs_dns_resolver_destroy(void)
> +{}
> +#else
> =A0extern int nfs_dns_resolver_init(void);
> =A0extern void nfs_dns_resolver_destroy(void);
> +#endif
> +
> =A0extern ssize_t nfs_dns_resolve_name(char *name, size_t namelen,
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0struct sockaddr *sa, size_t salen);
>
>
>



--=20
Thanks,

Steve

Re: [PATCH 1/3] NFS: Use kernel DNS resolver [ver #2]

[Steve French]

Patches 1 - 3 of this series now in cifs-2.6.git

On Wed, Aug 11, 2010 at 3:37 AM, David Howells <dhowells@redhat.com> wrote:
> From: Bryan Schumaker <bjschuma@netapp.com>
>
> Use the kernel DNS resolver to translate hostnames to IP addresses.  Create a
> new config option to choose between the legacy DNS resolver and the new
> resolver.
>
> Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
> Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
> Signed-off-by: David Howells <dhowells@redhat.com>
> ---
>
>  fs/nfs/Kconfig       |   16 ++++++++++++++++
>  fs/nfs/dns_resolve.c |   24 ++++++++++++++++++++++++
>  fs/nfs/dns_resolve.h |   12 ++++++++++++
>  3 files changed, 52 insertions(+), 0 deletions(-)
>
> diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig
> index cc1bb33..c5bbdca 100644
> --- a/fs/nfs/Kconfig
> +++ b/fs/nfs/Kconfig
> @@ -100,3 +100,19 @@ config NFS_FSCACHE
>        help
>          Say Y here if you want NFS data to be cached locally on disc through
>          the general filesystem cache manager
> +
> +config NFS_USE_LEGACY_DNS
> +       bool "Use the legacy NFS DNS resolver"
> +       depends on NFS_V4
> +       help
> +         The kernel now provides a method for translating a host name into an
> +         IP address.  Select Y here if you would rather use your own DNS
> +         resolver script.
> +
> +         If unsure, say N
> +
> +config NFS_USE_KERNEL_DNS
> +       bool
> +       depends on NFS_V4 && !NFS_USE_LEGACY_DNS
> +       select DNS_RESOLVER
> +       default y
> diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
> index 76fd235..dba50a5 100644
> --- a/fs/nfs/dns_resolve.c
> +++ b/fs/nfs/dns_resolve.c
> @@ -6,6 +6,29 @@
>  * Resolves DNS hostnames into valid ip addresses
>  */
>
> +#ifdef CONFIG_NFS_USE_KERNEL_DNS
> +
> +#include <linux/sunrpc/clnt.h>
> +#include <linux/dns_resolver.h>
> +
> +ssize_t nfs_dns_resolve_name(char *name, size_t namelen,
> +               struct sockaddr *sa, size_t salen)
> +{
> +       ssize_t ret;
> +       char *ip_addr = NULL;
> +       int ip_len;
> +
> +       ip_len = dns_query(NULL, name, namelen, NULL, &ip_addr, NULL);
> +       if (ip_len > 0)
> +               ret = rpc_pton(ip_addr, ip_len, sa, salen);
> +       else
> +               ret = -ESRCH;
> +       kfree(ip_addr);
> +       return ret;
> +}
> +
> +#else
> +
>  #include <linux/hash.h>
>  #include <linux/string.h>
>  #include <linux/kmod.h>
> @@ -346,3 +369,4 @@ void nfs_dns_resolver_destroy(void)
>        nfs_cache_unregister(&nfs_dns_resolve);
>  }
>
> +#endif
> diff --git a/fs/nfs/dns_resolve.h b/fs/nfs/dns_resolve.h
> index a3f0938..199bb55 100644
> --- a/fs/nfs/dns_resolve.h
> +++ b/fs/nfs/dns_resolve.h
> @@ -6,8 +6,20 @@
>
>  #define NFS_DNS_HOSTNAME_MAXLEN        (128)
>
> +
> +#ifdef CONFIG_NFS_USE_KERNEL_DNS
> +static inline int nfs_dns_resolver_init(void)
> +{
> +       return 0;
> +}
> +
> +static inline void nfs_dns_resolver_destroy(void)
> +{}
> +#else
>  extern int nfs_dns_resolver_init(void);
>  extern void nfs_dns_resolver_destroy(void);
> +#endif
> +
>  extern ssize_t nfs_dns_resolve_name(char *name, size_t namelen,
>                struct sockaddr *sa, size_t salen);
>
>
>



-- 
Thanks,

Steve

[PATCH 3/3] AFS: Implement an autocell mount capability [ver #2]

[David Howells]

From: wanglei <wang840925@gmail.com>

Implement the ability for the root directory of a mounted AFS filesystem to
accept lookups of arbitrary directory names, to interpet the names as the names
of cells, to look the cell names up in the DNS for AFSDB records and to mount
the root.cell volume of the nominated cell on the pseudo-directory created by
lookup.

This facility is requested by passing:

	-o autocell

to the mountpoint for which this is desired, usually the /afs mount.


To use this facility, a DNS upcall program is required for AFSDB records.  This
can be obtained from:

	http://people.redhat.com/~dhowells/afs/dns.afsdb.c

It should be compiled with -lresolv and -lkeyutils and installed as, say:

	/usr/sbin/dns.afsdb

Then the following line needs to be added to /sbin/request-key.conf:

	create	dns_resolver afsdb:*	*	/usr/sbin/dns.afsdb %k

This can be tested by mounting AFS, say:

	insmod dns_resolver.ko
	insmod af-rxrpc.ko
	insmod kafs.ko rootcell=grand.central.org
	mount -t afs "#grand.central.org:root.cell." /afs -o autocell

and doing:

	ls /afs/grand.central.org/

which should show:

	archive/  cvs/  doc/  local/  project/  service/  software/  user/  www/

if it works.

Signed-off-by: Wang Lei <wang840925@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/afs/cell.c     |   52 +++++++++++++++++++++++---------
 fs/afs/dir.c      |   47 ++++++++++++++++++++++++++++-
 fs/afs/inode.c    |   86 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/afs/internal.h |   11 ++++++-
 fs/afs/mntpt.c    |   78 ++++++++++++++++++++++++++++++++++--------------
 fs/afs/proc.c     |    2 +
 fs/afs/super.c    |   20 ++++++++++--
 7 files changed, 250 insertions(+), 46 deletions(-)

diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index d076588..0d5eead 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -31,21 +31,20 @@ static struct afs_cell *afs_cell_root;
  * allocate a cell record and fill in its name, VL server address list and
  * allocate an anonymous key
  */
-static struct afs_cell *afs_cell_alloc(const char *name, char *vllist)
+static struct afs_cell *afs_cell_alloc(const char *name, unsigned namelen,
+				       char *vllist)
 {
 	struct afs_cell *cell;
 	struct key *key;
-	size_t namelen;
 	char keyname[4 + AFS_MAXCELLNAME + 1], *cp, *dp, *next;
 	char  *dvllist = NULL, *_vllist = NULL;
 	char  delimiter = ':';
 	int ret;
 
-	_enter("%s,%s", name, vllist);
+	_enter("%*.*s,%s", namelen, namelen, name ?: "", vllist);
 
 	BUG_ON(!name); /* TODO: want to look up "this cell" in the cache */
 
-	namelen = strlen(name);
 	if (namelen > AFS_MAXCELLNAME) {
 		_leave(" = -ENAMETOOLONG");
 		return ERR_PTR(-ENAMETOOLONG);
@@ -142,26 +141,29 @@ error:
 }
 
 /*
- * create a cell record
- * - "name" is the name of the cell
- * - "vllist" is a colon separated list of IP addresses in "a.b.c.d" format
+ * afs_cell_crate() - create a cell record
+ * @name:	is the name of the cell.
+ * @namsesz:	is the strlen of the cell name.
+ * @vllist:	is a colon separated list of IP addresses in "a.b.c.d" format.
+ * @retref:	is T to return the cell reference when the cell exists.
  */
-struct afs_cell *afs_cell_create(const char *name, char *vllist)
+struct afs_cell *afs_cell_create(const char *name, unsigned namesz,
+				 char *vllist, bool retref)
 {
 	struct afs_cell *cell;
 	int ret;
 
-	_enter("%s,%s", name, vllist);
+	_enter("%*.*s,%s", namesz, namesz, name ?: "", vllist);
 
 	down_write(&afs_cells_sem);
 	read_lock(&afs_cells_lock);
 	list_for_each_entry(cell, &afs_cells, link) {
-		if (strcasecmp(cell->name, name) == 0)
+		if (strncasecmp(cell->name, name, namesz) == 0)
 			goto duplicate_name;
 	}
 	read_unlock(&afs_cells_lock);
 
-	cell = afs_cell_alloc(name, vllist);
+	cell = afs_cell_alloc(name, namesz, vllist);
 	if (IS_ERR(cell)) {
 		_leave(" = %ld", PTR_ERR(cell));
 		up_write(&afs_cells_sem);
@@ -201,8 +203,18 @@ error:
 	return ERR_PTR(ret);
 
 duplicate_name:
+	if (retref && !IS_ERR(cell))
+		afs_get_cell(cell);
+
 	read_unlock(&afs_cells_lock);
 	up_write(&afs_cells_sem);
+
+	if (retref) {
+		_leave(" = %p", cell);
+		return cell;
+	}
+
+	_leave(" = -EEXIST");
 	return ERR_PTR(-EEXIST);
 }
 
@@ -233,7 +245,7 @@ int afs_cell_init(char *rootcell)
 		*cp++ = 0;
 
 	/* allocate a cell record for the root cell */
-	new_root = afs_cell_create(rootcell, cp);
+	new_root = afs_cell_create(rootcell, strlen(rootcell), cp, false);
 	if (IS_ERR(new_root)) {
 		_leave(" = %ld", PTR_ERR(new_root));
 		return PTR_ERR(new_root);
@@ -253,11 +265,12 @@ int afs_cell_init(char *rootcell)
 /*
  * lookup a cell record
  */
-struct afs_cell *afs_cell_lookup(const char *name, unsigned namesz)
+struct afs_cell *afs_cell_lookup(const char *name, unsigned namesz,
+				 bool dns_cell)
 {
 	struct afs_cell *cell;
 
-	_enter("\"%*.*s\",", namesz, namesz, name ? name : "");
+	_enter("\"%*.*s\",", namesz, namesz, name ?: "");
 
 	down_read(&afs_cells_sem);
 	read_lock(&afs_cells_lock);
@@ -271,6 +284,8 @@ struct afs_cell *afs_cell_lookup(const char *name, unsigned namesz)
 			}
 		}
 		cell = ERR_PTR(-ENOENT);
+		if (dns_cell)
+			goto create_cell;
 	found:
 		;
 	} else {
@@ -293,6 +308,15 @@ struct afs_cell *afs_cell_lookup(const char *name, unsigned namesz)
 	up_read(&afs_cells_sem);
 	_leave(" = %p", cell);
 	return cell;
+
+create_cell:
+	read_unlock(&afs_cells_lock);
+	up_read(&afs_cells_sem);
+
+	cell = afs_cell_create(name, namesz, NULL, true);
+
+	_leave(" = %p", cell);
+	return cell;
 }
 
 #if 0
diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index b42d5cc..0d38c09 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -477,6 +477,40 @@ static int afs_do_lookup(struct inode *dir, struct dentry *dentry,
 }
 
 /*
+ * Try to auto mount the mountpoint with pseudo directory, if the autocell
+ * operation is setted.
+ */
+static struct inode *afs_try_auto_mntpt(
+	int ret, struct dentry *dentry, struct inode *dir, struct key *key,
+	struct afs_fid *fid)
+{
+	const char *devname = dentry->d_name.name;
+	struct afs_vnode *vnode = AFS_FS_I(dir);
+	struct inode *inode;
+
+	_enter("%d, %p{%s}, {%x:%u}, %p",
+	       ret, dentry, devname, vnode->fid.vid, vnode->fid.vnode, key);
+
+	if (ret != -ENOENT ||
+	    !test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
+		goto out;
+
+	inode = afs_iget_autocell(dir, devname, strlen(devname), key);
+	if (IS_ERR(inode)) {
+		ret = PTR_ERR(inode);
+		goto out;
+	}
+
+	*fid = AFS_FS_I(inode)->fid;
+	_leave("= %p", inode);
+	return inode;
+
+out:
+	_leave("= %d", ret);
+	return ERR_PTR(ret);
+}
+
+/*
  * look up an entry in a directory
  */
 static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
@@ -520,6 +554,13 @@ static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
 
 	ret = afs_do_lookup(dir, dentry, &fid, key);
 	if (ret < 0) {
+		inode = afs_try_auto_mntpt(ret, dentry, dir, key, &fid);
+		if (!IS_ERR(inode)) {
+			key_put(key);
+			goto success;
+		}
+
+		ret = PTR_ERR(inode);
 		key_put(key);
 		if (ret == -ENOENT) {
 			d_add(dentry, NULL);
@@ -539,6 +580,7 @@ static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
 		return ERR_CAST(inode);
 	}
 
+success:
 	dentry->d_op = &afs_fs_dentry_operations;
 
 	d_add(dentry, inode);
@@ -696,8 +738,9 @@ static int afs_d_delete(struct dentry *dentry)
 		goto zap;
 
 	if (dentry->d_inode &&
-	    test_bit(AFS_VNODE_DELETED, &AFS_FS_I(dentry->d_inode)->flags))
-			goto zap;
+	    (test_bit(AFS_VNODE_DELETED,   &AFS_FS_I(dentry->d_inode)->flags) ||
+	     test_bit(AFS_VNODE_PSEUDODIR, &AFS_FS_I(dentry->d_inode)->flags)))
+		goto zap;
 
 	_leave(" = 0 [keep]");
 	return 0;
diff --git a/fs/afs/inode.c b/fs/afs/inode.c
index 320ffef..0747339 100644
--- a/fs/afs/inode.c
+++ b/fs/afs/inode.c
@@ -19,6 +19,8 @@
 #include <linux/fs.h>
 #include <linux/pagemap.h>
 #include <linux/sched.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
 #include "internal.h"
 
 struct afs_iget_data {
@@ -102,6 +104,16 @@ static int afs_iget5_test(struct inode *inode, void *opaque)
 }
 
 /*
+ * iget5() comparator for inode created by autocell operations
+ *
+ * These pseudo inodes don't match anything.
+ */
+static int afs_iget5_autocell_test(struct inode *inode, void *opaque)
+{
+	return 0;
+}
+
+/*
  * iget5() inode initialiser
  */
 static int afs_iget5_set(struct inode *inode, void *opaque)
@@ -118,6 +130,67 @@ static int afs_iget5_set(struct inode *inode, void *opaque)
 }
 
 /*
+ * inode retrieval for autocell
+ */
+struct inode *afs_iget_autocell(struct inode *dir, const char *dev_name,
+				int namesz, struct key *key)
+{
+	struct afs_iget_data data;
+	struct afs_super_info *as;
+	struct afs_vnode *vnode;
+	struct super_block *sb;
+	struct inode *inode;
+	static atomic_t afs_autocell_ino;
+
+	_enter("{%x:%u},%*.*s,",
+	       AFS_FS_I(dir)->fid.vid, AFS_FS_I(dir)->fid.vnode,
+	       namesz, namesz, dev_name ?: "");
+
+	sb = dir->i_sb;
+	as = sb->s_fs_info;
+	data.volume = as->volume;
+	data.fid.vid = as->volume->vid;
+	data.fid.unique = 0;
+	data.fid.vnode = 0;
+
+	inode = iget5_locked(sb, atomic_inc_return(&afs_autocell_ino),
+			     afs_iget5_autocell_test, afs_iget5_set,
+			     &data);
+	if (!inode) {
+		_leave(" = -ENOMEM");
+		return ERR_PTR(-ENOMEM);
+	}
+
+	_debug("GOT INODE %p { ino=%lu, vl=%x, vn=%x, u=%x }",
+	       inode, inode->i_ino, data.fid.vid, data.fid.vnode,
+	       data.fid.unique);
+
+	vnode = AFS_FS_I(inode);
+
+	/* there shouldn't be an existing inode */
+	BUG_ON(!(inode->i_state & I_NEW));
+
+	inode->i_size		= 0;
+	inode->i_mode		= S_IFDIR | S_IRUGO | S_IXUGO;
+	inode->i_op		= &afs_autocell_inode_operations;
+	inode->i_nlink		= 2;
+	inode->i_uid		= 0;
+	inode->i_gid		= 0;
+	inode->i_ctime.tv_sec	= get_seconds();
+	inode->i_ctime.tv_nsec	= 0;
+	inode->i_atime		= inode->i_mtime = inode->i_ctime;
+	inode->i_blocks		= 0;
+	inode->i_version	= 0;
+	inode->i_generation	= 0;
+
+	set_bit(AFS_VNODE_PSEUDODIR, &vnode->flags);
+	inode->i_flags |= S_NOATIME;
+	unlock_new_inode(inode);
+	_leave(" = %p", inode);
+	return inode;
+}
+
+/*
  * inode retrieval
  */
 struct inode *afs_iget(struct super_block *sb, struct key *key,
@@ -314,6 +387,19 @@ int afs_getattr(struct vfsmount *mnt, struct dentry *dentry,
 }
 
 /*
+ * discard an AFS inode
+ */
+int afs_drop_inode(struct inode *inode)
+{
+	_enter("");
+
+	if (test_bit(AFS_VNODE_PSEUDODIR, &AFS_FS_I(inode)->flags))
+		return generic_delete_inode(inode);
+	else
+		return generic_drop_inode(inode);
+}
+
+/*
  * clear an AFS inode
  */
 void afs_evict_inode(struct inode *inode)
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 8679089..ce12a2b 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -42,6 +42,7 @@ typedef enum {
 struct afs_mount_params {
 	bool			rwpath;		/* T if the parent should be considered R/W */
 	bool			force;		/* T to force cell type */
+	bool			autocell;	/* T if set auto mount operation */
 	afs_voltype_t		type;		/* type of volume requested */
 	int			volnamesz;	/* size of volume name */
 	const char		*volname;	/* name of volume to mount */
@@ -358,6 +359,8 @@ struct afs_vnode {
 #define AFS_VNODE_READLOCKED	7		/* set if vnode is read-locked on the server */
 #define AFS_VNODE_WRITELOCKED	8		/* set if vnode is write-locked on the server */
 #define AFS_VNODE_UNLOCKING	9		/* set if vnode is being unlocked on the server */
+#define AFS_VNODE_AUTOCELL	10		/* set if Vnode is an auto mount point */
+#define AFS_VNODE_PSEUDODIR	11		/* set if Vnode is a pseudo directory */
 
 	long			acl_order;	/* ACL check count (callback break count) */
 
@@ -468,8 +471,8 @@ extern struct list_head afs_proc_cells;
 
 #define afs_get_cell(C) do { atomic_inc(&(C)->usage); } while(0)
 extern int afs_cell_init(char *);
-extern struct afs_cell *afs_cell_create(const char *, char *);
-extern struct afs_cell *afs_cell_lookup(const char *, unsigned);
+extern struct afs_cell *afs_cell_create(const char *, unsigned, char *, bool);
+extern struct afs_cell *afs_cell_lookup(const char *, unsigned, bool);
 extern struct afs_cell *afs_grab_cell(struct afs_cell *);
 extern void afs_put_cell(struct afs_cell *);
 extern void afs_cell_purge(void);
@@ -558,6 +561,8 @@ extern int afs_fs_release_lock(struct afs_server *, struct key *,
 /*
  * inode.c
  */
+extern struct inode *afs_iget_autocell(struct inode *, const char *, int,
+				       struct key *);
 extern struct inode *afs_iget(struct super_block *, struct key *,
 			      struct afs_fid *, struct afs_file_status *,
 			      struct afs_callback *);
@@ -566,6 +571,7 @@ extern int afs_validate(struct afs_vnode *, struct key *);
 extern int afs_getattr(struct vfsmount *, struct dentry *, struct kstat *);
 extern int afs_setattr(struct dentry *, struct iattr *);
 extern void afs_evict_inode(struct inode *);
+extern int afs_drop_inode(struct inode *);
 
 /*
  * main.c
@@ -581,6 +587,7 @@ extern int afs_abort_to_error(u32);
  * mntpt.c
  */
 extern const struct inode_operations afs_mntpt_inode_operations;
+extern const struct inode_operations afs_autocell_inode_operations;
 extern const struct file_operations afs_mntpt_file_operations;
 
 extern int afs_mntpt_check_symlink(struct afs_vnode *, struct key *);
diff --git a/fs/afs/mntpt.c b/fs/afs/mntpt.c
index a9e2303..6d55268 100644
--- a/fs/afs/mntpt.c
+++ b/fs/afs/mntpt.c
@@ -38,6 +38,11 @@ const struct inode_operations afs_mntpt_inode_operations = {
 	.getattr	= afs_getattr,
 };
 
+const struct inode_operations afs_autocell_inode_operations = {
+	.follow_link	= afs_mntpt_follow_link,
+	.getattr	= afs_getattr,
+};
+
 static LIST_HEAD(afs_vfsmounts);
 static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
 
@@ -136,20 +141,16 @@ static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
 {
 	struct afs_super_info *super;
 	struct vfsmount *mnt;
+	struct afs_vnode *vnode;
 	struct page *page;
-	size_t size;
-	char *buf, *devname, *options;
+	char *devname, *options;
+	bool rwpath = false;
 	int ret;
 
 	_enter("{%s}", mntpt->d_name.name);
 
 	BUG_ON(!mntpt->d_inode);
 
-	ret = -EINVAL;
-	size = mntpt->d_inode->i_size;
-	if (size > PAGE_SIZE - 1)
-		goto error_no_devname;
-
 	ret = -ENOMEM;
 	devname = (char *) get_zeroed_page(GFP_KERNEL);
 	if (!devname)
@@ -159,28 +160,59 @@ static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
 	if (!options)
 		goto error_no_options;
 
-	/* read the contents of the AFS special symlink */
-	page = read_mapping_page(mntpt->d_inode->i_mapping, 0, NULL);
-	if (IS_ERR(page)) {
-		ret = PTR_ERR(page);
-		goto error_no_page;
+	vnode = AFS_FS_I(mntpt->d_inode);
+	if (test_bit(AFS_VNODE_PSEUDODIR, &vnode->flags)) {
+		/* if the directory is a pseudo directory, use the d_name */
+		static const char afs_root_cell[] = ":root.cell.";
+		unsigned size = mntpt->d_name.len;
+
+		ret = -ENOENT;
+		if (size < 2 || size > AFS_MAXCELLNAME)
+			goto error_no_page;
+
+		if (mntpt->d_name.name[0] == '.') {
+			devname[0] = '#';
+			memcpy(devname + 1, mntpt->d_name.name, size - 1);
+			memcpy(devname + size, afs_root_cell,
+			       sizeof(afs_root_cell));
+			rwpath = true;
+		} else {
+			devname[0] = '%';
+			memcpy(devname + 1, mntpt->d_name.name, size);
+			memcpy(devname + size + 1, afs_root_cell,
+			       sizeof(afs_root_cell));
+		}
+	} else {
+		/* read the contents of the AFS special symlink */
+		loff_t size = i_size_read(mntpt->d_inode);
+		char *buf;
+
+		ret = -EINVAL;
+		if (size > PAGE_SIZE - 1)
+			goto error_no_page;
+
+		page = read_mapping_page(mntpt->d_inode->i_mapping, 0, NULL);
+		if (IS_ERR(page)) {
+			ret = PTR_ERR(page);
+			goto error_no_page;
+		}
+
+		ret = -EIO;
+		if (PageError(page))
+			goto error;
+
+		buf = kmap_atomic(page, KM_USER0);
+		memcpy(devname, buf, size);
+		kunmap_atomic(buf, KM_USER0);
+		page_cache_release(page);
+		page = NULL;
 	}
 
-	ret = -EIO;
-	if (PageError(page))
-		goto error;
-
-	buf = kmap_atomic(page, KM_USER0);
-	memcpy(devname, buf, size);
-	kunmap_atomic(buf, KM_USER0);
-	page_cache_release(page);
-	page = NULL;
-
 	/* work out what options we want */
 	super = AFS_FS_S(mntpt->d_sb);
 	memcpy(options, "cell=", 5);
 	strcpy(options + 5, super->volume->cell->name);
-	if (super->volume->type == AFSVL_RWVOL)
+	if (super->volume->type == AFSVL_RWVOL || rwpath)
 		strcat(options, ",rwpath");
 
 	/* try and do the mount */
diff --git a/fs/afs/proc.c b/fs/afs/proc.c
index 852739d..096b23f 100644
--- a/fs/afs/proc.c
+++ b/fs/afs/proc.c
@@ -294,7 +294,7 @@ static ssize_t afs_proc_cells_write(struct file *file, const char __user *buf,
 	if (strcmp(kbuf, "add") == 0) {
 		struct afs_cell *cell;
 
-		cell = afs_cell_create(name, args);
+		cell = afs_cell_create(name, strlen(name), args, false);
 		if (IS_ERR(cell)) {
 			ret = PTR_ERR(cell);
 			goto done;
diff --git a/fs/afs/super.c b/fs/afs/super.c
index 9cf80f0..77e1e5a 100644
--- a/fs/afs/super.c
+++ b/fs/afs/super.c
@@ -16,6 +16,7 @@
 
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/mount.h>
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/smp_lock.h>
@@ -48,6 +49,7 @@ struct file_system_type afs_fs_type = {
 static const struct super_operations afs_super_ops = {
 	.statfs		= afs_statfs,
 	.alloc_inode	= afs_alloc_inode,
+	.drop_inode	= afs_drop_inode,
 	.destroy_inode	= afs_destroy_inode,
 	.evict_inode	= afs_evict_inode,
 	.put_super	= afs_put_super,
@@ -62,12 +64,14 @@ enum {
 	afs_opt_cell,
 	afs_opt_rwpath,
 	afs_opt_vol,
+	afs_opt_autocell,
 };
 
 static const match_table_t afs_options_list = {
 	{ afs_opt_cell,		"cell=%s"	},
 	{ afs_opt_rwpath,	"rwpath"	},
 	{ afs_opt_vol,		"vol=%s"	},
+	{ afs_opt_autocell,	"autocell"	},
 	{ afs_no_opt,		NULL		},
 };
 
@@ -151,7 +155,8 @@ static int afs_parse_options(struct afs_mount_params *params,
 		switch (token) {
 		case afs_opt_cell:
 			cell = afs_cell_lookup(args[0].from,
-					       args[0].to - args[0].from);
+					       args[0].to - args[0].from,
+					       false);
 			if (IS_ERR(cell))
 				return PTR_ERR(cell);
 			afs_put_cell(params->cell);
@@ -166,6 +171,10 @@ static int afs_parse_options(struct afs_mount_params *params,
 			*devname = args[0].from;
 			break;
 
+		case afs_opt_autocell:
+			params->autocell = 1;
+			break;
+
 		default:
 			printk(KERN_ERR "kAFS:"
 			       " Unknown or invalid mount option: '%s'\n", p);
@@ -252,10 +261,10 @@ static int afs_parse_device_name(struct afs_mount_params *params,
 
 	/* lookup the cell record */
 	if (cellname || !params->cell) {
-		cell = afs_cell_lookup(cellname, cellnamesz);
+		cell = afs_cell_lookup(cellname, cellnamesz, true);
 		if (IS_ERR(cell)) {
-			printk(KERN_ERR "kAFS: unable to lookup cell '%s'\n",
-			       cellname ?: "");
+			printk(KERN_ERR "kAFS: unable to lookup cell '%*.*s'\n",
+			       cellnamesz, cellnamesz, cellname ?: "");
 			return PTR_ERR(cell);
 		}
 		afs_put_cell(params->cell);
@@ -321,6 +330,9 @@ static int afs_fill_super(struct super_block *sb, void *data)
 	if (IS_ERR(inode))
 		goto error_inode;
 
+	if (params->autocell)
+		set_bit(AFS_VNODE_AUTOCELL, &AFS_FS_I(inode)->flags);
+
 	ret = -ENOMEM;
 	root = d_alloc_root(inode);
 	if (!root)