[PATCH 0/6] afs: DNS and VL server handling improvements

[PATCH 0/6] afs: DNS and VL server handling improvements

[David Howells]

Hi Al,

Here's a set of patches that improves Volume Location server handling in
the AFS filesystem and improves the DNS resolver code to allow server lists
(with addresses, priorities and weights for each server).

The highlights of this patchset are:

 (1) Permit a binary blob to be attached to be attached to a dns_resolver
     type key in lieu of a text one.  The first byte of the payload must be
     0 to cause existing text parsers to error out with EINVAL.  However,
     the "server list" feature must be requested by putting "srv=1" into
     the callout info, which is passed to the upcall.

 (2) Clean up the address list handling in AFS.

 (3) Introduce a 'VL server list' concept in AFS with rotation, analogous
     to the fileserver list and rotation.  For the moment VL server
     rotation takes a simple round-robin approach and pays no attention to
     the priority and weight assigned to each server.

The patches will work as-is with the current keyutils package as the
"srv=1" option will just be ignored and a text list of addresses will be
used to instantiate the key.  The modified AFS code still handles this.

To make the server list feature work properly, the keyutils package will
need updating to 1.5.12, the proposed commits for which can be found here:

	https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/keyutils.git/log/?h=next

that will allow the program run by request-key to be overridden for
"afsdb:" dns_resolver keys by the kafs-client program.  The kafs-client
program changes to make server list resolving work can be found here:

	http://git.infradead.org/users/dhowells/kafs-client.git/shortlog/refs/heads/next

along with code to allow static configuration to be used instead.


The kernel patches can be found here also:

	http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/?h=afs-dns

David
---
David Howells (6):
      dns: Allow the dns resolver to retrieve a server set
      afs: Do better max capacity handling on address lists
      afs: afs_end_vnode_operation() needs to translate abort codes to errors
      afs: Differentiate VL servers
      afs: Always build address lists using the helper functions
      afs: Sort address lists so that they are in logical ascending order


 fs/afs/Makefile              |    2 
 fs/afs/addr_list.c           |  209 ++++++++++++++----------------
 fs/afs/cell.c                |   39 +++---
 fs/afs/dynroot.c             |    2 
 fs/afs/internal.h            |  114 ++++++++++++++---
 fs/afs/proc.c                |   44 +++---
 fs/afs/rotate.c              |    6 -
 fs/afs/server.c              |   42 ++----
 fs/afs/vl_list.c             |  289 ++++++++++++++++++++++++++++++++++++++++++
 fs/afs/vl_rotate.c           |  239 +++++++++++++++++++++++++++++++++++
 fs/afs/vlclient.c            |   32 ++---
 fs/afs/volume.c              |   52 ++------
 net/dns_resolver/dns_key.c   |   61 ++++++++-
 net/dns_resolver/dns_query.c |    5 -
 14 files changed, 866 insertions(+), 270 deletions(-)
 create mode 100644 fs/afs/vl_list.c
 create mode 100644 fs/afs/vl_rotate.c

[PATCH 1/6] dns: Allow the dns resolver to retrieve a server set

[David Howells]

Allow the DNS resolver to retrieve a set of servers and their associated
addresses, ports, preference and weight ratings.

In terms of communication with userspace, "srv=1" is added to the callout
string (the '1' indicating the maximum data version supported by the
kernel) to ask the userspace side for this.

If the userspace side doesn't recognise it, it will ignore the option and
return the usual text address list.

If the userspace side does recognise it, it will return some binary data
that begins with a zero byte that would cause the string parsers to give an
error.  The second byte contains the version of the data in the blob (this
may be between 1 and the version specified in the callout data).  The
remainder of the payload is version-specific.

In version 1, the payload looks like (note that this is packed):

	u8	Non-string marker (ie. 0)
	u8	Content (0 => Server list)
	u8	Version (ie. 1)
	u8	Number of servers
	foreach-server {
		u16	Name length (LE)
		u16	Priority (as per SRV record) (LE)
		u16	Weight (as per SRV record) (LE)
		u16	Port (LE)
		u8	Protocol (IPPROTO_*)
		u8	Number of addresses
		char[]	Name (not NUL-terminated)
		foreach-address {
			u8		Family (AF_INET{,6})
			union {
				u8[4]	ipv4_addr
				u8[16]	ipv6_addr
			}
		}
	}

This can then be used to fetch a whole cell's configuration for AFS, for
example.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 net/dns_resolver/dns_key.c   |   61 ++++++++++++++++++++++++++++++++++++++++--
 net/dns_resolver/dns_query.c |    5 +--
 2 files changed, 59 insertions(+), 7 deletions(-)

diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c
index 7f4534828f6c..ac3c9aa75727 100644
--- a/net/dns_resolver/dns_key.c
+++ b/net/dns_resolver/dns_key.c
@@ -48,14 +48,40 @@ const struct cred *dns_resolver_cache;
 /*
  * Preparse instantiation data for a dns_resolver key.
  *
- * The data must be a NUL-terminated string, with the NUL char accounted in
- * datalen.
+ * For normal hostname lookups, the data must be a NUL-terminated string, with
+ * the NUL char accounted in datalen.
  *
  * If the data contains a '#' characters, then we take the clause after each
  * one to be an option of the form 'key=value'.  The actual data of interest is
  * the string leading up to the first '#'.  For instance:
  *
  *        "ip1,ip2,...#foo=bar"
+ *
+ * For server list requests, the data must begin with a NUL char and be
+ * followed by a byte indicating the version of the data format.  Version 1
+ * looks something like (note this is packed):
+ *
+ *	u8      Non-string marker (ie. 0)
+ *	u8	Content (0 is server list)
+ *	u8	Version (ie. 1)
+ *	u8	Number of servers
+ *	foreach-server {
+ *		u16	Name length (LE)
+ *		u16	Priority (as per SRV record, low first) (LE)
+ *		u16	Weight (as per SRV record, higher first) (LE)
+ *		u16	Port (LE)
+ *		u8	Protocol (IPPROTO_*)
+ *		u8	Number of addresses
+ *		char[]	Name (not NUL-terminated)
+ *		foreach-address {
+ *			u8		Family (AF_INET{,6})
+ *			union {
+ *				u8[4]	ipv4_addr
+ *				u8[16]	ipv6_addr
+ *			}
+ *		}
+ *	}
+ *
  */
 static int
 dns_resolver_preparse(struct key_preparsed_payload *prep)
@@ -66,9 +92,37 @@ dns_resolver_preparse(struct key_preparsed_payload *prep)
 	int datalen = prep->datalen, result_len = 0;
 	const char *data = prep->data, *end, *opt;
 
+	if (datalen <= 1 || !data)
+		return -EINVAL;
+
+	if (data[0] == 0) {
+		/* It may be a server list. */
+		if (datalen <= 3)
+			return -EINVAL;
+
+		data++;
+		kenter("[%u,%u],%u", data[0], data[1], datalen);
+		if (data[0] != 0) {
+			pr_warn_ratelimited(
+				"dns_resolver: Unsupported result type (%u)\n",
+				(unsigned char)data[0]);
+			return -EINVAL;
+		}
+
+		if (data[1] != 1) {
+			pr_warn_ratelimited(
+				"dns_resolver: Unsupported server list version (%u)\n",
+				(unsigned char)data[1]);
+			return -EINVAL;
+		}
+
+		result_len = datalen - 1;
+		goto store_result;
+	}
+
 	kenter("'%*.*s',%u", datalen, datalen, data, datalen);
 
-	if (datalen <= 1 || !data || data[datalen - 1] != '\0')
+	if (!data || data[datalen - 1] != '\0')
 		return -EINVAL;
 	datalen--;
 
@@ -144,6 +198,7 @@ dns_resolver_preparse(struct key_preparsed_payload *prep)
 		return 0;
 	}
 
+store_result:
 	kdebug("store result");
 	prep->quotalen = result_len;
 
diff --git a/net/dns_resolver/dns_query.c b/net/dns_resolver/dns_query.c
index 49da67034f29..76338c38738a 100644
--- a/net/dns_resolver/dns_query.c
+++ b/net/dns_resolver/dns_query.c
@@ -148,12 +148,9 @@ int dns_query(const char *type, const char *name, size_t namelen,
 
 	if (_result) {
 		ret = -ENOMEM;
-		*_result = kmalloc(len + 1, GFP_KERNEL);
+		*_result = kmemdup_nul(upayload->data, len, GFP_KERNEL);
 		if (!*_result)
 			goto put;
-
-		memcpy(*_result, upayload->data, len);
-		(*_result)[len] = '\0';
 	}
 
 	if (_expiry)

[PATCH 2/6] afs: Do better max capacity handling on address lists

[David Howells]

Note the maximum allocated capacity in an afs_addr_list struct and discard
addresses that would exceed it in afs_merge_fs_addr{4,6}().

Also, since the current maximum capacity is less than 255, reduce the
relevant members to bytes.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/afs/addr_list.c |   19 +++++++++++--------
 fs/afs/internal.h  |    8 +++++---
 2 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/fs/afs/addr_list.c b/fs/afs/addr_list.c
index 025a9a5e1c32..4dbb8af54668 100644
--- a/fs/afs/addr_list.c
+++ b/fs/afs/addr_list.c
@@ -17,11 +17,6 @@
 #include "internal.h"
 #include "afs_fs.h"
 
-//#define AFS_MAX_ADDRESSES
-//	((unsigned int)((PAGE_SIZE - sizeof(struct afs_addr_list)) /
-//			sizeof(struct sockaddr_rxrpc)))
-#define AFS_MAX_ADDRESSES ((unsigned int)(sizeof(unsigned long) * 8))
-
 /*
  * Release an address list.
  */
@@ -43,11 +38,15 @@ struct afs_addr_list *afs_alloc_addrlist(unsigned int nr,
 
 	_enter("%u,%u,%u", nr, service, port);
 
+	if (nr > AFS_MAX_ADDRESSES)
+		nr = AFS_MAX_ADDRESSES;
+
 	alist = kzalloc(struct_size(alist, addrs, nr), GFP_KERNEL);
 	if (!alist)
 		return NULL;
 
 	refcount_set(&alist->usage, 1);
+	alist->max_addrs = nr;
 
 	for (i = 0; i < nr; i++) {
 		struct sockaddr_rxrpc *srx = &alist->addrs[i];
@@ -109,8 +108,6 @@ struct afs_addr_list *afs_parse_text_addrs(const char *text, size_t len,
 	} while (p < end);
 
 	_debug("%u/%u addresses", nr, AFS_MAX_ADDRESSES);
-	if (nr > AFS_MAX_ADDRESSES)
-		nr = AFS_MAX_ADDRESSES;
 
 	alist = afs_alloc_addrlist(nr, service, port);
 	if (!alist)
@@ -180,7 +177,7 @@ struct afs_addr_list *afs_parse_text_addrs(const char *text, size_t len,
 		}
 
 		alist->nr_addrs++;
-	} while (p < end && alist->nr_addrs < AFS_MAX_ADDRESSES);
+	} while (p < end && alist->nr_addrs < alist->max_addrs);
 
 	_leave(" = [nr %u]", alist->nr_addrs);
 	return alist;
@@ -241,6 +238,9 @@ void afs_merge_fs_addr4(struct afs_addr_list *alist, __be32 xdr, u16 port)
 	__be16 xport = htons(port);
 	int i;
 
+	if (alist->nr_addrs >= alist->max_addrs)
+		return;
+
 	for (i = 0; i < alist->nr_ipv4; i++) {
 		a = &alist->addrs[i].transport.sin6;
 		if (xdr == a->sin6_addr.s6_addr32[3] &&
@@ -277,6 +277,9 @@ void afs_merge_fs_addr6(struct afs_addr_list *alist, __be32 *xdr, u16 port)
 	__be16 xport = htons(port);
 	int i, diff;
 
+	if (alist->nr_addrs >= alist->max_addrs)
+		return;
+
 	for (i = alist->nr_ipv4; i < alist->nr_addrs; i++) {
 		a = &alist->addrs[i].transport.sin6;
 		diff = memcmp(xdr, &a->sin6_addr, 16);
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 871a228d7f37..8ae4e2ebb99a 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -73,12 +73,14 @@ struct afs_addr_list {
 	struct rcu_head		rcu;		/* Must be first */
 	refcount_t		usage;
 	u32			version;	/* Version */
-	unsigned short		nr_addrs;
-	unsigned short		index;		/* Address currently in use */
-	unsigned short		nr_ipv4;	/* Number of IPv4 addresses */
+	unsigned char		max_addrs;
+	unsigned char		nr_addrs;
+	unsigned char		index;		/* Address currently in use */
+	unsigned char		nr_ipv4;	/* Number of IPv4 addresses */
 	unsigned long		probed;		/* Mask of servers that have been probed */
 	unsigned long		yfs;		/* Mask of servers that are YFS */
 	struct sockaddr_rxrpc	addrs[];
+#define AFS_MAX_ADDRESSES ((unsigned int)(sizeof(unsigned long) * 8))
 };
 
 /*

[PATCH 3/6] afs: afs_end_vnode_operation() needs to translate abort codes to errors

[David Howells]

afs_end_vnode_operation() calls the function to translate an abort code
into an error return, but never actually assigns the error.

Fix this by storing the looked up error back into the cursor.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/afs/rotate.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/fs/afs/rotate.c b/fs/afs/rotate.c
index 1faef56b12bd..add0dbb18763 100644
--- a/fs/afs/rotate.c
+++ b/fs/afs/rotate.c
@@ -512,7 +512,6 @@ bool afs_select_current_fileserver(struct afs_fs_cursor *fc)
 int afs_end_vnode_operation(struct afs_fs_cursor *fc)
 {
 	struct afs_net *net = afs_v2net(fc->vnode);
-	int ret;
 
 	mutex_unlock(&fc->vnode->io_lock);
 
@@ -520,9 +519,8 @@ int afs_end_vnode_operation(struct afs_fs_cursor *fc)
 	afs_put_cb_interest(net, fc->cbi);
 	afs_put_serverlist(net, fc->server_list);
 
-	ret = fc->ac.error;
-	if (ret == -ECONNABORTED)
-		afs_abort_to_error(fc->ac.abort_code);
+	if (fc->ac.error == -ECONNABORTED)
+		fc->ac.error = afs_abort_to_error(fc->ac.abort_code);
 
 	return fc->ac.error;
 }

[PATCH 4/6] afs: Differentiate VL servers

[David Howells]

Differentiate between VL servers rather than lumping all their addresses
together into one set by:

 (1) Add the concept of a VL server list, where each server has its own
     separate address list.  This code is similar to the FS server list.

 (2) Use the DNS resolver to retrieve a set of servers and their associated
     addresses, ports, preference and weight ratings.

 (3) In the case of a legacy DNS resolver or an address list given directly
     through /proc/net/afs/cells, create a list containing just a dummy
     server record and attach all the addresses to that.

 (4) Implement a simple rotation policy, for the moment ignoring the
     priorities and weights assigned to the servers.

 (5) Show the address list through /proc/net/afs/<cell>/vlservers.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/afs/Makefile    |    2 
 fs/afs/addr_list.c |  109 ++++++++------------
 fs/afs/cell.c      |   39 ++++---
 fs/afs/dynroot.c   |    2 
 fs/afs/internal.h  |  106 +++++++++++++++++--
 fs/afs/proc.c      |   44 ++++----
 fs/afs/server.c    |   42 ++------
 fs/afs/vl_list.c   |  289 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/afs/vl_rotate.c |  239 +++++++++++++++++++++++++++++++++++++++++++
 fs/afs/vlclient.c  |   32 +++---
 fs/afs/volume.c    |   52 +++------
 11 files changed, 751 insertions(+), 205 deletions(-)
 create mode 100644 fs/afs/vl_list.c
 create mode 100644 fs/afs/vl_rotate.c

diff --git a/fs/afs/Makefile b/fs/afs/Makefile
index 546874057bd3..03e9f7afea1b 100644
--- a/fs/afs/Makefile
+++ b/fs/afs/Makefile
@@ -29,6 +29,8 @@ kafs-y := \
 	super.o \
 	netdevices.o \
 	vlclient.o \
+	vl_rotate.o \
+	vl_list.o \
 	volume.o \
 	write.o \
 	xattr.o
diff --git a/fs/afs/addr_list.c b/fs/afs/addr_list.c
index 4dbb8af54668..630f91633b40 100644
--- a/fs/afs/addr_list.c
+++ b/fs/afs/addr_list.c
@@ -64,14 +64,17 @@ struct afs_addr_list *afs_alloc_addrlist(unsigned int nr,
 /*
  * Parse a text string consisting of delimited addresses.
  */
-struct afs_addr_list *afs_parse_text_addrs(const char *text, size_t len,
-					   char delim,
-					   unsigned short service,
-					   unsigned short port)
+struct afs_vlserver_list *afs_parse_text_addrs(struct afs_net *net,
+					       const char *text, size_t len,
+					       char delim,
+					       unsigned short service,
+					       unsigned short port)
 {
+	struct afs_vlserver_list *vllist;
 	struct afs_addr_list *alist;
 	const char *p, *end = text + len;
 	unsigned int nr = 0;
+	int ret = -ENOMEM;
 
 	_enter("%*.*s,%c", (int)len, (int)len, text, delim);
 
@@ -109,10 +112,20 @@ struct afs_addr_list *afs_parse_text_addrs(const char *text, size_t len,
 
 	_debug("%u/%u addresses", nr, AFS_MAX_ADDRESSES);
 
-	alist = afs_alloc_addrlist(nr, service, port);
-	if (!alist)
+	vllist = afs_alloc_vlserver_list(1);
+	if (!vllist)
 		return ERR_PTR(-ENOMEM);
 
+	vllist->nr_servers = 1;
+	vllist->servers[0].server = afs_alloc_vlserver("<dummy>", 7, AFS_VL_PORT);
+	if (!vllist->servers[0].server)
+		goto error;
+
+	alist = afs_alloc_addrlist(nr, service, AFS_VL_PORT);
+	if (!alist)
+		goto error;
+	vllist->servers[0].server->addresses = alist;
+
 	/* Extract the addresses */
 	p = text;
 	do {
@@ -180,11 +193,13 @@ struct afs_addr_list *afs_parse_text_addrs(const char *text, size_t len,
 	} while (p < end && alist->nr_addrs < alist->max_addrs);
 
 	_leave(" = [nr %u]", alist->nr_addrs);
-	return alist;
+	return vllist;
 
 bad_address:
-	kfree(alist);
-	return ERR_PTR(-EINVAL);
+	ret = -EINVAL;
+error:
+	afs_put_vlserverlist(net, vllist);
+	return ERR_PTR(ret);
 }
 
 /*
@@ -203,30 +218,34 @@ static int afs_cmp_addr_list(const struct afs_addr_list *a1,
 /*
  * Perform a DNS query for VL servers and build a up an address list.
  */
-struct afs_addr_list *afs_dns_query(struct afs_cell *cell, time64_t *_expiry)
+struct afs_vlserver_list *afs_dns_query(struct afs_cell *cell, time64_t *_expiry)
 {
-	struct afs_addr_list *alist;
-	char *vllist = NULL;
+	struct afs_vlserver_list *vllist;
+	char *result = NULL;
 	int ret;
 
 	_enter("%s", cell->name);
 
-	ret = dns_query("afsdb", cell->name, cell->name_len,
-			"", &vllist, _expiry);
-	if (ret < 0)
+	ret = dns_query("afsdb", cell->name, cell->name_len, "srv=1",
+			&result, _expiry);
+	if (ret < 0) {
+		kleave(" = %d [dns]", ret);
 		return ERR_PTR(ret);
-
-	alist = afs_parse_text_addrs(vllist, strlen(vllist), ',',
-				     VL_SERVICE, AFS_VL_PORT);
-	if (IS_ERR(alist)) {
-		kfree(vllist);
-		if (alist != ERR_PTR(-ENOMEM))
-			pr_err("Failed to parse DNS data\n");
-		return alist;
 	}
 
-	kfree(vllist);
-	return alist;
+	if (*_expiry == 0)
+		*_expiry = ktime_get_real_seconds() + 60;
+
+	if (ret > 1 && result[0] == 0)
+		vllist = afs_extract_vlserver_list(cell, result, ret);
+	else
+		vllist = afs_parse_text_addrs(cell->net, result, ret, ',',
+					      VL_SERVICE, AFS_VL_PORT);
+	kfree(result);
+	if (IS_ERR(vllist) && vllist != ERR_PTR(-ENOMEM))
+		pr_err("Failed to parse DNS data\n");
+
+	return vllist;
 }
 
 /*
@@ -353,43 +372,3 @@ int afs_end_cursor(struct afs_addr_cursor *ac)
 	ac->begun = false;
 	return ac->error;
 }
-
-/*
- * Set the address cursor for iterating over VL servers.
- */
-int afs_set_vl_cursor(struct afs_addr_cursor *ac, struct afs_cell *cell)
-{
-	struct afs_addr_list *alist;
-	int ret;
-
-	if (!rcu_access_pointer(cell->vl_addrs)) {
-		ret = wait_on_bit(&cell->flags, AFS_CELL_FL_NO_LOOKUP_YET,
-				  TASK_INTERRUPTIBLE);
-		if (ret < 0)
-			return ret;
-
-		if (!rcu_access_pointer(cell->vl_addrs) &&
-		    ktime_get_real_seconds() < cell->dns_expiry)
-			return cell->error;
-	}
-
-	read_lock(&cell->vl_addrs_lock);
-	alist = rcu_dereference_protected(cell->vl_addrs,
-					  lockdep_is_held(&cell->vl_addrs_lock));
-	if (alist->nr_addrs > 0)
-		afs_get_addrlist(alist);
-	else
-		alist = NULL;
-	read_unlock(&cell->vl_addrs_lock);
-
-	if (!alist)
-		return -EDESTADDRREQ;
-
-	ac->alist = alist;
-	ac->addr = NULL;
-	ac->start = READ_ONCE(alist->index);
-	ac->index = ac->start;
-	ac->error = 0;
-	ac->begun = false;
-	return 0;
-}
diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index f3d0bef16d78..0bb54de08f39 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -119,7 +119,7 @@ struct afs_cell *afs_lookup_cell_rcu(struct afs_net *net,
  */
 static struct afs_cell *afs_alloc_cell(struct afs_net *net,
 				       const char *name, unsigned int namelen,
-				       const char *vllist)
+				       const char *addresses)
 {
 	struct afs_cell *cell;
 	int i, ret;
@@ -134,7 +134,7 @@ static struct afs_cell *afs_alloc_cell(struct afs_net *net,
 	if (namelen == 5 && memcmp(name, "@cell", 5) == 0)
 		return ERR_PTR(-EINVAL);
 
-	_enter("%*.*s,%s", namelen, namelen, name, vllist);
+	_enter("%*.*s,%s", namelen, namelen, name, addresses);
 
 	cell = kzalloc(sizeof(struct afs_cell), GFP_KERNEL);
 	if (!cell) {
@@ -153,22 +153,23 @@ static struct afs_cell *afs_alloc_cell(struct afs_net *net,
 		       (1 << AFS_CELL_FL_NO_LOOKUP_YET));
 	INIT_LIST_HEAD(&cell->proc_volumes);
 	rwlock_init(&cell->proc_lock);
-	rwlock_init(&cell->vl_addrs_lock);
+	rwlock_init(&cell->vl_servers_lock);
 
 	/* Fill in the VL server list if we were given a list of addresses to
 	 * use.
 	 */
-	if (vllist) {
-		struct afs_addr_list *alist;
-
-		alist = afs_parse_text_addrs(vllist, strlen(vllist), ':',
-					     VL_SERVICE, AFS_VL_PORT);
-		if (IS_ERR(alist)) {
-			ret = PTR_ERR(alist);
+	if (addresses) {
+		struct afs_vlserver_list *vllist;
+
+		vllist = afs_parse_text_addrs(net,
+					      addresses, strlen(addresses), ':',
+					      VL_SERVICE, AFS_VL_PORT);
+		if (IS_ERR(vllist)) {
+			ret = PTR_ERR(vllist);
 			goto parse_failed;
 		}
 
-		rcu_assign_pointer(cell->vl_addrs, alist);
+		rcu_assign_pointer(cell->vl_servers, vllist);
 		cell->dns_expiry = TIME64_MAX;
 	}
 
@@ -356,14 +357,14 @@ int afs_cell_init(struct afs_net *net, const char *rootcell)
  */
 static void afs_update_cell(struct afs_cell *cell)
 {
-	struct afs_addr_list *alist, *old;
+	struct afs_vlserver_list *vllist, *old;
 	time64_t now, expiry;
 
 	_enter("%s", cell->name);
 
-	alist = afs_dns_query(cell, &expiry);
-	if (IS_ERR(alist)) {
-		switch (PTR_ERR(alist)) {
+	vllist = afs_dns_query(cell, &expiry);
+	if (IS_ERR(vllist)) {
+		switch (PTR_ERR(vllist)) {
 		case -ENODATA:
 			/* The DNS said that the cell does not exist */
 			set_bit(AFS_CELL_FL_NOT_FOUND, &cell->flags);
@@ -387,12 +388,12 @@ static void afs_update_cell(struct afs_cell *cell)
 		/* Exclusion on changing vl_addrs is achieved by a
 		 * non-reentrant work item.
 		 */
-		old = rcu_dereference_protected(cell->vl_addrs, true);
-		rcu_assign_pointer(cell->vl_addrs, alist);
+		old = rcu_dereference_protected(cell->vl_servers, true);
+		rcu_assign_pointer(cell->vl_servers, vllist);
 		cell->dns_expiry = expiry;
 
 		if (old)
-			afs_put_addrlist(old);
+			afs_put_vlserverlist(cell->net, old);
 	}
 
 	if (test_and_clear_bit(AFS_CELL_FL_NO_LOOKUP_YET, &cell->flags))
@@ -414,7 +415,7 @@ static void afs_cell_destroy(struct rcu_head *rcu)
 
 	ASSERTCMP(atomic_read(&cell->usage), ==, 0);
 
-	afs_put_addrlist(rcu_access_pointer(cell->vl_addrs));
+	afs_put_vlserverlist(cell->net, rcu_access_pointer(cell->vl_servers));
 	key_put(cell->anonymous_key);
 	kfree(cell);
 
diff --git a/fs/afs/dynroot.c b/fs/afs/dynroot.c
index 1cde710a8013..42e404ac3ff6 100644
--- a/fs/afs/dynroot.c
+++ b/fs/afs/dynroot.c
@@ -46,7 +46,7 @@ static int afs_probe_cell_name(struct dentry *dentry)
 		return 0;
 	}
 
-	ret = dns_query("afsdb", name, len, "", NULL, NULL);
+	ret = dns_query("afsdb", name, len, "srv=1", NULL, NULL);
 	if (ret == -ENODATA)
 		ret = -EDESTADDRREQ;
 	return ret;
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 8ae4e2ebb99a..638c157fc387 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -343,12 +343,47 @@ struct afs_cell {
 	rwlock_t		proc_lock;
 
 	/* VL server list. */
-	rwlock_t		vl_addrs_lock;	/* Lock on vl_addrs */
-	struct afs_addr_list	__rcu *vl_addrs; /* List of VL servers */
+	rwlock_t		vl_servers_lock; /* Lock on vl_servers */
+	struct afs_vlserver_list *__rcu vl_servers;
+
 	u8			name_len;	/* Length of name */
 	char			name[64 + 1];	/* Cell name, case-flattened and NUL-padded */
 };
 
+/*
+ * Volume Location server record.
+ */
+struct afs_vlserver {
+	struct rcu_head		rcu;
+	struct afs_addr_list	__rcu *addresses; /* List of addresses for this VL server */
+	unsigned long		flags;
+#define AFS_VLSERVER_FL_PROBED	0		/* The VL server has been probed */
+#define AFS_VLSERVER_FL_PROBING	1		/* VL server is being probed */
+	rwlock_t		lock;		/* Lock on addresses */
+	atomic_t		usage;
+	u16			name_len;	/* Length of name */
+	u16			port;
+	char			name[];		/* Server name, case-flattened */
+};
+
+/*
+ * Weighted list of Volume Location servers.
+ */
+struct afs_vlserver_entry {
+	u16			priority;	/* Preference (as SRV) */
+	u16			weight;		/* Weight (as SRV) */
+	struct afs_vlserver	*server;
+};
+
+struct afs_vlserver_list {
+	struct rcu_head		rcu;
+	atomic_t		usage;
+	unsigned short		nr_servers;
+	unsigned short		index;		/* Server currently in use */
+	rwlock_t		lock;
+	struct afs_vlserver_entry servers[];
+};
+
 /*
  * Cached VLDB entry.
  *
@@ -595,6 +630,22 @@ struct afs_addr_cursor {
 	bool			responded;	/* T if the current address responded */
 };
 
+/*
+ * Cursor for iterating over a set of volume location servers.
+ */
+struct afs_vl_cursor {
+	struct afs_addr_cursor	ac;
+	struct afs_cell		*cell;		/* The cell we're querying */
+	struct afs_vlserver_list *server_list;	/* Current server list (pins ref) */
+	struct key		*key;		/* Key for the server */
+	unsigned char		start;		/* Initial index in server list */
+	unsigned char		index;		/* Number of servers tried beyond start */
+	unsigned short		flags;
+#define AFS_VL_CURSOR_STOP	0x0001		/* Set to cease iteration */
+#define AFS_VL_CURSOR_RETRY	0x0002		/* Set to do a retry */
+#define AFS_VL_CURSOR_RETRIED	0x0004		/* Set if started a retry */
+};
+
 /*
  * Cursor for iterating over a set of fileservers.
  */
@@ -640,12 +691,12 @@ extern struct afs_addr_list *afs_alloc_addrlist(unsigned int,
 						unsigned short,
 						unsigned short);
 extern void afs_put_addrlist(struct afs_addr_list *);
-extern struct afs_addr_list *afs_parse_text_addrs(const char *, size_t, char,
-						  unsigned short, unsigned short);
-extern struct afs_addr_list *afs_dns_query(struct afs_cell *, time64_t *);
+extern struct afs_vlserver_list *afs_parse_text_addrs(struct afs_net *,
+						      const char *, size_t, char,
+						      unsigned short, unsigned short);
+extern struct afs_vlserver_list *afs_dns_query(struct afs_cell *, time64_t *);
 extern bool afs_iterate_addresses(struct afs_addr_cursor *);
 extern int afs_end_cursor(struct afs_addr_cursor *);
-extern int afs_set_vl_cursor(struct afs_addr_cursor *, struct afs_cell *);
 
 extern void afs_merge_fs_addr4(struct afs_addr_list *, __be32, u16);
 extern void afs_merge_fs_addr6(struct afs_addr_list *, __be32 *, u16);
@@ -1039,14 +1090,43 @@ extern void afs_fs_exit(void);
 /*
  * vlclient.c
  */
-extern struct afs_vldb_entry *afs_vl_get_entry_by_name_u(struct afs_net *,
-							 struct afs_addr_cursor *,
-							 struct key *, const char *, int);
-extern struct afs_addr_list *afs_vl_get_addrs_u(struct afs_net *, struct afs_addr_cursor *,
-						struct key *, const uuid_t *);
+extern struct afs_vldb_entry *afs_vl_get_entry_by_name_u(struct afs_vl_cursor *,
+							 const char *, int);
+extern struct afs_addr_list *afs_vl_get_addrs_u(struct afs_vl_cursor *, const uuid_t *);
 extern int afs_vl_get_capabilities(struct afs_net *, struct afs_addr_cursor *, struct key *);
-extern struct afs_addr_list *afs_yfsvl_get_endpoints(struct afs_net *, struct afs_addr_cursor *,
-						     struct key *, const uuid_t *);
+extern struct afs_addr_list *afs_yfsvl_get_endpoints(struct afs_vl_cursor *, const uuid_t *);
+
+/*
+ * vl_rotate.c
+ */
+extern bool afs_begin_vlserver_operation(struct afs_vl_cursor *,
+					 struct afs_cell *, struct key *);
+extern bool afs_select_vlserver(struct afs_vl_cursor *);
+extern bool afs_select_current_vlserver(struct afs_vl_cursor *);
+extern int afs_end_vlserver_operation(struct afs_vl_cursor *);
+
+/*
+ * vlserver_list.c
+ */
+static inline struct afs_vlserver *afs_get_vlserver(struct afs_vlserver *vlserver)
+{
+	atomic_inc(&vlserver->usage);
+	return vlserver;
+}
+
+static inline struct afs_vlserver_list *afs_get_vlserverlist(struct afs_vlserver_list *vllist)
+{
+	if (vllist)
+		atomic_inc(&vllist->usage);
+	return vllist;
+}
+
+extern struct afs_vlserver *afs_alloc_vlserver(const char *, size_t, unsigned short);
+extern void afs_put_vlserver(struct afs_net *, struct afs_vlserver *);
+extern struct afs_vlserver_list *afs_alloc_vlserver_list(unsigned int);
+extern void afs_put_vlserverlist(struct afs_net *, struct afs_vlserver_list *);
+extern struct afs_vlserver_list *afs_extract_vlserver_list(struct afs_cell *,
+							   const u8 *, size_t);
 
 /*
  * volume.c
diff --git a/fs/afs/proc.c b/fs/afs/proc.c
index 476dcbb79713..bcb6ef7af27d 100644
--- a/fs/afs/proc.c
+++ b/fs/afs/proc.c
@@ -253,56 +253,54 @@ static const struct seq_operations afs_proc_cell_volumes_ops = {
  */
 static int afs_proc_cell_vlservers_show(struct seq_file *m, void *v)
 {
-	struct sockaddr_rxrpc *addr = v;
+	struct afs_vlserver_entry *entry = v;
+	struct afs_vlserver *vlserver = entry->server;
+	struct afs_addr_list *alist = rcu_dereference(vlserver->addresses);
+	int i;
 
-	/* display header on line 1 */
-	if (v == (void *)1) {
-		seq_puts(m, "ADDRESS\n");
-		return 0;
+	seq_printf(m, "%s [p=%hu w=%hu]:\n",
+		   vlserver->name, entry->priority, entry->weight);
+	if (alist) {
+		for (i = 0; i < alist->nr_addrs; i++)
+			seq_printf(m, " %c %pISpc\n",
+				   alist->index == i ? '>' : '-',
+				   &alist->addrs[i].transport);
 	}
-
-	/* display one cell per line on subsequent lines */
-	seq_printf(m, "%pISp\n", &addr->transport);
 	return 0;
 }
 
 static void *afs_proc_cell_vlservers_start(struct seq_file *m, loff_t *_pos)
 	__acquires(rcu)
 {
-	struct afs_addr_list *alist;
+	struct afs_vlserver_list *vllist;
 	struct afs_cell *cell = PDE_DATA(file_inode(m->file));
 	loff_t pos = *_pos;
 
 	rcu_read_lock();
 
-	alist = rcu_dereference(cell->vl_addrs);
-
-	/* allow for the header line */
-	if (!pos)
-		return (void *) 1;
-	pos--;
-
-	if (!alist || pos >= alist->nr_addrs)
+	vllist = rcu_dereference(cell->vl_servers);
+	if (!vllist || pos >= vllist->nr_servers)
 		return NULL;
 
-	return alist->addrs + pos;
+	return &vllist->servers[pos];
 }
 
 static void *afs_proc_cell_vlservers_next(struct seq_file *m, void *v,
 					  loff_t *_pos)
 {
-	struct afs_addr_list *alist;
+	struct afs_vlserver_list *vllist;
 	struct afs_cell *cell = PDE_DATA(file_inode(m->file));
 	loff_t pos;
 
-	alist = rcu_dereference(cell->vl_addrs);
+	vllist = rcu_dereference(cell->vl_servers);
 
 	pos = *_pos;
-	(*_pos)++;
-	if (!alist || pos >= alist->nr_addrs)
+	pos++;
+	*_pos = pos;
+	if (!vllist || pos >= vllist->nr_servers)
 		return NULL;
 
-	return alist->addrs + pos;
+	return &vllist->servers[pos];
 }
 
 static void afs_proc_cell_vlservers_stop(struct seq_file *m, void *v)
diff --git a/fs/afs/server.c b/fs/afs/server.c
index 1d329e6981d5..6102ea9ee3fb 100644
--- a/fs/afs/server.c
+++ b/fs/afs/server.c
@@ -246,41 +246,23 @@ static struct afs_server *afs_alloc_server(struct afs_net *net,
 static struct afs_addr_list *afs_vl_lookup_addrs(struct afs_cell *cell,
 						 struct key *key, const uuid_t *uuid)
 {
-	struct afs_addr_cursor ac;
-	struct afs_addr_list *alist;
+	struct afs_vl_cursor vc;
+	struct afs_addr_list *alist = NULL;
 	int ret;
 
-	ret = afs_set_vl_cursor(&ac, cell);
-	if (ret < 0)
-		return ERR_PTR(ret);
-
-	while (afs_iterate_addresses(&ac)) {
-		if (test_bit(ac.index, &ac.alist->yfs))
-			alist = afs_yfsvl_get_endpoints(cell->net, &ac, key, uuid);
-		else
-			alist = afs_vl_get_addrs_u(cell->net, &ac, key, uuid);
-		switch (ac.error) {
-		case 0:
-			afs_end_cursor(&ac);
-			return alist;
-		case -ECONNABORTED:
-			ac.error = afs_abort_to_error(ac.abort_code);
-			goto error;
-		case -ENOMEM:
-		case -ENONET:
-			goto error;
-		case -ENETUNREACH:
-		case -EHOSTUNREACH:
-		case -ECONNREFUSED:
-			break;
-		default:
-			ac.error = -EIO;
-			goto error;
+	ret = -ERESTARTSYS;
+	if (afs_begin_vlserver_operation(&vc, cell, key)) {
+		while (afs_select_vlserver(&vc)) {
+			if (test_bit(vc.ac.index, &vc.ac.alist->yfs))
+				alist = afs_yfsvl_get_endpoints(&vc, uuid);
+			else
+				alist = afs_vl_get_addrs_u(&vc, uuid);
 		}
+
+		ret = afs_end_vlserver_operation(&vc);
 	}
 
-error:
-	return ERR_PTR(afs_end_cursor(&ac));
+	return ret < 0 ? ERR_PTR(ret) : alist;
 }
 
 /*
diff --git a/fs/afs/vl_list.c b/fs/afs/vl_list.c
new file mode 100644
index 000000000000..da421c24eba9
--- /dev/null
+++ b/fs/afs/vl_list.c
@@ -0,0 +1,289 @@
+/* AFS vlserver list management.
+ *
+ * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include "internal.h"
+
+struct afs_vlserver *afs_alloc_vlserver(const char *name, size_t name_len,
+					unsigned short port)
+{
+	struct afs_vlserver *vlserver;
+
+	vlserver = kzalloc(struct_size(vlserver, name, name_len + 1),
+			   GFP_KERNEL);
+	if (vlserver) {
+		atomic_set(&vlserver->usage, 1);
+		rwlock_init(&vlserver->lock);
+		vlserver->name_len = name_len;
+		vlserver->port = port;
+		memcpy(vlserver->name, name, name_len);
+	}
+	return vlserver;
+}
+
+void afs_put_vlserver(struct afs_net *net, struct afs_vlserver *vlserver)
+{
+	if (vlserver) {
+		unsigned int u = atomic_dec_return(&vlserver->usage);
+		//_debug("VL PUT %p{%u}", vlserver, u);
+
+		if (u == 0) {
+			afs_put_addrlist(vlserver->addresses);
+			kfree_rcu(vlserver, rcu);
+		}
+	}
+}
+
+struct afs_vlserver_list *afs_alloc_vlserver_list(unsigned int nr_servers)
+{
+	struct afs_vlserver_list *vllist;
+
+	vllist = kzalloc(struct_size(vllist, servers, nr_servers), GFP_KERNEL);
+	if (vllist) {
+		atomic_set(&vllist->usage, 1);
+		rwlock_init(&vllist->lock);
+	}
+
+	return vllist;
+}
+
+void afs_put_vlserverlist(struct afs_net *net, struct afs_vlserver_list *vllist)
+{
+	if (vllist) {
+		unsigned int u = atomic_dec_return(&vllist->usage);
+
+		//_debug("VLLS PUT %p{%u}", vllist, u);
+		if (u == 0) {
+			int i;
+
+			for (i = 0; i < vllist->nr_servers; i++) {
+				afs_put_vlserver(net, vllist->servers[i].server);
+			}
+			kfree_rcu(vllist, rcu);
+		}
+	}
+}
+
+u16 afs_extract_u16(const u8 **_b)
+{
+	u16 val;
+
+	val  = (u16)*(*_b)++ << 0;
+	val |= (u16)*(*_b)++ << 8;
+	return val;
+}
+
+/*
+ * Build a VL server address list from a DNS queried server list.
+ */
+struct afs_addr_list *afs_extract_vl_addrs(const u8 **_b, const u8 *end,
+					   u8 nr_addrs, u16 port)
+{
+	struct afs_addr_list *alist;
+	const u8 *b = *_b;
+	int ret = -EINVAL;
+
+	alist = afs_alloc_addrlist(nr_addrs, VL_SERVICE, port);
+	if (!alist)
+		return ERR_PTR(-ENOMEM);
+	if (nr_addrs == 0)
+		return alist;
+
+	for (; nr_addrs > 0 && end - b >= nr_addrs; nr_addrs--) {
+		__be32 x[4];
+		u8 family = *b++;
+
+		switch (family) {
+		case AF_INET:
+			if (end - b < 4)
+				goto error;
+			memcpy(x, b, 4);
+			afs_merge_fs_addr4(alist, x[0], port);
+			b += 4;
+			break;
+
+		case AF_INET6:
+			if (end - b < 16)
+				goto error;
+			memcpy(x, b, 16);
+			afs_merge_fs_addr6(alist, x, port);
+			b += 16;
+			break;
+
+		default:
+			ret = -EADDRNOTAVAIL;
+			goto error;
+		}
+	}
+
+	/* Start with IPv6 if available. */
+	if (alist->nr_ipv4 < alist->nr_addrs)
+		alist->index = alist->nr_ipv4;
+
+	*_b = b;
+	return alist;
+
+error:
+	afs_put_addrlist(alist);
+	return ERR_PTR(ret);
+}
+
+/*
+ * Build a VL server list from a DNS queried server list.
+ */
+struct afs_vlserver_list *afs_extract_vlserver_list(struct afs_cell *cell,
+						    const u8 *b, size_t b_size)
+{
+	struct afs_vlserver_list *vllist, *previous;
+	struct afs_addr_list *addrs;
+	struct afs_vlserver *server;
+	const u8 *end = b + b_size;
+	int ret = -ENOMEM, nr_servers, i, j;
+
+	_enter("");
+
+	/* Check that it's a server list, v1 */
+	if (b[0] != 0 || b[1] != 1 || end - b < 3) {
+		pr_notice("kAFS: Got DNS record [%u,%u] len %zu\n",
+			  b[0], b[1], end - b);
+		return ERR_PTR(-EDESTADDRREQ);
+	}
+	nr_servers = b[2];
+	b += 3;
+
+	vllist = afs_alloc_vlserver_list(nr_servers);
+	if (!vllist)
+		return ERR_PTR(-ENOMEM);
+
+	read_lock(&cell->vl_servers_lock);
+	previous = afs_get_vlserverlist(cell->vl_servers);
+	read_unlock(&cell->vl_servers_lock);
+
+	while (end - b >= 4 * 2 + 2 * 1) {
+		u16 name_len	= afs_extract_u16(&b);
+		u16 priority	= afs_extract_u16(&b);
+		u16 weight	= afs_extract_u16(&b);
+		u16 port	= afs_extract_u16(&b);
+		u8  protocol	= *b++;
+		u8  nr_addrs	= *b++;
+
+		if (end - b < name_len)
+			break;
+
+		_debug("extract %u %u %u %u %u %u %*.*s",
+		       name_len, priority, weight, port, protocol, nr_addrs,
+		       name_len, name_len, b);
+
+		ret = -EPROTONOSUPPORT;
+		if (protocol != IPPROTO_UDP)
+			goto error;
+		if (port == 0)
+			port = AFS_VL_PORT;
+
+		server = NULL;
+		if (previous) {
+			/* See if we can update an old server record */
+			for (i = 0; i < previous->nr_servers; i++) {
+				struct afs_vlserver *p = previous->servers[i].server;
+
+				if (p->name_len == name_len &&
+				    p->port == port &&
+				    strncasecmp(b, p->name, name_len) == 0) {
+					server = afs_get_vlserver(p);
+					break;
+				}
+			}
+		}
+
+		if (!server) {
+			ret = -ENOMEM;
+			server = afs_alloc_vlserver(b, name_len, port);
+			if (!server)
+				goto error;
+		}
+
+		b += name_len;
+
+		/* Extract the addresses - note that we can't skip this as we
+		 * have to advance the payload pointer.
+		 */
+		addrs = afs_extract_vl_addrs(&b, end, nr_addrs, port);
+		if (!addrs)
+			goto error_2;
+
+		if (vllist->nr_servers >= nr_servers) {
+			_debug("skip %u >= %u", vllist->nr_servers, nr_servers);
+			afs_put_addrlist(addrs);
+			afs_put_vlserver(cell->net, server);
+			continue;
+		}
+
+		if (addrs->nr_addrs == 0) {
+			afs_put_addrlist(addrs);
+			if (!rcu_access_pointer(server->addresses)) {
+				afs_put_vlserver(cell->net, server);
+				continue;
+			}
+		} else {
+			struct afs_addr_list *old = addrs;
+
+			write_lock(&server->lock);
+			rcu_swap_protected(server->addresses, old,
+					   lockdep_is_held(&server->lock));
+			write_unlock(&server->lock);
+			afs_put_addrlist(old);
+		}
+
+
+		/* TODO: Might want to check for duplicates */
+
+		/* Insertion-sort by priority and weight */
+		for (j = 0; j < vllist->nr_servers; j++) {
+			if (priority < vllist->servers[j].priority)
+				break; /* Lower preferable */
+			if (priority == vllist->servers[j].priority &&
+			    weight > vllist->servers[j].weight)
+				break; /* Higher preferable */
+		}
+
+		if (j < vllist->nr_servers) {
+			memmove(vllist->servers + j + 1,
+				vllist->servers + j,
+				(vllist->nr_servers - j) * sizeof(struct afs_vlserver_entry));
+		}
+
+		vllist->servers[j].priority = priority;
+		vllist->servers[j].weight = weight;
+		vllist->servers[j].server = server;
+		vllist->nr_servers++;
+	}
+
+	if (b != end) {
+		_debug("parse error %zd", b - end);
+		goto error;
+	}
+
+	ret = -EDESTADDRREQ;
+	if (vllist->nr_servers == 0)
+		goto error;
+
+	afs_put_vlserverlist(cell->net, previous);
+	_leave(" = ok [%u]", vllist->nr_servers);
+	return vllist;
+
+error_2:
+	afs_put_vlserver(cell->net, server);
+error:
+	afs_put_vlserverlist(cell->net, vllist);
+	afs_put_vlserverlist(cell->net, previous);
+	return ERR_PTR(ret);
+}
diff --git a/fs/afs/vl_rotate.c b/fs/afs/vl_rotate.c
new file mode 100644
index 000000000000..344118a85ec9
--- /dev/null
+++ b/fs/afs/vl_rotate.c
@@ -0,0 +1,239 @@
+/* Handle vlserver selection and rotation.
+ *
+ * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/sched/signal.h>
+#include "internal.h"
+#include "afs_vl.h"
+
+/*
+ * Begin an operation on a volume location server.
+ */
+bool afs_begin_vlserver_operation(struct afs_vl_cursor *vc, struct afs_cell *cell,
+				  struct key *key)
+{
+	memset(vc, 0, sizeof(*vc));
+	vc->cell = cell;
+	vc->key = key;
+	vc->ac.error = SHRT_MAX;
+
+	if (signal_pending(current)) {
+		vc->ac.error = -EINTR;
+		vc->flags |= AFS_VL_CURSOR_STOP;
+		return false;
+	}
+
+	return true;
+}
+
+/*
+ * Begin iteration through a server list, starting with the last used server if
+ * possible, or the last recorded good server if not.
+ */
+static bool afs_start_vl_iteration(struct afs_vl_cursor *vc)
+{
+	struct afs_cell *cell = vc->cell;
+
+	read_lock(&cell->vl_servers_lock);
+	vc->server_list = afs_get_vlserverlist(cell->vl_servers);
+	read_unlock(&cell->vl_servers_lock);
+	if (!vc->server_list)
+		return false;
+
+	vc->start = READ_ONCE(vc->server_list->index);
+	vc->index = vc->start;
+	return true;
+}
+
+/*
+ * Select the vlserver to use.  May be called multiple times to rotate
+ * through the vlservers.
+ */
+bool afs_select_vlserver(struct afs_vl_cursor *vc)
+{
+	struct afs_addr_list *alist;
+	struct afs_vlserver *vlserver;
+
+	_enter("%u/%u,%u/%u,%d,%d",
+	       vc->index, vc->start,
+	       vc->ac.index, vc->ac.start,
+	       vc->ac.error, vc->ac.abort_code);
+
+	if (vc->flags & AFS_VL_CURSOR_STOP) {
+		_leave(" = f [stopped]");
+		return false;
+	}
+
+	/* Evaluate the result of the previous operation, if there was one. */
+	switch (vc->ac.error) {
+	case SHRT_MAX:
+		goto start;
+
+	default:
+	case 0:
+		/* Success or local failure.  Stop. */
+		vc->flags |= AFS_VL_CURSOR_STOP;
+		_leave(" = f [okay/local %d]", vc->ac.error);
+		return false;
+
+	case -ECONNABORTED:
+		/* The far side rejected the operation on some grounds.  This
+		 * might involve the server being busy or the volume having been moved.
+		 */
+		switch (vc->ac.abort_code) {
+		case AFSVL_IO:
+		case AFSVL_BADVOLOPER:
+		case AFSVL_NOMEM:
+			/* The server went weird. */
+			vc->ac.error = -EREMOTEIO;
+			//write_lock(&vc->cell->vl_servers_lock);
+			//vc->server_list->weird_mask |= 1 << vc->index;
+			//write_unlock(&vc->cell->vl_servers_lock);
+			goto next_server;
+
+		default:
+			vc->ac.error = afs_abort_to_error(vc->ac.abort_code);
+			goto failed;
+		}
+
+	case -ENETUNREACH:
+	case -EHOSTUNREACH:
+	case -ECONNREFUSED:
+	case -ETIMEDOUT:
+	case -ETIME:
+		_debug("no conn");
+		goto iterate_address;
+
+	case -ECONNRESET:
+		_debug("call reset");
+		vc->flags |= AFS_VL_CURSOR_RETRY;
+		goto next_server;
+	}
+
+restart_from_beginning:
+	_debug("restart");
+	afs_end_cursor(&vc->ac);
+	afs_put_vlserverlist(vc->cell->net, vc->server_list);
+	vc->server_list = NULL;
+	if (vc->flags & AFS_VL_CURSOR_RETRIED)
+		goto failed;
+	vc->flags |= AFS_VL_CURSOR_RETRIED;
+start:
+	_debug("start");
+	/* TODO: Consider checking the VL server list */
+
+	if (!afs_start_vl_iteration(vc))
+		goto failed;
+
+use_server:
+	_debug("use");
+	/* We're starting on a different vlserver from the list.  We need to
+	 * check it, find its address list and probe its capabilities before we
+	 * use it.
+	 */
+	ASSERTCMP(vc->ac.alist, ==, NULL);
+	vlserver = vc->server_list->servers[vc->index].server;
+
+	// TODO: Check the vlserver occasionally
+	//if (!afs_check_vlserver_record(vc, vlserver))
+	//	goto failed;
+
+	_debug("USING VLSERVER: %s", vlserver->name);
+
+	read_lock(&vlserver->lock);
+	alist = rcu_dereference_protected(vlserver->addresses,
+					  lockdep_is_held(&vlserver->lock));
+	afs_get_addrlist(alist);
+	read_unlock(&vlserver->lock);
+
+	memset(&vc->ac, 0, sizeof(vc->ac));
+
+	/* Probe the current vlserver if we haven't done so yet. */
+#if 0 // TODO
+	if (!test_bit(AFS_VLSERVER_FL_PROBED, &vlserver->flags)) {
+		vc->ac.alist = afs_get_addrlist(alist);
+
+		if (!afs_probe_vlserver(vc)) {
+			switch (vc->ac.error) {
+			case -ENOMEM:
+			case -ERESTARTSYS:
+			case -EINTR:
+				goto failed;
+			default:
+				goto next_server;
+			}
+		}
+	}
+#endif
+
+	if (!vc->ac.alist)
+		vc->ac.alist = alist;
+	else
+		afs_put_addrlist(alist);
+
+	vc->ac.start = READ_ONCE(alist->index);
+	vc->ac.index = vc->ac.start;
+
+iterate_address:
+	ASSERT(vc->ac.alist);
+	_debug("iterate %d/%d", vc->ac.index, vc->ac.alist->nr_addrs);
+	/* Iterate over the current server's address list to try and find an
+	 * address on which it will respond to us.
+	 */
+	if (!afs_iterate_addresses(&vc->ac))
+		goto next_server;
+
+	_leave(" = t");
+	return true;
+
+next_server:
+	_debug("next");
+	afs_end_cursor(&vc->ac);
+	vc->index++;
+	if (vc->index >= vc->server_list->nr_servers)
+		vc->index = 0;
+	if (vc->index != vc->start)
+		goto use_server;
+
+	/* That's all the servers poked to no good effect.  Try again if some
+	 * of them were busy.
+	 */
+	if (vc->flags & AFS_VL_CURSOR_RETRY)
+		goto restart_from_beginning;
+
+	vc->ac.error = -EDESTADDRREQ;
+	goto failed;
+
+failed:
+	vc->flags |= AFS_VL_CURSOR_STOP;
+	afs_end_cursor(&vc->ac);
+	_leave(" = f [failed %d]", vc->ac.error);
+	return false;
+}
+
+/*
+ * Tidy up a volume location server cursor and unlock the vnode.
+ */
+int afs_end_vlserver_operation(struct afs_vl_cursor *vc)
+{
+	struct afs_net *net = vc->cell->net;
+	int ret;
+
+	afs_end_cursor(&vc->ac);
+	afs_put_vlserverlist(net, vc->server_list);
+
+	ret = vc->ac.error;
+	if (ret == -ECONNABORTED)
+		ret = afs_abort_to_error(vc->ac.abort_code);
+
+	return vc->ac.error;
+}
diff --git a/fs/afs/vlclient.c b/fs/afs/vlclient.c
index c3b740813fc7..75808b55af21 100644
--- a/fs/afs/vlclient.c
+++ b/fs/afs/vlclient.c
@@ -128,14 +128,13 @@ static const struct afs_call_type afs_RXVLGetEntryByNameU = {
  * Dispatch a get volume entry by name or ID operation (uuid variant).  If the
  * volname is a decimal number then it's a volume ID not a volume name.
  */
-struct afs_vldb_entry *afs_vl_get_entry_by_name_u(struct afs_net *net,
-						  struct afs_addr_cursor *ac,
-						  struct key *key,
+struct afs_vldb_entry *afs_vl_get_entry_by_name_u(struct afs_vl_cursor *vc,
 						  const char *volname,
 						  int volnamesz)
 {
 	struct afs_vldb_entry *entry;
 	struct afs_call *call;
+	struct afs_net *net = vc->cell->net;
 	size_t reqsz, padsz;
 	__be32 *bp;
 
@@ -155,7 +154,7 @@ struct afs_vldb_entry *afs_vl_get_entry_by_name_u(struct afs_net *net,
 		return ERR_PTR(-ENOMEM);
 	}
 
-	call->key = key;
+	call->key = vc->key;
 	call->reply[0] = entry;
 	call->ret_reply0 = true;
 
@@ -168,7 +167,7 @@ struct afs_vldb_entry *afs_vl_get_entry_by_name_u(struct afs_net *net,
 		memset((void *)bp + volnamesz, 0, padsz);
 
 	trace_afs_make_vl_call(call);
-	return (struct afs_vldb_entry *)afs_make_call(ac, call, GFP_KERNEL, false);
+	return (struct afs_vldb_entry *)afs_make_call(&vc->ac, call, GFP_KERNEL, false);
 }
 
 /*
@@ -267,14 +266,13 @@ static const struct afs_call_type afs_RXVLGetAddrsU = {
  * Dispatch an operation to get the addresses for a server, where the server is
  * nominated by UUID.
  */
-struct afs_addr_list *afs_vl_get_addrs_u(struct afs_net *net,
-					 struct afs_addr_cursor *ac,
-					 struct key *key,
+struct afs_addr_list *afs_vl_get_addrs_u(struct afs_vl_cursor *vc,
 					 const uuid_t *uuid)
 {
 	struct afs_ListAddrByAttributes__xdr *r;
 	const struct afs_uuid *u = (const struct afs_uuid *)uuid;
 	struct afs_call *call;
+	struct afs_net *net = vc->cell->net;
 	__be32 *bp;
 	int i;
 
@@ -286,7 +284,7 @@ struct afs_addr_list *afs_vl_get_addrs_u(struct afs_net *net,
 	if (!call)
 		return ERR_PTR(-ENOMEM);
 
-	call->key = key;
+	call->key = vc->key;
 	call->reply[0] = NULL;
 	call->ret_reply0 = true;
 
@@ -307,7 +305,7 @@ struct afs_addr_list *afs_vl_get_addrs_u(struct afs_net *net,
 		r->uuid.node[i] = htonl(u->node[i]);
 
 	trace_afs_make_vl_call(call);
-	return (struct afs_addr_list *)afs_make_call(ac, call, GFP_KERNEL, false);
+	return (struct afs_addr_list *)afs_make_call(&vc->ac, call, GFP_KERNEL, false);
 }
 
 /*
@@ -377,14 +375,13 @@ static const struct afs_call_type afs_RXVLGetCapabilities = {
 };
 
 /*
- * Probe a fileserver for the capabilities that it supports.  This can
+ * Probe a volume server for the capabilities that it supports.  This can
  * return up to 196 words.
  *
  * We use this to probe for service upgrade to determine what the server at the
  * other end supports.
  */
-int afs_vl_get_capabilities(struct afs_net *net,
-			    struct afs_addr_cursor *ac,
+int afs_vl_get_capabilities(struct afs_net *net, struct afs_addr_cursor *ac,
 			    struct key *key)
 {
 	struct afs_call *call;
@@ -619,12 +616,11 @@ static const struct afs_call_type afs_YFSVLGetEndpoints = {
  * Dispatch an operation to get the addresses for a server, where the server is
  * nominated by UUID.
  */
-struct afs_addr_list *afs_yfsvl_get_endpoints(struct afs_net *net,
-					      struct afs_addr_cursor *ac,
-					      struct key *key,
+struct afs_addr_list *afs_yfsvl_get_endpoints(struct afs_vl_cursor *vc,
 					      const uuid_t *uuid)
 {
 	struct afs_call *call;
+	struct afs_net *net = vc->cell->net;
 	__be32 *bp;
 
 	_enter("");
@@ -635,7 +631,7 @@ struct afs_addr_list *afs_yfsvl_get_endpoints(struct afs_net *net,
 	if (!call)
 		return ERR_PTR(-ENOMEM);
 
-	call->key = key;
+	call->key = vc->key;
 	call->reply[0] = NULL;
 	call->ret_reply0 = true;
 
@@ -646,5 +642,5 @@ struct afs_addr_list *afs_yfsvl_get_endpoints(struct afs_net *net,
 	memcpy(bp, uuid, sizeof(*uuid)); /* Type opr_uuid */
 
 	trace_afs_make_vl_call(call);
-	return (struct afs_addr_list *)afs_make_call(ac, call, GFP_KERNEL, false);
+	return (struct afs_addr_list *)afs_make_call(&vc->ac, call, GFP_KERNEL, false);
 }
diff --git a/fs/afs/volume.c b/fs/afs/volume.c
index 3037bd01f617..404b9de48dc4 100644
--- a/fs/afs/volume.c
+++ b/fs/afs/volume.c
@@ -74,55 +74,35 @@ static struct afs_vldb_entry *afs_vl_lookup_vldb(struct afs_cell *cell,
 						 const char *volname,
 						 size_t volnamesz)
 {
-	struct afs_addr_cursor ac;
-	struct afs_vldb_entry *vldb;
+	struct afs_vldb_entry *vldb = NULL;
+	struct afs_vl_cursor vc;
 	int ret;
 
-	ret = afs_set_vl_cursor(&ac, cell);
-	if (ret < 0)
-		return ERR_PTR(ret);
+	if (!afs_begin_vlserver_operation(&vc, cell, key))
+		return ERR_PTR(-ERESTARTSYS);
 
-	while (afs_iterate_addresses(&ac)) {
-		if (!test_bit(ac.index, &ac.alist->probed)) {
-			ret = afs_vl_get_capabilities(cell->net, &ac, key);
+	while (afs_select_vlserver(&vc)) {
+		if (!test_bit(vc.ac.index, &vc.ac.alist->probed)) {
+			ret = afs_vl_get_capabilities(cell->net, &vc.ac, key);
 			switch (ret) {
 			case VL_SERVICE:
-				clear_bit(ac.index, &ac.alist->yfs);
-				set_bit(ac.index, &ac.alist->probed);
-				ac.addr->srx_service = ret;
+				clear_bit(vc.ac.index, &vc.ac.alist->yfs);
+				set_bit(vc.ac.index, &vc.ac.alist->probed);
+				vc.ac.addr->srx_service = ret;
 				break;
 			case YFS_VL_SERVICE:
-				set_bit(ac.index, &ac.alist->yfs);
-				set_bit(ac.index, &ac.alist->probed);
-				ac.addr->srx_service = ret;
+				set_bit(vc.ac.index, &vc.ac.alist->yfs);
+				set_bit(vc.ac.index, &vc.ac.alist->probed);
+				vc.ac.addr->srx_service = ret;
 				break;
 			}
 		}
 		
-		vldb = afs_vl_get_entry_by_name_u(cell->net, &ac, key,
-						  volname, volnamesz);
-		switch (ac.error) {
-		case 0:
-			afs_end_cursor(&ac);
-			return vldb;
-		case -ECONNABORTED:
-			ac.error = afs_abort_to_error(ac.abort_code);
-			goto error;
-		case -ENOMEM:
-		case -ENONET:
-			goto error;
-		case -ENETUNREACH:
-		case -EHOSTUNREACH:
-		case -ECONNREFUSED:
-			break;
-		default:
-			ac.error = -EIO;
-			goto error;
-		}
+		vldb = afs_vl_get_entry_by_name_u(&vc, volname, volnamesz);
 	}
 
-error:
-	return ERR_PTR(afs_end_cursor(&ac));
+	ret = afs_end_vlserver_operation(&vc);
+	return ret < 0 ? ERR_PTR(ret) : vldb;
 }
 
 /*

[PATCH 5/6] afs: Always build address lists using the helper functions

[David Howells]

Make the address list string parser use the helper functions for adding
addresses to an address list so that they end up appropriately sorted.
This will better handles overruns and make them easier to compare.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/afs/addr_list.c |   32 +++++++++++++++-----------------
 1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/fs/afs/addr_list.c b/fs/afs/addr_list.c
index 630f91633b40..a7fdc05ba8d2 100644
--- a/fs/afs/addr_list.c
+++ b/fs/afs/addr_list.c
@@ -129,8 +129,10 @@ struct afs_vlserver_list *afs_parse_text_addrs(struct afs_net *net,
 	/* Extract the addresses */
 	p = text;
 	do {
-		struct sockaddr_rxrpc *srx = &alist->addrs[alist->nr_addrs];
 		const char *q, *stop;
+		unsigned int xport = port;
+		__be32 x[4];
+		int family;
 
 		if (*p == delim) {
 			p++;
@@ -146,19 +148,12 @@ struct afs_vlserver_list *afs_parse_text_addrs(struct afs_net *net,
 					break;
 		}
 
-		if (in4_pton(p, q - p,
-			     (u8 *)&srx->transport.sin6.sin6_addr.s6_addr32[3],
-			     -1, &stop)) {
-			srx->transport.sin6.sin6_addr.s6_addr32[0] = 0;
-			srx->transport.sin6.sin6_addr.s6_addr32[1] = 0;
-			srx->transport.sin6.sin6_addr.s6_addr32[2] = htonl(0xffff);
-		} else if (in6_pton(p, q - p,
-				    srx->transport.sin6.sin6_addr.s6_addr,
-				    -1, &stop)) {
-			/* Nothing to do */
-		} else {
+		if (in4_pton(p, q - p, (u8 *)&x[0], -1, &stop))
+			family = AF_INET;
+		else if (in6_pton(p, q - p, (u8 *)x, -1, &stop))
+			family = AF_INET6;
+		else
 			goto bad_address;
-		}
 
 		if (stop != q)
 			goto bad_address;
@@ -170,7 +165,7 @@ struct afs_vlserver_list *afs_parse_text_addrs(struct afs_net *net,
 		if (p < end) {
 			if (*p == '+') {
 				/* Port number specification "+1234" */
-				unsigned int xport = 0;
+				xport = 0;
 				p++;
 				if (p >= end || !isdigit(*p))
 					goto bad_address;
@@ -181,7 +176,6 @@ struct afs_vlserver_list *afs_parse_text_addrs(struct afs_net *net,
 						goto bad_address;
 					p++;
 				} while (p < end && isdigit(*p));
-				srx->transport.sin6.sin6_port = htons(xport);
 			} else if (*p == delim) {
 				p++;
 			} else {
@@ -189,8 +183,12 @@ struct afs_vlserver_list *afs_parse_text_addrs(struct afs_net *net,
 			}
 		}
 
-		alist->nr_addrs++;
-	} while (p < end && alist->nr_addrs < alist->max_addrs);
+		if (family == AF_INET)
+			afs_merge_fs_addr4(alist, x[0], xport);
+		else
+			afs_merge_fs_addr6(alist, x, xport);
+
+	} while (p < end);
 
 	_leave(" = [nr %u]", alist->nr_addrs);
 	return vllist;

[PATCH 6/6] afs: Sort address lists so that they are in logical ascending order

[David Howells]

Sort address lists so that they are in logical ascending order rather than
being partially in ascending order of the BE representations of those
values.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/afs/addr_list.c |   51 ++++++++++++++++++++++++---------------------------
 1 file changed, 24 insertions(+), 27 deletions(-)

diff --git a/fs/afs/addr_list.c b/fs/afs/addr_list.c
index a7fdc05ba8d2..99aa75aa5f07 100644
--- a/fs/afs/addr_list.c
+++ b/fs/afs/addr_list.c
@@ -251,22 +251,23 @@ struct afs_vlserver_list *afs_dns_query(struct afs_cell *cell, time64_t *_expiry
  */
 void afs_merge_fs_addr4(struct afs_addr_list *alist, __be32 xdr, u16 port)
 {
-	struct sockaddr_in6 *a;
-	__be16 xport = htons(port);
+	struct sockaddr_in6 *p;
+	u32 addr = ntohl(xdr);
 	int i;
 
 	if (alist->nr_addrs >= alist->max_addrs)
 		return;
 
 	for (i = 0; i < alist->nr_ipv4; i++) {
-		a = &alist->addrs[i].transport.sin6;
-		if (xdr == a->sin6_addr.s6_addr32[3] &&
-		    xport == a->sin6_port)
+		struct sockaddr_in6 *a = &alist->addrs[i].transport.sin6;
+		u32 a_addr = ntohl(a->sin6_addr.s6_addr32[3]);
+		u16 a_port = ntohs(a->sin6_port);
+
+		if (addr == a_addr && port == a_port)
 			return;
-		if (xdr == a->sin6_addr.s6_addr32[3] &&
-		    (u16 __force)xport < (u16 __force)a->sin6_port)
+		if (addr == a_addr && port < a_port)
 			break;
-		if ((u32 __force)xdr < (u32 __force)a->sin6_addr.s6_addr32[3])
+		if (addr < a_addr)
 			break;
 	}
 
@@ -275,12 +276,12 @@ void afs_merge_fs_addr4(struct afs_addr_list *alist, __be32 xdr, u16 port)
 			alist->addrs + i,
 			sizeof(alist->addrs[0]) * (alist->nr_addrs - i));
 
-	a = &alist->addrs[i].transport.sin6;
-	a->sin6_port		  = xport;
-	a->sin6_addr.s6_addr32[0] = 0;
-	a->sin6_addr.s6_addr32[1] = 0;
-	a->sin6_addr.s6_addr32[2] = htonl(0xffff);
-	a->sin6_addr.s6_addr32[3] = xdr;
+	p = &alist->addrs[i].transport.sin6;
+	p->sin6_port		  = htons(port);
+	p->sin6_addr.s6_addr32[0] = 0;
+	p->sin6_addr.s6_addr32[1] = 0;
+	p->sin6_addr.s6_addr32[2] = htonl(0xffff);
+	p->sin6_addr.s6_addr32[3] = xdr;
 	alist->nr_ipv4++;
 	alist->nr_addrs++;
 }
@@ -290,21 +291,20 @@ void afs_merge_fs_addr4(struct afs_addr_list *alist, __be32 xdr, u16 port)
  */
 void afs_merge_fs_addr6(struct afs_addr_list *alist, __be32 *xdr, u16 port)
 {
-	struct sockaddr_in6 *a;
-	__be16 xport = htons(port);
+	struct sockaddr_in6 *p;
 	int i, diff;
 
 	if (alist->nr_addrs >= alist->max_addrs)
 		return;
 
 	for (i = alist->nr_ipv4; i < alist->nr_addrs; i++) {
-		a = &alist->addrs[i].transport.sin6;
+		struct sockaddr_in6 *a = &alist->addrs[i].transport.sin6;
+		u16 a_port = ntohs(a->sin6_port);
+
 		diff = memcmp(xdr, &a->sin6_addr, 16);
-		if (diff == 0 &&
-		    xport == a->sin6_port)
+		if (diff == 0 && port == a_port)
 			return;
-		if (diff == 0 &&
-		    (u16 __force)xport < (u16 __force)a->sin6_port)
+		if (diff == 0 && port < a_port)
 			break;
 		if (diff < 0)
 			break;
@@ -315,12 +315,9 @@ void afs_merge_fs_addr6(struct afs_addr_list *alist, __be32 *xdr, u16 port)
 			alist->addrs + i,
 			sizeof(alist->addrs[0]) * (alist->nr_addrs - i));
 
-	a = &alist->addrs[i].transport.sin6;
-	a->sin6_port		  = xport;
-	a->sin6_addr.s6_addr32[0] = xdr[0];
-	a->sin6_addr.s6_addr32[1] = xdr[1];
-	a->sin6_addr.s6_addr32[2] = xdr[2];
-	a->sin6_addr.s6_addr32[3] = xdr[3];
+	p = &alist->addrs[i].transport.sin6;
+	p->sin6_port = htons(port);
+	memcpy(&p->sin6_addr, xdr, 16);
 	alist->nr_addrs++;
 }
 

Re: [PATCH 4/6] afs: Differentiate VL servers

[David Howells]

David Howells <dhowells@redhat.com> wrote:

> +		ret = -EPROTONOSUPPORT;
> +		if (protocol != IPPROTO_UDP)
> +			goto error;

This needs to be:

		ret = -EPROTONOSUPPORT;
		if (protocol != IPPROTO_UDP && protocol != 0)
			goto error;

so that if the protocol is unspecified by the DNS upcall program, we choose
UDP.

David