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afs: Implement VL server rotation

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Track VL servers as independent entities rather than lumping all their
addresses together into one set and implement server-level rotation 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.  This
     also displays the source and status of the data as indicated by the
     upcall.

Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells
2018-10-20 00:57:57 +01:00
parent e7f680f45b
commit 0a5143f2f8
11 changed files with 905 additions and 218 deletions
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37
fs/afs/cell.c
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@@ -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;
if (addresses) {
struct afs_vlserver_list *vllist;
alist = afs_parse_text_addrs(vllist, strlen(vllist), ':',
VL_SERVICE, AFS_VL_PORT);
if (IS_ERR(alist)) {
ret = PTR_ERR(alist);
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);