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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>
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David Howells committed Oct 23, 2018
1 parent e7f680f commit 0a5143f
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Showing 11 changed files with 905 additions and 218 deletions.
2 changes: 2 additions & 0 deletions fs/afs/Makefile
View file
Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,8 @@ kafs-y := \
super.o \
netdevices.o \
vlclient.o \
vl_rotate.o \
vl_list.o \
volume.o \
write.o \
xattr.o
Expand Down
163 changes: 84 additions & 79 deletions fs/afs/addr_list.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -64,38 +64,50 @@ 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;
const char *problem;
unsigned int nr = 0;
int ret = -ENOMEM;

_enter("%*.*s,%c", (int)len, (int)len, text, delim);

if (!len)
if (!len) {
_leave(" = -EDESTADDRREQ [empty]");
return ERR_PTR(-EDESTADDRREQ);
}

if (delim == ':' && (memchr(text, ',', len) || !memchr(text, '.', len)))
delim = ',';

/* Count the addresses */
p = text;
do {
if (!*p)
return ERR_PTR(-EINVAL);
if (!*p) {
problem = "nul";
goto inval;
}
if (*p == delim)
continue;
nr++;
if (*p == '[') {
p++;
if (p == end)
return ERR_PTR(-EINVAL);
if (p == end) {
problem = "brace1";
goto inval;
}
p = memchr(p, ']', end - p);
if (!p)
return ERR_PTR(-EINVAL);
if (!p) {
problem = "brace2";
goto inval;
}
p++;
if (p >= end)
break;
Expand All @@ -109,10 +121,19 @@ 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_vl;

alist = afs_alloc_addrlist(nr, service, AFS_VL_PORT);
if (!alist)
goto error;

/* Extract the addresses */
p = text;
do {
Expand All @@ -135,17 +156,21 @@ struct afs_addr_list *afs_parse_text_addrs(const char *text, size_t len,
break;
}

if (in4_pton(p, q - p, (u8 *)&x[0], -1, &stop))
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))
} else if (in6_pton(p, q - p, (u8 *)x, -1, &stop)) {
family = AF_INET6;
else
} else {
problem = "family";
goto bad_address;
}

if (stop != q)
p = q;
if (stop != p) {
problem = "nostop";
goto bad_address;
}

p = q;
if (q < end && *q == ']')
p++;

Expand All @@ -154,18 +179,23 @@ struct afs_addr_list *afs_parse_text_addrs(const char *text, size_t len,
/* Port number specification "+1234" */
xport = 0;
p++;
if (p >= end || !isdigit(*p))
if (p >= end || !isdigit(*p)) {
problem = "port";
goto bad_address;
}
do {
xport *= 10;
xport += *p - '0';
if (xport > 65535)
if (xport > 65535) {
problem = "pval";
goto bad_address;
}
p++;
} while (p < end && isdigit(*p));
} else if (*p == delim) {
p++;
} else {
problem = "weird";
goto bad_address;
}
}
Expand All @@ -177,12 +207,23 @@ struct afs_addr_list *afs_parse_text_addrs(const char *text, size_t len,

} while (p < end);

rcu_assign_pointer(vllist->servers[0].server->addresses, alist);
_leave(" = [nr %u]", alist->nr_addrs);
return alist;
return vllist;

bad_address:
kfree(alist);
inval:
_leave(" = -EINVAL [%s %zu %*.*s]",
problem, p - text, (int)len, (int)len, text);
return ERR_PTR(-EINVAL);
bad_address:
_leave(" = -EINVAL [%s %zu %*.*s]",
problem, p - text, (int)len, (int)len, text);
ret = -EINVAL;
error:
afs_put_addrlist(alist);
error_vl:
afs_put_vlserverlist(net, vllist);
return ERR_PTR(ret);
}

/*
Expand All @@ -201,30 +242,34 @@ 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) {
_leave(" = %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 %ld\n", PTR_ERR(vllist));

return vllist;
}

/*
Expand Down Expand Up @@ -347,43 +392,3 @@ 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;
}
39 changes: 20 additions & 19 deletions fs/afs/cell.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand All @@ -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) {
Expand All @@ -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;
}

Expand Down Expand Up @@ -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);
Expand All @@ -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))
Expand All @@ -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);

Expand Down
2 changes: 1 addition & 1 deletion fs/afs/dynroot.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down
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