[PATCH v2 30/40] afs: Make it possible to find the volumes that are using a server

David Howells
2023-12-13T13:50:57Z

Make it possible to find the afs_volume structs that are using an
afs_server struct to aid in breaking volume callbacks.

The way this is done is that each afs_volume already has an array of
afs_server_entry records that point to the servers where that volume might
be found. An afs_volume backpointer and a list node is added to each entry
and each entry is then added to an RCU-traversable list on the afs_server
to which it points.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
---
fs/afs/cell.c | 1 +
fs/afs/internal.h | 23 +++++----
fs/afs/server.c | 1 +
fs/afs/server_list.c | 112 +++++++++++++++++++++++++++++++++++++++----
fs/afs/vl_alias.c | 2 +-
fs/afs/volume.c | 36 ++++++++------
6 files changed, 143 insertions(+), 32 deletions(-)

diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index 988c2ac7cece..69716fc0ee36 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -161,6 +161,7 @@ static struct afs_cell *afs_alloc_cell(struct afs_net *net,
refcount_set(&cell->ref, 1);
atomic_set(&cell->active, 0);
INIT_WORK(&cell->manager, afs_manage_cell_work);
+ spin_lock_init(&cell->vs_lock);
cell->volumes = RB_ROOT;
INIT_HLIST_HEAD(&cell->proc_volumes);
seqlock_init(&cell->volume_lock);
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 96c1074fe78d..0b726bd2cf8c 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -414,6 +414,7 @@ struct afs_cell {
unsigned int debug_id;

/* The volumes belonging to this cell */
+ spinlock_t vs_lock; /* Lock for server->volumes */
struct rb_root volumes; /* Tree of volumes on this server */
struct hlist_head proc_volumes; /* procfs volume list */
seqlock_t volume_lock; /* For volumes */
@@ -564,6 +565,7 @@ struct afs_server {
struct hlist_node addr4_link; /* Link in net->fs_addresses4 */
struct hlist_node addr6_link; /* Link in net->fs_addresses6 */
struct hlist_node proc_link; /* Link in net->fs_proc */
+ struct list_head volumes; /* RCU list of afs_server_entry objects */
struct work_struct initcb_work; /* Work for CB.InitCallBackState* */
struct afs_server *gc_next; /* Next server in manager's list */
time64_t unuse_time; /* Time at which last unused */
@@ -605,12 +607,14 @@ struct afs_server {
*/
struct afs_server_entry {
struct afs_server *server;
+ struct afs_volume *volume;
+ struct list_head slink; /* Link in server->volumes */
};

struct afs_server_list {
struct rcu_head rcu;
- afs_volid_t vids[AFS_MAXTYPES]; /* Volume IDs */
refcount_t usage;
+ bool attached; /* T if attached to servers */
unsigned char nr_servers;
unsigned char preferred; /* Preferred server */
unsigned short vnovol_mask; /* Servers to be skipped due to VNOVOL */
@@ -623,10 +627,9 @@ struct afs_server_list {
* Live AFS volume management.
*/
struct afs_volume {
- union {
- struct rcu_head rcu;
- afs_volid_t vid; /* volume ID */
- };
+ struct rcu_head rcu;
+ afs_volid_t vid; /* The volume ID of this volume */
+ afs_volid_t vids[AFS_MAXTYPES]; /* All associated volume IDs */
refcount_t ref;
time64_t update_at; /* Time at which to next update */
struct afs_cell *cell; /* Cell to which belongs (pins ref) */
@@ -1528,10 +1531,14 @@ static inline struct afs_server_list *afs_get_serverlist(struct afs_server_list
}

extern void afs_put_serverlist(struct afs_net *, struct afs_server_list *);
-extern struct afs_server_list *afs_alloc_server_list(struct afs_cell *, struct key *,
- struct afs_vldb_entry *,
- u8);
+struct afs_server_list *afs_alloc_server_list(struct afs_volume *volume,
+ struct key *key,
+ struct afs_vldb_entry *vldb);
extern bool afs_annotate_server_list(struct afs_server_list *, struct afs_server_list *);
+void afs_attach_volume_to_servers(struct afs_volume *volume, struct afs_server_list *slist);
+void afs_reattach_volume_to_servers(struct afs_volume *volume, struct afs_server_list *slist,
+ struct afs_server_list *old);
+void afs_detach_volume_from_servers(struct afs_volume *volume, struct afs_server_list *slist);

/*
* super.c
diff --git a/fs/afs/server.c b/fs/afs/server.c
index 281625c71aff..db2f66b11b40 100644
--- a/fs/afs/server.c
+++ b/fs/afs/server.c
@@ -217,6 +217,7 @@ static struct afs_server *afs_alloc_server(struct afs_cell *cell,
server->addr_version = alist->version;
server->uuid = *uuid;
rwlock_init(&server->fs_lock);
+ INIT_LIST_HEAD(&server->volumes);
INIT_WORK(&server->initcb_work, afs_server_init_callback_work);
init_waitqueue_head(&server->probe_wq);
INIT_LIST_HEAD(&server->probe_link);
diff --git a/fs/afs/server_list.c b/fs/afs/server_list.c
index b59896b1de0a..4d6369477f54 100644
--- a/fs/afs/server_list.c
+++ b/fs/afs/server_list.c
@@ -24,13 +24,13 @@ void afs_put_serverlist(struct afs_net *net, struct afs_server_list *slist)
/*
* Build a server list from a VLDB record.
*/
-struct afs_server_list *afs_alloc_server_list(struct afs_cell *cell,
+struct afs_server_list *afs_alloc_server_list(struct afs_volume *volume,
struct key *key,
- struct afs_vldb_entry *vldb,
- u8 type_mask)
+ struct afs_vldb_entry *vldb)
{
struct afs_server_list *slist;
struct afs_server *server;
+ unsigned int type_mask = 1 << volume->type;
int ret = -ENOMEM, nr_servers = 0, i, j;

for (i = 0; i < vldb->nr_servers; i++)
@@ -44,15 +44,12 @@ struct afs_server_list *afs_alloc_server_list(struct afs_cell *cell,
refcount_set(&slist->usage, 1);
rwlock_init(&slist->lock);

- for (i = 0; i < AFS_MAXTYPES; i++)
- slist->vids[i] = vldb->vid[i];
-
/* Make sure a records exists for each server in the list. */
for (i = 0; i < vldb->nr_servers; i++) {
if (!(vldb->fs_mask[i] & type_mask))
continue;

- server = afs_lookup_server(cell, key, &vldb->fs_server[i],
+ server = afs_lookup_server(volume->cell, key, &vldb->fs_server[i],
vldb->addr_version[i]);
if (IS_ERR(server)) {
ret = PTR_ERR(server);
@@ -70,7 +67,7 @@ struct afs_server_list *afs_alloc_server_list(struct afs_cell *cell,
break;
if (j < slist->nr_servers) {
if (slist->servers[j].server == server) {
- afs_put_server(cell->net, server,
+ afs_put_server(volume->cell->net, server,
afs_server_trace_put_slist_isort);
continue;
}
@@ -81,6 +78,7 @@ struct afs_server_list *afs_alloc_server_list(struct afs_cell *cell,
}

slist->servers[j].server = server;
+ slist->servers[j].volume = volume;
slist->nr_servers++;
}

@@ -92,7 +90,7 @@ struct afs_server_list *afs_alloc_server_list(struct afs_cell *cell,
return slist;

error_2:
- afs_put_serverlist(cell->net, slist);
+ afs_put_serverlist(volume->cell->net, slist);
error:
return ERR_PTR(ret);
}
@@ -127,3 +125,99 @@ bool afs_annotate_server_list(struct afs_server_list *new,

return true;
}
+
+/*
+ * Attach a volume to the servers it is going to use.
+ */
+void afs_attach_volume_to_servers(struct afs_volume *volume, struct afs_server_list *slist)
+{
+ struct afs_server_entry *se, *pe;
+ struct afs_server *server;
+ struct list_head *p;
+ unsigned int i;
+
+ spin_lock(&volume->cell->vs_lock);
+
+ for (i = 0; i < slist->nr_servers; i++) {
+ se = &slist->servers[i];
+ server = se->server;
+
+ list_for_each(p, &server->volumes) {
+ pe = list_entry(p, struct afs_server_entry, slink);
+ if (volume->vid <= pe->volume->vid)
+ break;
+ }
+ list_add_tail_rcu(&se->slink, p);
+ }
+
+ slist->attached = true;
+ spin_unlock(&volume->cell->vs_lock);
+}
+
+/*
+ * Reattach a volume to the servers it is going to use when server list is
+ * replaced. We try to switch the attachment points to avoid rewalking the
+ * lists.
+ */
+void afs_reattach_volume_to_servers(struct afs_volume *volume, struct afs_server_list *new,
+ struct afs_server_list *old)
+{
+ unsigned int n = 0, o = 0;
+
+ spin_lock(&volume->cell->vs_lock);
+
+ while (n < new->nr_servers || o < old->nr_servers) {
+ struct afs_server_entry *pn = n < new->nr_servers ? &new->servers[n] : NULL;
+ struct afs_server_entry *po = o < old->nr_servers ? &old->servers[o] : NULL;
+ struct afs_server_entry *s;
+ struct list_head *p;
+ int diff;
+
+ if (pn && po && pn->server == po->server) {
+ list_replace_rcu(&po->slink, &pn->slink);
+ n++;
+ o++;
+ continue;
+ }
+
+ if (pn && po)
+ diff = memcmp(&pn->server->uuid, &po->server->uuid,
+ sizeof(pn->server->uuid));
+ else
+ diff = pn ? -1 : 1;
+
+ if (diff < 0) {
+ list_for_each(p, &pn->server->volumes) {
+ s = list_entry(p, struct afs_server_entry, slink);
+ if (volume->vid <= s->volume->vid)
+ break;
+ }
+ list_add_tail_rcu(&pn->slink, p);
+ n++;
+ } else {
+ list_del_rcu(&po->slink);
+ o++;
+ }
+ }
+
+ spin_unlock(&volume->cell->vs_lock);
+}
+
+/*
+ * Detach a volume from the servers it has been using.
+ */
+void afs_detach_volume_from_servers(struct afs_volume *volume, struct afs_server_list *slist)
+{
+ unsigned int i;
+
+ if (!slist->attached)
+ return;
+
+ spin_lock(&volume->cell->vs_lock);
+
+ for (i = 0; i < slist->nr_servers; i++)
+ list_del_rcu(&slist->servers[i].slink);
+
+ slist->attached = false;
+ spin_unlock(&volume->cell->vs_lock);
+}
diff --git a/fs/afs/vl_alias.c b/fs/afs/vl_alias.c
index 43788d0c18e8..63e7ed324af9 100644
--- a/fs/afs/vl_alias.c
+++ b/fs/afs/vl_alias.c
@@ -77,7 +77,7 @@ static int afs_compare_volume_slists(const struct afs_volume *vol_a,
lb = rcu_dereference(vol_b->servers);

for (i = 0; i < AFS_MAXTYPES; i++)
- if (la->vids[i] != lb->vids[i])
+ if (vol_a->vids[i] != vol_b->vids[i])
return 0;

while (a < la->nr_servers && b < lb->nr_servers) {
diff --git a/fs/afs/volume.c b/fs/afs/volume.c
index 115c081a8e2c..aefb982dee9a 100644
--- a/fs/afs/volume.c
+++ b/fs/afs/volume.c
@@ -72,11 +72,11 @@ static void afs_remove_volume_from_cell(struct afs_volume *volume)
*/
static struct afs_volume *afs_alloc_volume(struct afs_fs_context *params,
struct afs_vldb_entry *vldb,
- unsigned long type_mask)
+ struct afs_server_list **_slist)
{
struct afs_server_list *slist;
struct afs_volume *volume;
- int ret = -ENOMEM;
+ int ret = -ENOMEM, i;

volume = kzalloc(sizeof(struct afs_volume), GFP_KERNEL);
if (!volume)
@@ -95,13 +95,16 @@ static struct afs_volume *afs_alloc_volume(struct afs_fs_context *params,
rwlock_init(&volume->cb_v_break_lock);
memcpy(volume->name, vldb->name, vldb->name_len + 1);

- slist = afs_alloc_server_list(params->cell, params->key, vldb, type_mask);
+ for (i = 0; i < AFS_MAXTYPES; i++)
+ volume->vids[i] = vldb->vid[i];
+
+ slist = afs_alloc_server_list(volume, params->key, vldb);
if (IS_ERR(slist)) {
ret = PTR_ERR(slist);
goto error_1;
}

- refcount_set(&slist->usage, 1);
+ *_slist = slist;
rcu_assign_pointer(volume->servers, slist);
trace_afs_volume(volume->vid, 1, afs_volume_trace_alloc);
return volume;
@@ -117,17 +120,19 @@ static struct afs_volume *afs_alloc_volume(struct afs_fs_context *params,
* Look up or allocate a volume record.
*/
static struct afs_volume *afs_lookup_volume(struct afs_fs_context *params,
- struct afs_vldb_entry *vldb,
- unsigned long type_mask)
+ struct afs_vldb_entry *vldb)
{
+ struct afs_server_list *slist;
struct afs_volume *candidate, *volume;

- candidate = afs_alloc_volume(params, vldb, type_mask);
+ candidate = afs_alloc_volume(params, vldb, &slist);
if (IS_ERR(candidate))
return candidate;

volume = afs_insert_volume_into_cell(params->cell, candidate);
- if (volume != candidate)
+ if (volume == candidate)
+ afs_attach_volume_to_servers(volume, slist);
+ else
afs_put_volume(params->net, candidate, afs_volume_trace_put_cell_dup);
return volume;
}
@@ -208,8 +213,7 @@ struct afs_volume *afs_create_volume(struct afs_fs_context *params)
goto error;
}

- type_mask = 1UL << params->type;
- volume = afs_lookup_volume(params, vldb, type_mask);
+ volume = afs_lookup_volume(params, vldb);

error:
kfree(vldb);
@@ -221,14 +225,17 @@ struct afs_volume *afs_create_volume(struct afs_fs_context *params)
*/
static void afs_destroy_volume(struct afs_net *net, struct afs_volume *volume)
{
+ struct afs_server_list *slist = rcu_access_pointer(volume->servers);
+
_enter("%p", volume);

#ifdef CONFIG_AFS_FSCACHE
ASSERTCMP(volume->cache, ==, NULL);
#endif

+ afs_detach_volume_from_servers(volume, slist);
afs_remove_volume_from_cell(volume);
- afs_put_serverlist(net, rcu_access_pointer(volume->servers));
+ afs_put_serverlist(net, slist);
afs_put_cell(volume->cell, afs_cell_trace_put_vol);
trace_afs_volume(volume->vid, refcount_read(&volume->ref),
afs_volume_trace_free);
@@ -362,8 +369,7 @@ static int afs_update_volume_status(struct afs_volume *volume, struct key *key)
}

/* See if the volume's server list got updated. */
- new = afs_alloc_server_list(volume->cell, key,
- vldb, (1 << volume->type));
+ new = afs_alloc_server_list(volume, key, vldb);
if (IS_ERR(new)) {
ret = PTR_ERR(new);
goto error_vldb;
@@ -384,9 +390,11 @@ static int afs_update_volume_status(struct afs_volume *volume, struct key *key)

volume->update_at = ktime_get_real_seconds() + afs_volume_record_life;
write_unlock(&volume->servers_lock);
- ret = 0;

+ if (discard == old)
+ afs_reattach_volume_to_servers(volume, new, old);
afs_put_serverlist(volume->cell->net, discard);
+ ret = 0;
error_vldb:
kfree(vldb);