[PATCH v2 33/40] afs: Apply server breaks to mmap'd files in the call processor

David Howells
2023-12-13T13:51:05Z

Apply server breaks to mmap'd files that are being used from that server
from the call processor work function rather than punting it off to a
workqueue. The work item, afs_server_init_callback(), then bumps each
individual inode off to its own work item introducing a potentially lengthy
delay. This reduces that delay at the cost of extending the amount of time
we delay replying to the CB.InitCallBack3 notification RPC from the server.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
---
fs/afs/callback.c | 33 +++++++++++++++++++--------------
fs/afs/cell.c | 2 +-
fs/afs/internal.h | 4 +---
fs/afs/server.c | 2 --
fs/afs/server_list.c | 22 +++++++++++-----------
include/trace/events/afs.h | 2 ++
6 files changed, 34 insertions(+), 31 deletions(-)

diff --git a/fs/afs/callback.c b/fs/afs/callback.c
index 90f9b2a46ff4..f67e88076761 100644
--- a/fs/afs/callback.c
+++ b/fs/afs/callback.c
@@ -33,9 +33,8 @@ void afs_invalidate_mmap_work(struct work_struct *work)
unmap_mapping_pages(vnode->netfs.inode.i_mapping, 0, 0, false);
}

-void afs_server_init_callback_work(struct work_struct *work)
+static void afs_server_init_callback(struct afs_server *server)
{
- struct afs_server *server = container_of(work, struct afs_server, initcb_work);
struct afs_vnode *vnode;
struct afs_cell *cell = server->cell;

@@ -57,15 +56,19 @@ void afs_server_init_callback_work(struct work_struct *work)
*/
void afs_init_callback_state(struct afs_server *server)
{
- rcu_read_lock();
+ struct afs_cell *cell = server->cell;
+
+ down_read(&cell->vs_lock);
+
do {
server->cb_s_break++;
atomic_inc(&server->cell->fs_s_break);
if (!list_empty(&server->cell->fs_open_mmaps))
- queue_work(system_unbound_wq, &server->initcb_work);
+ afs_server_init_callback(server);

} while ((server = rcu_dereference(server->uuid_next)));
- rcu_read_unlock();
+
+ up_read(&cell->vs_lock);
}

/*
@@ -112,7 +115,7 @@ static struct afs_volume *afs_lookup_volume_rcu(struct afs_cell *cell,
struct rb_node *p;
int seq = 1;

- do {
+ for (;;) {
/* Unfortunately, rbtree walking doesn't give reliable results
* under just the RCU read lock, so we have to check for
* changes.
@@ -133,7 +136,12 @@ static struct afs_volume *afs_lookup_volume_rcu(struct afs_cell *cell,
volume = NULL;
}

- } while (need_seqretry(&cell->volume_lock, seq));
+ if (volume && afs_try_get_volume(volume, afs_volume_trace_get_callback))
+ break;
+ if (!need_seqretry(&cell->volume_lock, seq))
+ break;
+ seq |= 1; /* Want a lock next time */
+ }

done_seqretry(&cell->volume_lock, seq);
return volume;
@@ -188,12 +196,11 @@ static void afs_break_some_callbacks(struct afs_server *server,
afs_volid_t vid = cbb->fid.vid;
size_t i;

+ rcu_read_lock();
volume = afs_lookup_volume_rcu(server->cell, vid);
-
/* TODO: Find all matching volumes if we couldn't match the server and
* break them anyway.
*/
-
for (i = *_count; i > 0; cbb++, i--) {
if (cbb->fid.vid == vid) {
_debug("- Fid { vl=%08llx n=%llu u=%u }",
@@ -207,6 +214,9 @@ static void afs_break_some_callbacks(struct afs_server *server,
*residue++ = *cbb;
}
}
+
+ rcu_read_unlock();
+ afs_put_volume(volume, afs_volume_trace_put_callback);
}

/*
@@ -219,11 +229,6 @@ void afs_break_callbacks(struct afs_server *server, size_t count,

ASSERT(server != NULL);

- rcu_read_lock();
-
while (count > 0)
afs_break_some_callbacks(server, callbacks, &count);
-
- rcu_read_unlock();
- return;
}
diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index 6b389f2bcd0c..1e5cb0f6ee07 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -161,7 +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);
+ init_rwsem(&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 4a3d946b1d2a..5ae4ca999d65 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -414,7 +414,7 @@ struct afs_cell {
unsigned int debug_id;

/* The volumes belonging to this cell */
- spinlock_t vs_lock; /* Lock for server->volumes */
+ struct rw_semaphore 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 */
@@ -566,7 +566,6 @@ struct afs_server {
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 */
unsigned long flags;
@@ -1041,7 +1040,6 @@ void afs_get_address_preferences(struct afs_net *net, struct afs_addr_list *alis
* callback.c
*/
extern void afs_invalidate_mmap_work(struct work_struct *);
-extern void afs_server_init_callback_work(struct work_struct *work);
extern void afs_init_callback_state(struct afs_server *);
extern void __afs_break_callback(struct afs_vnode *, enum afs_cb_break_reason);
extern void afs_break_callback(struct afs_vnode *, enum afs_cb_break_reason);
diff --git a/fs/afs/server.c b/fs/afs/server.c
index db2f66b11b40..e169121f603e 100644
--- a/fs/afs/server.c
+++ b/fs/afs/server.c
@@ -218,7 +218,6 @@ static struct afs_server *afs_alloc_server(struct afs_cell *cell,
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);
spin_lock_init(&server->probe_lock);
@@ -470,7 +469,6 @@ static void afs_destroy_server(struct afs_net *net, struct afs_server *server)
if (test_bit(AFS_SERVER_FL_MAY_HAVE_CB, &server->flags))
afs_give_up_callbacks(net, server);

- flush_work(&server->initcb_work);
afs_put_server(net, server, afs_server_trace_destroy);
}

diff --git a/fs/afs/server_list.c b/fs/afs/server_list.c
index 4d6369477f54..cfd900eb09ed 100644
--- a/fs/afs/server_list.c
+++ b/fs/afs/server_list.c
@@ -136,7 +136,7 @@ void afs_attach_volume_to_servers(struct afs_volume *volume, struct afs_server_l
struct list_head *p;
unsigned int i;

- spin_lock(&volume->cell->vs_lock);
+ down_write(&volume->cell->vs_lock);

for (i = 0; i < slist->nr_servers; i++) {
se = &slist->servers[i];
@@ -147,11 +147,11 @@ void afs_attach_volume_to_servers(struct afs_volume *volume, struct afs_server_l
if (volume->vid <= pe->volume->vid)
break;
}
- list_add_tail_rcu(&se->slink, p);
+ list_add_tail(&se->slink, p);
}

slist->attached = true;
- spin_unlock(&volume->cell->vs_lock);
+ up_write(&volume->cell->vs_lock);
}

/*
@@ -164,7 +164,7 @@ void afs_reattach_volume_to_servers(struct afs_volume *volume, struct afs_server
{
unsigned int n = 0, o = 0;

- spin_lock(&volume->cell->vs_lock);
+ down_write(&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;
@@ -174,7 +174,7 @@ void afs_reattach_volume_to_servers(struct afs_volume *volume, struct afs_server
int diff;

if (pn && po && pn->server == po->server) {
- list_replace_rcu(&po->slink, &pn->slink);
+ list_replace(&po->slink, &pn->slink);
n++;
o++;
continue;
@@ -192,15 +192,15 @@ void afs_reattach_volume_to_servers(struct afs_volume *volume, struct afs_server
if (volume->vid <= s->volume->vid)
break;
}
- list_add_tail_rcu(&pn->slink, p);
+ list_add_tail(&pn->slink, p);
n++;
} else {
- list_del_rcu(&po->slink);
+ list_del(&po->slink);
o++;
}
}

- spin_unlock(&volume->cell->vs_lock);
+ up_write(&volume->cell->vs_lock);
}

/*
@@ -213,11 +213,11 @@ void afs_detach_volume_from_servers(struct afs_volume *volume, struct afs_server
if (!slist->attached)
return;

- spin_lock(&volume->cell->vs_lock);
+ down_write(&volume->cell->vs_lock);

for (i = 0; i < slist->nr_servers; i++)
- list_del_rcu(&slist->servers[i].slink);
+ list_del(&slist->servers[i].slink);

slist->attached = false;
- spin_unlock(&volume->cell->vs_lock);
+ up_write(&volume->cell->vs_lock);
}
diff --git a/include/trace/events/afs.h b/include/trace/events/afs.h
index cf2fa4fddd5b..63ab23876be8 100644
--- a/include/trace/events/afs.h
+++ b/include/trace/events/afs.h
@@ -151,9 +151,11 @@ enum yfs_cm_operation {
EM(afs_volume_trace_alloc, "ALLOC ") \
EM(afs_volume_trace_free, "FREE ") \
EM(afs_volume_trace_get_alloc_sbi, "GET sbi-alloc ") \
+ EM(afs_volume_trace_get_callback, "GET callback ") \
EM(afs_volume_trace_get_cell_insert, "GET cell-insrt") \
EM(afs_volume_trace_get_new_op, "GET op-new ") \
EM(afs_volume_trace_get_query_alias, "GET cell-alias") \
+ EM(afs_volume_trace_put_callback, "PUT callback ") \
EM(afs_volume_trace_put_cell_dup, "PUT cell-dup ") \
EM(afs_volume_trace_put_cell_root, "PUT cell-root ") \
EM(afs_volume_trace_put_destroy_sbi, "PUT sbi-destry") \