afs: Give an afs_server object a ref on the afs_cell object it points to

[ Upstream commit 1f0fc3374f3345ff1d150c5c56ac5016e5d3826a ]

Give an afs_server object a ref on the afs_cell object it points to so that
the cell doesn't get deleted before the server record.

Whilst this is circular (cell -> vol -> server_list -> server -> cell), the
ref only pins the memory, not the lifetime as that's controlled by the
activity counter.  When the volume's activity counter reaches 0, it
detaches from the cell and discards its server list; when a cell's activity
counter reaches 0, it discards its root volume.  At that point, the
circularity is cut.

Fixes: d2ddc776a458 ("afs: Overhaul volume and server record caching and fileserver rotation")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Simon Horman <horms@kernel.org>
cc: linux-afs@lists.infradead.org
Link: https://patch.msgid.link/20250218192250.296870-6-dhowells@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/afs/server.c b/fs/afs/server.c
index 038f9d0ae3af8ee1df24dc163c972e826c5d62fb..4504e16b458cc1153db19f5a310e10afc6a186c6 100644 (file)
--- a/fs/afs/server.c
+++ b/fs/afs/server.c
@@ -163,6 +163,8 @@ static struct afs_server *afs_install_server(struct afs_cell *cell,
        rb_insert_color(&server->uuid_rb, &net->fs_servers);
        hlist_add_head_rcu(&server->proc_link, &net->fs_proc);
 
+       afs_get_cell(cell, afs_cell_trace_get_server);
+
 added_dup:
        write_seqlock(&net->fs_addr_lock);
        estate = rcu_dereference_protected(server->endpoint_state,
@@ -442,6 +444,7 @@ static void afs_server_rcu(struct rcu_head *rcu)
                         atomic_read(&server->active), afs_server_trace_free);
        afs_put_endpoint_state(rcu_access_pointer(server->endpoint_state),
                               afs_estate_trace_put_server);
+       afs_put_cell(server->cell, afs_cell_trace_put_server);
        kfree(server);
 }
 

diff --git a/include/trace/events/afs.h b/include/trace/events/afs.h
index 9a75590227f26272c0fdf23466e063a2f1e4fe64..3dddfc6abf0ee341d3d28a786835e803b2a37663 100644 (file)
--- a/include/trace/events/afs.h
+++ b/include/trace/events/afs.h
@@ -173,6 +173,7 @@ enum yfs_cm_operation {
        EM(afs_cell_trace_get_queue_dns,        "GET q-dns ") \
        EM(afs_cell_trace_get_queue_manage,     "GET q-mng ") \
        EM(afs_cell_trace_get_queue_new,        "GET q-new ") \
+       EM(afs_cell_trace_get_server,           "GET server") \
        EM(afs_cell_trace_get_vol,              "GET vol   ") \
        EM(afs_cell_trace_insert,               "INSERT    ") \
        EM(afs_cell_trace_manage,               "MANAGE    ") \
@@ -180,6 +181,7 @@ enum yfs_cm_operation {
        EM(afs_cell_trace_put_destroy,          "PUT destry") \
        EM(afs_cell_trace_put_queue_work,       "PUT q-work") \
        EM(afs_cell_trace_put_queue_fail,       "PUT q-fail") \
+       EM(afs_cell_trace_put_server,           "PUT server") \
        EM(afs_cell_trace_put_vol,              "PUT vol   ") \
        EM(afs_cell_trace_see_source,           "SEE source") \
        EM(afs_cell_trace_see_ws,               "SEE ws    ") \