[PATCH v13 01/59] libceph: add spinlock around osd->o_requests

Jeff Layton
2022-04-06T00:35:12Z

In a later patch, we're going to need to search for a request in
the rbtree, but taking the o_mutex is inconvenient as we already
hold the con mutex at the point where we need it.

Add a new spinlock that we take when inserting and erasing entries from
the o_requests tree. Search of the rbtree can be done with either the
mutex or the spinlock, but insertion and removal requires both.

Reviewed-by: Xiubo Li <xiubli@redhat.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
include/linux/ceph/osd_client.h | 8 +++++++-
net/ceph/osd_client.c | 5 +++++
2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/include/linux/ceph/osd_client.h b/include/linux/ceph/osd_client.h
index 3431011f364d..3122c1a3205f 100644
--- a/include/linux/ceph/osd_client.h
+++ b/include/linux/ceph/osd_client.h
@@ -29,7 +29,12 @@ typedef void (*ceph_osdc_callback_t)(struct ceph_osd_request *);

#define CEPH_HOMELESS_OSD -1

-/* a given osd we're communicating with */
+/*
+ * A given osd we're communicating with.
+ *
+ * Note that the o_requests tree can be searched while holding the "lock" mutex
+ * or the "o_requests_lock" spinlock. Insertion or removal requires both!
+ */
struct ceph_osd {
refcount_t o_ref;
struct ceph_osd_client *o_osdc;
@@ -37,6 +42,7 @@ struct ceph_osd {
int o_incarnation;
struct rb_node o_node;
struct ceph_connection o_con;
+ spinlock_t o_requests_lock;
struct rb_root o_requests;
struct rb_root o_linger_requests;
struct rb_root o_backoff_mappings;
diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index 83eb97c94e83..17c792b32343 100644
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c
@@ -1198,6 +1198,7 @@ static void osd_init(struct ceph_osd *osd)
{
refcount_set(&osd->o_ref, 1);
RB_CLEAR_NODE(&osd->o_node);
+ spin_lock_init(&osd->o_requests_lock);
osd->o_requests = RB_ROOT;
osd->o_linger_requests = RB_ROOT;
osd->o_backoff_mappings = RB_ROOT;
@@ -1427,7 +1428,9 @@ static void link_request(struct ceph_osd *osd, struct ceph_osd_request *req)
atomic_inc(&osd->o_osdc->num_homeless);

get_osd(osd);
+ spin_lock(&osd->o_requests_lock);
insert_request(&osd->o_requests, req);
+ spin_unlock(&osd->o_requests_lock);
req->r_osd = osd;
}

@@ -1439,7 +1442,9 @@ static void unlink_request(struct ceph_osd *osd, struct ceph_osd_request *req)
req, req->r_tid);

req->r_osd = NULL;
+ spin_lock(&osd->o_requests_lock);
erase_request(&osd->o_requests, req);
+ spin_unlock(&osd->o_requests_lock);
put_osd(osd);

if (!osd_homeless(osd))
--
2.35.1