From: Guoqing Jiang guoqing.jiang@cloud.ionos.com
[ Upstream commit d715ff8acbd5876549ef2b21b755ed919f40dcc1 ]
The purpose of srv_mutex is to protect srv_list as in put_srv, so no need to hold it when allocate memory for srv since it could be time consuming.
Otherwise if one machine has limited memory, rsrv_close_work could be blocked for a longer time due to the mutex is held by get_or_create_srv since it can't get memory in time.
INFO: task kworker/1:1:27478 blocked for more than 120 seconds. Tainted: G O 4.14.171-1-storage #4.14.171-1.3~deb9 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/1:1 D 0 27478 2 0x80000000 Workqueue: rtrs_server_wq rtrs_srv_close_work [rtrs_server] Call Trace: ? __schedule+0x38c/0x7e0 schedule+0x32/0x80 schedule_preempt_disabled+0xa/0x10 __mutex_lock.isra.2+0x25e/0x4d0 ? put_srv+0x44/0x100 [rtrs_server] put_srv+0x44/0x100 [rtrs_server] rtrs_srv_close_work+0x16c/0x280 [rtrs_server] process_one_work+0x1c5/0x3c0 worker_thread+0x47/0x3e0 kthread+0xfc/0x130 ? trace_event_raw_event_workqueue_execute_start+0xa0/0xa0 ? kthread_create_on_node+0x70/0x70 ret_from_fork+0x1f/0x30
Let's move all the logics from __find_srv_and_get and __alloc_srv to get_or_create_srv, and remove the two functions. Then it should be safe for multiple processes to access the same srv since it is protected with srv_mutex.
And since we don't want to allocate chunks with srv_mutex held, let's check the srv->refcount after get srv because the chunks could not be allocated yet.
Fixes: 9cb837480424 ("RDMA/rtrs: server: main functionality") Link: https://lore.kernel.org/r/20201023074353.21946-6-jinpu.wang@cloud.ionos.com Signed-off-by: Guoqing Jiang guoqing.jiang@cloud.ionos.com Signed-off-by: Jack Wang jinpu.wang@cloud.ionos.com Signed-off-by: Jason Gunthorpe jgg@nvidia.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/infiniband/ulp/rtrs/rtrs-srv.c | 86 +++++++++++--------------- 1 file changed, 37 insertions(+), 49 deletions(-)
diff --git a/drivers/infiniband/ulp/rtrs/rtrs-srv.c b/drivers/infiniband/ulp/rtrs/rtrs-srv.c index d6f93601712e4..1cb778aff3c59 100644 --- a/drivers/infiniband/ulp/rtrs/rtrs-srv.c +++ b/drivers/infiniband/ulp/rtrs/rtrs-srv.c @@ -1328,17 +1328,42 @@ static void rtrs_srv_dev_release(struct device *dev) kfree(srv); }
-static struct rtrs_srv *__alloc_srv(struct rtrs_srv_ctx *ctx, - const uuid_t *paths_uuid) +static void free_srv(struct rtrs_srv *srv) +{ + int i; + + WARN_ON(refcount_read(&srv->refcount)); + for (i = 0; i < srv->queue_depth; i++) + mempool_free(srv->chunks[i], chunk_pool); + kfree(srv->chunks); + mutex_destroy(&srv->paths_mutex); + mutex_destroy(&srv->paths_ev_mutex); + /* last put to release the srv structure */ + put_device(&srv->dev); +} + +static struct rtrs_srv *get_or_create_srv(struct rtrs_srv_ctx *ctx, + const uuid_t *paths_uuid) { struct rtrs_srv *srv; int i;
+ mutex_lock(&ctx->srv_mutex); + list_for_each_entry(srv, &ctx->srv_list, ctx_list) { + if (uuid_equal(&srv->paths_uuid, paths_uuid) && + refcount_inc_not_zero(&srv->refcount)) { + mutex_unlock(&ctx->srv_mutex); + return srv; + } + } + + /* need to allocate a new srv */ srv = kzalloc(sizeof(*srv), GFP_KERNEL); - if (!srv) + if (!srv) { + mutex_unlock(&ctx->srv_mutex); return NULL; + }
- refcount_set(&srv->refcount, 1); INIT_LIST_HEAD(&srv->paths_list); mutex_init(&srv->paths_mutex); mutex_init(&srv->paths_ev_mutex); @@ -1347,6 +1372,8 @@ static struct rtrs_srv *__alloc_srv(struct rtrs_srv_ctx *ctx, srv->ctx = ctx; device_initialize(&srv->dev); srv->dev.release = rtrs_srv_dev_release; + list_add(&srv->ctx_list, &ctx->srv_list); + mutex_unlock(&ctx->srv_mutex);
srv->chunks = kcalloc(srv->queue_depth, sizeof(*srv->chunks), GFP_KERNEL); @@ -1358,7 +1385,7 @@ static struct rtrs_srv *__alloc_srv(struct rtrs_srv_ctx *ctx, if (!srv->chunks[i]) goto err_free_chunks; } - list_add(&srv->ctx_list, &ctx->srv_list); + refcount_set(&srv->refcount, 1);
return srv;
@@ -1369,52 +1396,9 @@ err_free_chunks:
err_free_srv: kfree(srv); - return NULL; }
-static void free_srv(struct rtrs_srv *srv) -{ - int i; - - WARN_ON(refcount_read(&srv->refcount)); - for (i = 0; i < srv->queue_depth; i++) - mempool_free(srv->chunks[i], chunk_pool); - kfree(srv->chunks); - mutex_destroy(&srv->paths_mutex); - mutex_destroy(&srv->paths_ev_mutex); - /* last put to release the srv structure */ - put_device(&srv->dev); -} - -static inline struct rtrs_srv *__find_srv_and_get(struct rtrs_srv_ctx *ctx, - const uuid_t *paths_uuid) -{ - struct rtrs_srv *srv; - - list_for_each_entry(srv, &ctx->srv_list, ctx_list) { - if (uuid_equal(&srv->paths_uuid, paths_uuid) && - refcount_inc_not_zero(&srv->refcount)) - return srv; - } - - return NULL; -} - -static struct rtrs_srv *get_or_create_srv(struct rtrs_srv_ctx *ctx, - const uuid_t *paths_uuid) -{ - struct rtrs_srv *srv; - - mutex_lock(&ctx->srv_mutex); - srv = __find_srv_and_get(ctx, paths_uuid); - if (!srv) - srv = __alloc_srv(ctx, paths_uuid); - mutex_unlock(&ctx->srv_mutex); - - return srv; -} - static void put_srv(struct rtrs_srv *srv) { if (refcount_dec_and_test(&srv->refcount)) { @@ -1813,7 +1797,11 @@ static int rtrs_rdma_connect(struct rdma_cm_id *cm_id, } recon_cnt = le16_to_cpu(msg->recon_cnt); srv = get_or_create_srv(ctx, &msg->paths_uuid); - if (!srv) { + /* + * "refcount == 0" happens if a previous thread calls get_or_create_srv + * allocate srv, but chunks of srv are not allocated yet. + */ + if (!srv || refcount_read(&srv->refcount) == 0) { err = -ENOMEM; goto reject_w_err; }