From 6898d1c661d79f4707d8ba82991b2195822780ca Mon Sep 17 00:00:00 2001 From: Jason Gunthorpe Date: Wed, 8 Jan 2020 19:21:53 +0200 Subject: [PATCH] RDMA/mlx5: Use RCU and direct refcounts to keep memory alive dispatch_event_fd() runs from a notifier with minimal locking, and relies on RCU and a file refcount to keep the uobject and eventfd alive. As the next patch wants to remove the file_operations release function from the drivers, re-organize things so that the devx_event_notifier() path uses the existing RCU to manage the lifetime of the uobject and eventfd. Move the refcount puts to a call_rcu so that the objects are guaranteed to exist and remove the indirect file refcount. Link: https://lore.kernel.org/r/1578504126-9400-2-git-send-email-yishaih@mellanox.com Signed-off-by: Yishai Hadas Signed-off-by: Jason Gunthorpe --- drivers/infiniband/core/rdma_core.c | 11 +++++----- drivers/infiniband/core/rdma_core.h | 15 ------------- drivers/infiniband/hw/mlx5/devx.c | 34 ++++++++++++++--------------- include/rdma/uverbs_types.h | 12 ++++++++++ 4 files changed, 35 insertions(+), 37 deletions(-) diff --git a/drivers/infiniband/core/rdma_core.c b/drivers/infiniband/core/rdma_core.c index 17bdbe38fdfa..aef6fb823206 100644 --- a/drivers/infiniband/core/rdma_core.c +++ b/drivers/infiniband/core/rdma_core.c @@ -42,20 +42,21 @@ #include "core_priv.h" #include "rdma_core.h" -void uverbs_uobject_get(struct ib_uobject *uobject) -{ - kref_get(&uobject->ref); -} - static void uverbs_uobject_free(struct kref *ref) { kfree_rcu(container_of(ref, struct ib_uobject, ref), rcu); } +/* + * In order to indicate we no longer needs this uobject, uverbs_uobject_put + * is called. When the reference count is decreased, the uobject is freed. + * For example, this is used when attaching a completion channel to a CQ. + */ void uverbs_uobject_put(struct ib_uobject *uobject) { kref_put(&uobject->ref, uverbs_uobject_free); } +EXPORT_SYMBOL(uverbs_uobject_put); static int uverbs_try_lock_object(struct ib_uobject *uobj, enum rdma_lookup_mode mode) diff --git a/drivers/infiniband/core/rdma_core.h b/drivers/infiniband/core/rdma_core.h index e63fbda25e1d..d5d58a10bb28 100644 --- a/drivers/infiniband/core/rdma_core.h +++ b/drivers/infiniband/core/rdma_core.h @@ -50,21 +50,6 @@ void uverbs_destroy_ufile_hw(struct ib_uverbs_file *ufile, int uobj_destroy(struct ib_uobject *uobj, struct uverbs_attr_bundle *attrs); -/* - * uverbs_uobject_get is called in order to increase the reference count on - * an uobject. This is useful when a handler wants to keep the uobject's memory - * alive, regardless if this uobject is still alive in the context's objects - * repository. Objects are put via uverbs_uobject_put. - */ -void uverbs_uobject_get(struct ib_uobject *uobject); - -/* - * In order to indicate we no longer needs this uobject, uverbs_uobject_put - * is called. When the reference count is decreased, the uobject is freed. - * For example, this is used when attaching a completion channel to a CQ. - */ -void uverbs_uobject_put(struct ib_uobject *uobject); - /* Indicate this fd is no longer used by this consumer, but its memory isn't * necessarily released yet. When the last reference is put, we release the * memory. After this call is executed, calling uverbs_uobject_get isn't diff --git a/drivers/infiniband/hw/mlx5/devx.c b/drivers/infiniband/hw/mlx5/devx.c index 9d0a18cf9e5e..968fff018fc0 100644 --- a/drivers/infiniband/hw/mlx5/devx.c +++ b/drivers/infiniband/hw/mlx5/devx.c @@ -72,7 +72,6 @@ struct devx_event_subscription { struct rcu_head rcu; u64 cookie; struct devx_async_event_file *ev_file; - struct file *filp; /* Upon hot unplug we need a direct access to */ struct eventfd_ctx *eventfd; }; @@ -2032,6 +2031,7 @@ static int UVERBS_HANDLER(MLX5_IB_METHOD_DEVX_SUBSCRIBE_EVENT)( goto err; list_add_tail(&event_sub->event_list, &sub_list); + uverbs_uobject_get(&ev_file->uobj); if (use_eventfd) { event_sub->eventfd = eventfd_ctx_fdget(redirect_fd); @@ -2045,7 +2045,6 @@ static int UVERBS_HANDLER(MLX5_IB_METHOD_DEVX_SUBSCRIBE_EVENT)( event_sub->cookie = cookie; event_sub->ev_file = ev_file; - event_sub->filp = fd_uobj->object; /* May be needed upon cleanup the devx object/subscription */ event_sub->xa_key_level1 = key_level1; event_sub->xa_key_level2 = obj_id; @@ -2099,7 +2098,7 @@ static int UVERBS_HANDLER(MLX5_IB_METHOD_DEVX_SUBSCRIBE_EVENT)( if (event_sub->eventfd) eventfd_ctx_put(event_sub->eventfd); - + uverbs_uobject_put(&event_sub->ev_file->uobj); kfree(event_sub); } @@ -2361,17 +2360,10 @@ static void dispatch_event_fd(struct list_head *fd_list, struct devx_event_subscription *item; list_for_each_entry_rcu(item, fd_list, xa_list) { - if (!get_file_rcu(item->filp)) - continue; - - if (item->eventfd) { + if (item->eventfd) eventfd_signal(item->eventfd, 1); - fput(item->filp); - continue; - } - - deliver_event(item, data); - fput(item->filp); + else + deliver_event(item, data); } } @@ -2653,6 +2645,17 @@ static __poll_t devx_async_event_poll(struct file *filp, return pollflags; } +static void devx_free_subscription(struct rcu_head *rcu) +{ + struct devx_event_subscription *event_sub = + container_of(rcu, struct devx_event_subscription, rcu); + + if (event_sub->eventfd) + eventfd_ctx_put(event_sub->eventfd); + uverbs_uobject_put(&event_sub->ev_file->uobj); + kfree(event_sub); +} + static int devx_async_event_close(struct inode *inode, struct file *filp) { struct devx_async_event_file *ev_file = filp->private_data; @@ -2665,12 +2668,9 @@ static int devx_async_event_close(struct inode *inode, struct file *filp) list_for_each_entry_safe(event_sub, event_sub_tmp, &ev_file->subscribed_events_list, file_list) { devx_cleanup_subscription(dev, event_sub); - if (event_sub->eventfd) - eventfd_ctx_put(event_sub->eventfd); - list_del_rcu(&event_sub->file_list); /* subscription may not be used by the read API any more */ - kfree_rcu(event_sub, rcu); + call_rcu(&event_sub->rcu, devx_free_subscription); } mutex_unlock(&dev->devx_event_table.event_xa_lock); diff --git a/include/rdma/uverbs_types.h b/include/rdma/uverbs_types.h index 0b0f5a5f392d..ca65d4704b4b 100644 --- a/include/rdma/uverbs_types.h +++ b/include/rdma/uverbs_types.h @@ -144,6 +144,18 @@ void rdma_alloc_abort_uobject(struct ib_uobject *uobj, int __must_check rdma_alloc_commit_uobject(struct ib_uobject *uobj, struct uverbs_attr_bundle *attrs); +/* + * uverbs_uobject_get is called in order to increase the reference count on + * an uobject. This is useful when a handler wants to keep the uobject's memory + * alive, regardless if this uobject is still alive in the context's objects + * repository. Objects are put via uverbs_uobject_put. + */ +static inline void uverbs_uobject_get(struct ib_uobject *uobject) +{ + kref_get(&uobject->ref); +} +void uverbs_uobject_put(struct ib_uobject *uobject); + struct uverbs_obj_fd_type { /* * In fd based objects, uverbs_obj_type_ops points to generic -- 2.45.2