[IB] uverbs: Fix device lifetime problems

Move ib_uverbs module to using cdev_alloc() and class_device_create()
so that we can handle device lifetime properly.  Now we can make sure
we keep all of our data structures around until the last way to reach
them is gone.

Signed-off-by: Roland Dreier <rolandd@cisco.com>

3 files changed, 182 insertions, 95 deletions

diff --git a/drivers/infiniband/core/uverbs.h b/drivers/infiniband/core/uverbs.h
index 63c8085c0c98..031cdf3c066d 100644
--- a/drivers/infiniband/core/uverbs.h
+++ b/drivers/infiniband/core/uverbs.h
@@ -39,20 +39,38 @@
 #ifndef UVERBS_H
 #define UVERBS_H
 
-/* Include device.h and fs.h until cdev.h is self-sufficient */
-#include <linux/fs.h>
-#include <linux/device.h>
-#include <linux/cdev.h>
 #include <linux/kref.h>
 #include <linux/idr.h>
 
 #include <rdma/ib_verbs.h>
 #include <rdma/ib_user_verbs.h>
 
+/*
+ * Our lifetime rules for these structs are the following:
+ *
+ * struct ib_uverbs_device: One reference is held by the module and
+ * released in ib_uverbs_remove_one().  Another reference is taken by
+ * ib_uverbs_open() each time the character special file is opened,
+ * and released in ib_uverbs_release_file() when the file is released.
+ *
+ * struct ib_uverbs_file: One reference is held by the VFS and
+ * released when the file is closed.  Another reference is taken when
+ * an asynchronous event queue file is created and released when the
+ * event file is closed.
+ *
+ * struct ib_uverbs_event_file: One reference is held by the VFS and
+ * released when the file is closed.  For asynchronous event files,
+ * another reference is held by the corresponding main context file
+ * and released when that file is closed.  For completion event files,
+ * a reference is taken when a CQ is created that uses the file, and
+ * released when the CQ is destroyed.
+ */
+
 struct ib_uverbs_device {
+        struct kref                             ref;
         int                                     devnum;
-        struct cdev                             dev;
-        struct class_device                     class_dev;
+        struct cdev                            *dev;
+        struct class_device                    *class_dev;
         struct ib_device                       *ib_dev;
         int                                     num_comp_vectors;
 };
@@ -115,6 +133,12 @@ struct file *ib_uverbs_alloc_event_file(struct ib_uverbs_file *uverbs_file,
 void ib_uverbs_release_event_file(struct kref *ref);
 struct ib_uverbs_event_file *ib_uverbs_lookup_comp_file(int fd);
 
+void ib_uverbs_release_ucq(struct ib_uverbs_file *file,
+                           struct ib_uverbs_event_file *ev_file,
+                           struct ib_ucq_object *uobj);
+void ib_uverbs_release_uevent(struct ib_uverbs_file *file,
+                              struct ib_uevent_object *uobj);
+
 void ib_uverbs_comp_handler(struct ib_cq *cq, void *cq_context);
 void ib_uverbs_cq_event_handler(struct ib_event *event, void *context_ptr);
 void ib_uverbs_qp_event_handler(struct ib_event *event, void *context_ptr);
diff --git a/drivers/infiniband/core/uverbs_cmd.c b/drivers/infiniband/core/uverbs_cmd.c
index 14583bb6e2c0..8c89abc8c764 100644
--- a/drivers/infiniband/core/uverbs_cmd.c
+++ b/drivers/infiniband/core/uverbs_cmd.c
@@ -35,6 +35,7 @@
  */
 
 #include <linux/file.h>
+#include <linux/fs.h>
 
 #include <asm/uaccess.h>
 
@@ -114,7 +115,7 @@ ssize_t ib_uverbs_get_context(struct ib_uverbs_file *file,
 
         kref_get(&file->async_file->ref);
         kref_get(&file->ref);
-        file->ucontext   = ucontext;
+        file->ucontext = ucontext;
 
         fd_install(resp.async_fd, filp);
 
@@ -761,7 +762,6 @@ ssize_t ib_uverbs_destroy_cq(struct ib_uverbs_file *file,
         struct ib_cq                    *cq;
         struct ib_ucq_object            *uobj;
         struct ib_uverbs_event_file     *ev_file;
-        struct ib_uverbs_event          *evt, *tmp;
         u64                              user_handle;
         int                              ret = -EINVAL;
 
@@ -790,23 +790,7 @@ ssize_t ib_uverbs_destroy_cq(struct ib_uverbs_file *file,
         list_del(&uobj->uobject.list);
         up(&file->mutex);
 
-        if (ev_file) {
-                spin_lock_irq(&ev_file->lock);
-                list_for_each_entry_safe(evt, tmp, &uobj->comp_list, obj_list) {
-                        list_del(&evt->list);
-                        kfree(evt);
-                }
-                spin_unlock_irq(&ev_file->lock);
-
-                kref_put(&ev_file->ref, ib_uverbs_release_event_file);
-        }
-
-        spin_lock_irq(&file->async_file->lock);
-        list_for_each_entry_safe(evt, tmp, &uobj->async_list, obj_list) {
-                list_del(&evt->list);
-                kfree(evt);
-        }
-        spin_unlock_irq(&file->async_file->lock);
+        ib_uverbs_release_ucq(file, ev_file, uobj);
 
         resp.comp_events_reported  = uobj->comp_events_reported;
         resp.async_events_reported = uobj->async_events_reported;
@@ -1043,7 +1027,6 @@ ssize_t ib_uverbs_destroy_qp(struct ib_uverbs_file *file,
         struct ib_uverbs_destroy_qp_resp resp;
         struct ib_qp                    *qp;
         struct ib_uevent_object         *uobj;
-        struct ib_uverbs_event          *evt, *tmp;
         int                              ret = -EINVAL;
 
         if (copy_from_user(&cmd, buf, sizeof cmd))
@@ -1069,12 +1052,7 @@ ssize_t ib_uverbs_destroy_qp(struct ib_uverbs_file *file,
         list_del(&uobj->uobject.list);
         up(&file->mutex);
 
-        spin_lock_irq(&file->async_file->lock);
-        list_for_each_entry_safe(evt, tmp, &uobj->event_list, obj_list) {
-                list_del(&evt->list);
-                kfree(evt);
-        }
-        spin_unlock_irq(&file->async_file->lock);
+        ib_uverbs_release_uevent(file, uobj);
 
         resp.events_reported = uobj->events_reported;
 
@@ -1741,7 +1719,6 @@ ssize_t ib_uverbs_destroy_srq(struct ib_uverbs_file *file,
         struct ib_uverbs_destroy_srq_resp resp;
         struct ib_srq                    *srq;
         struct ib_uevent_object          *uobj;
-        struct ib_uverbs_event           *evt, *tmp;
         int                               ret = -EINVAL;
 
         if (copy_from_user(&cmd, buf, sizeof cmd))
@@ -1767,12 +1744,7 @@ ssize_t ib_uverbs_destroy_srq(struct ib_uverbs_file *file,
         list_del(&uobj->uobject.list);
         up(&file->mutex);
 
-        spin_lock_irq(&file->async_file->lock);
-        list_for_each_entry_safe(evt, tmp, &uobj->event_list, obj_list) {
-                list_del(&evt->list);
-                kfree(evt);
-        }
-        spin_unlock_irq(&file->async_file->lock);
+        ib_uverbs_release_uevent(file, uobj);
 
         resp.events_reported = uobj->events_reported;
 
diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
index 251c752a7ae6..ac08d2c93ea1 100644
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -44,6 +44,7 @@
 #include <linux/poll.h>
 #include <linux/file.h>
 #include <linux/mount.h>
+#include <linux/cdev.h>
 
 #include <asm/uaccess.h>
 
@@ -63,6 +64,8 @@ enum {
 
 #define IB_UVERBS_BASE_DEV      MKDEV(IB_UVERBS_MAJOR, IB_UVERBS_BASE_MINOR)
 
+static struct class *uverbs_class;
+
 DECLARE_MUTEX(ib_uverbs_idr_mutex);
 DEFINE_IDR(ib_uverbs_pd_idr);
 DEFINE_IDR(ib_uverbs_mr_idr);
@@ -73,6 +76,7 @@ DEFINE_IDR(ib_uverbs_qp_idr);
 DEFINE_IDR(ib_uverbs_srq_idr);
 
 static spinlock_t map_lock;
+static struct ib_uverbs_device *dev_table[IB_UVERBS_MAX_DEVICES];
 static DECLARE_BITMAP(dev_map, IB_UVERBS_MAX_DEVICES);
 
 static ssize_t (*uverbs_cmd_table[])(struct ib_uverbs_file *file,
@@ -110,7 +114,54 @@ static struct vfsmount *uverbs_event_mnt;
 static void ib_uverbs_add_one(struct ib_device *device);
 static void ib_uverbs_remove_one(struct ib_device *device);
 
-static int ib_dealloc_ucontext(struct ib_ucontext *context)
+static void ib_uverbs_release_dev(struct kref *ref)
+{
+        struct ib_uverbs_device *dev =
+                container_of(ref, struct ib_uverbs_device, ref);
+
+        kfree(dev);
+}
+
+void ib_uverbs_release_ucq(struct ib_uverbs_file *file,
+                          struct ib_uverbs_event_file *ev_file,
+                          struct ib_ucq_object *uobj)
+{
+        struct ib_uverbs_event *evt, *tmp;
+
+        if (ev_file) {
+                spin_lock_irq(&ev_file->lock);
+                list_for_each_entry_safe(evt, tmp, &uobj->comp_list, obj_list) {
+                        list_del(&evt->list);
+                        kfree(evt);
+                }
+                spin_unlock_irq(&ev_file->lock);
+
+                kref_put(&ev_file->ref, ib_uverbs_release_event_file);
+        }
+
+        spin_lock_irq(&file->async_file->lock);
+        list_for_each_entry_safe(evt, tmp, &uobj->async_list, obj_list) {
+                list_del(&evt->list);
+                kfree(evt);
+        }
+        spin_unlock_irq(&file->async_file->lock);
+}
+
+void ib_uverbs_release_uevent(struct ib_uverbs_file *file,
+                              struct ib_uevent_object *uobj)
+{
+        struct ib_uverbs_event *evt, *tmp;
+
+        spin_lock_irq(&file->async_file->lock);
+        list_for_each_entry_safe(evt, tmp, &uobj->event_list, obj_list) {
+                list_del(&evt->list);
+                kfree(evt);
+        }
+        spin_unlock_irq(&file->async_file->lock);
+}
+
+static int ib_uverbs_cleanup_ucontext(struct ib_uverbs_file *file,
+                                      struct ib_ucontext *context)
 {
         struct ib_uobject *uobj, *tmp;
 
@@ -129,26 +180,36 @@ static int ib_dealloc_ucontext(struct ib_ucontext *context)
 
         list_for_each_entry_safe(uobj, tmp, &context->qp_list, list) {
                 struct ib_qp *qp = idr_find(&ib_uverbs_qp_idr, uobj->id);
+                struct ib_uevent_object *uevent =
+                        container_of(uobj, struct ib_uevent_object, uobject);
                 idr_remove(&ib_uverbs_qp_idr, uobj->id);
                 ib_destroy_qp(qp);
                 list_del(&uobj->list);
-                kfree(container_of(uobj, struct ib_uevent_object, uobject));
+                ib_uverbs_release_uevent(file, uevent);
+                kfree(uevent);
         }
 
         list_for_each_entry_safe(uobj, tmp, &context->cq_list, list) {
                 struct ib_cq *cq = idr_find(&ib_uverbs_cq_idr, uobj->id);
+                struct ib_uverbs_event_file *ev_file = cq->cq_context;
+                struct ib_ucq_object *ucq =
+                        container_of(uobj, struct ib_ucq_object, uobject);
                 idr_remove(&ib_uverbs_cq_idr, uobj->id);
                 ib_destroy_cq(cq);
                 list_del(&uobj->list);
-                kfree(container_of(uobj, struct ib_ucq_object, uobject));
+                ib_uverbs_release_ucq(file, ev_file, ucq);
+                kfree(ucq);
         }
 
         list_for_each_entry_safe(uobj, tmp, &context->srq_list, list) {
                 struct ib_srq *srq = idr_find(&ib_uverbs_srq_idr, uobj->id);
+                struct ib_uevent_object *uevent =
+                        container_of(uobj, struct ib_uevent_object, uobject);
                 idr_remove(&ib_uverbs_srq_idr, uobj->id);
                 ib_destroy_srq(srq);
                 list_del(&uobj->list);
-                kfree(container_of(uobj, struct ib_uevent_object, uobject));
+                ib_uverbs_release_uevent(file, uevent);
+                kfree(uevent);
         }
 
         /* XXX Free MWs */
@@ -187,6 +248,8 @@ static void ib_uverbs_release_file(struct kref *ref)
                 container_of(ref, struct ib_uverbs_file, ref);
 
         module_put(file->device->ib_dev->owner);
+        kref_put(&file->device->ref, ib_uverbs_release_dev);
+
         kfree(file);
 }
 
@@ -552,36 +615,58 @@ static int ib_uverbs_mmap(struct file *filp, struct vm_area_struct *vma)
 
 static int ib_uverbs_open(struct inode *inode, struct file *filp)
 {
-        struct ib_uverbs_device *dev =
-                container_of(inode->i_cdev, struct ib_uverbs_device, dev);
+        struct ib_uverbs_device *dev;
         struct ib_uverbs_file *file;
+        int ret;
 
-        if (!try_module_get(dev->ib_dev->owner))
-                return -ENODEV;
+        spin_lock(&map_lock);
+        dev = dev_table[iminor(inode) - IB_UVERBS_BASE_MINOR];
+        if (dev)
+                kref_get(&dev->ref);
+        spin_unlock(&map_lock);
+
+        if (!dev)
+                return -ENXIO;
+
+        if (!try_module_get(dev->ib_dev->owner)) {
+                ret = -ENODEV;
+                goto err;
+        }
 
         file = kmalloc(sizeof *file, GFP_KERNEL);
         if (!file) {
-                module_put(dev->ib_dev->owner);
-                return -ENOMEM;
+                ret = -ENOMEM;
+                goto err_module;
         }
 
-        file->device   = dev;
-        file->ucontext = NULL;
+        file->device     = dev;
+        file->ucontext   = NULL;
+        file->async_file = NULL;
         kref_init(&file->ref);
         init_MUTEX(&file->mutex);
 
         filp->private_data = file;
 
         return 0;
+
+err_module:
+        module_put(dev->ib_dev->owner);
+
+err:
+        kref_put(&dev->ref, ib_uverbs_release_dev);
+
+        return ret;
 }
 
 static int ib_uverbs_close(struct inode *inode, struct file *filp)
 {
         struct ib_uverbs_file *file = filp->private_data;
 
-        ib_dealloc_ucontext(file->ucontext);
+        ib_uverbs_cleanup_ucontext(file, file->ucontext);
+
+        if (file->async_file)
+                kref_put(&file->async_file->ref, ib_uverbs_release_event_file);
 
-        kref_put(&file->async_file->ref, ib_uverbs_release_event_file);
         kref_put(&file->ref, ib_uverbs_release_file);
 
         return 0;
@@ -610,8 +695,10 @@ static struct ib_client uverbs_client = {
 
 static ssize_t show_ibdev(struct class_device *class_dev, char *buf)
 {
-        struct ib_uverbs_device *dev =
-                container_of(class_dev, struct ib_uverbs_device, class_dev);
+        struct ib_uverbs_device *dev = class_get_devdata(class_dev);
+
+        if (!dev)
+                return -ENODEV;
 
         return sprintf(buf, "%s\n", dev->ib_dev->name);
 }
@@ -619,28 +706,15 @@ static CLASS_DEVICE_ATTR(ibdev, S_IRUGO, show_ibdev, NULL);
 
 static ssize_t show_dev_abi_version(struct class_device *class_dev, char *buf)
 {
-        struct ib_uverbs_device *dev =
-                container_of(class_dev, struct ib_uverbs_device, class_dev);
+        struct ib_uverbs_device *dev = class_get_devdata(class_dev);
+
+        if (!dev)
+                return -ENODEV;
 
         return sprintf(buf, "%d\n", dev->ib_dev->uverbs_abi_ver);
 }
 static CLASS_DEVICE_ATTR(abi_version, S_IRUGO, show_dev_abi_version, NULL);
 
-static void ib_uverbs_release_class_dev(struct class_device *class_dev)
-{
-        struct ib_uverbs_device *dev =
-                container_of(class_dev, struct ib_uverbs_device, class_dev);
-
-        cdev_del(&dev->dev);
-        clear_bit(dev->devnum, dev_map);
-        kfree(dev);
-}
-
-static struct class uverbs_class = {
-        .name    = "infiniband_verbs",
-        .release = ib_uverbs_release_class_dev
-};
-
 static ssize_t show_abi_version(struct class *class, char *buf)
 {
         return sprintf(buf, "%d\n", IB_USER_VERBS_ABI_VERSION);
@@ -660,6 +734,8 @@ static void ib_uverbs_add_one(struct ib_device *device)
 
         memset(uverbs_dev, 0, sizeof *uverbs_dev);
 
+        kref_init(&uverbs_dev->ref);
+
         spin_lock(&map_lock);
         uverbs_dev->devnum = find_first_zero_bit(dev_map, IB_UVERBS_MAX_DEVICES);
         if (uverbs_dev->devnum >= IB_UVERBS_MAX_DEVICES) {
@@ -672,40 +748,45 @@ static void ib_uverbs_add_one(struct ib_device *device)
         uverbs_dev->ib_dev           = device;
         uverbs_dev->num_comp_vectors = 1;
 
-        if (device->mmap)
-                cdev_init(&uverbs_dev->dev, &uverbs_mmap_fops);
-        else
-                cdev_init(&uverbs_dev->dev, &uverbs_fops);
-        uverbs_dev->dev.owner = THIS_MODULE;
-        kobject_set_name(&uverbs_dev->dev.kobj, "uverbs%d", uverbs_dev->devnum);
-        if (cdev_add(&uverbs_dev->dev, IB_UVERBS_BASE_DEV + uverbs_dev->devnum, 1))
+        uverbs_dev->dev = cdev_alloc();
+        if (!uverbs_dev->dev)
                 goto err;
+        uverbs_dev->dev->owner = THIS_MODULE;
+        uverbs_dev->dev->ops = device->mmap ? &uverbs_mmap_fops : &uverbs_fops;
+        kobject_set_name(&uverbs_dev->dev->kobj, "uverbs%d", uverbs_dev->devnum);
+        if (cdev_add(uverbs_dev->dev, IB_UVERBS_BASE_DEV + uverbs_dev->devnum, 1))
+                goto err_cdev;
 
-        uverbs_dev->class_dev.class = &uverbs_class;
-        uverbs_dev->class_dev.dev   = device->dma_device;
-        uverbs_dev->class_dev.devt  = uverbs_dev->dev.dev;
-        snprintf(uverbs_dev->class_dev.class_id, BUS_ID_SIZE, "uverbs%d", uverbs_dev->devnum);
-        if (class_device_register(&uverbs_dev->class_dev))
+        uverbs_dev->class_dev = class_device_create(uverbs_class, uverbs_dev->dev->dev,
+                                                    device->dma_device,
+                                                    "uverbs%d", uverbs_dev->devnum);
+        if (IS_ERR(uverbs_dev->class_dev))
                 goto err_cdev;
 
-        if (class_device_create_file(&uverbs_dev->class_dev, &class_device_attr_ibdev))
+        class_set_devdata(uverbs_dev->class_dev, uverbs_dev);
+
+        if (class_device_create_file(uverbs_dev->class_dev, &class_device_attr_ibdev))
                 goto err_class;
-        if (class_device_create_file(&uverbs_dev->class_dev, &class_device_attr_abi_version))
+        if (class_device_create_file(uverbs_dev->class_dev, &class_device_attr_abi_version))
                 goto err_class;
 
+        spin_lock(&map_lock);
+        dev_table[uverbs_dev->devnum] = uverbs_dev;
+        spin_unlock(&map_lock);
+
         ib_set_client_data(device, &uverbs_client, uverbs_dev);
 
         return;
 
 err_class:
-        class_device_unregister(&uverbs_dev->class_dev);
+        class_device_destroy(uverbs_class, uverbs_dev->dev->dev);
 
 err_cdev:
-        cdev_del(&uverbs_dev->dev);
+        cdev_del(uverbs_dev->dev);
         clear_bit(uverbs_dev->devnum, dev_map);
 
 err:
-        kfree(uverbs_dev);
+        kref_put(&uverbs_dev->ref, ib_uverbs_release_dev);
         return;
 }
 
@@ -716,7 +797,16 @@ static void ib_uverbs_remove_one(struct ib_device *device)
         if (!uverbs_dev)
                 return;
 
-        class_device_unregister(&uverbs_dev->class_dev);
+        class_set_devdata(uverbs_dev->class_dev, NULL);
+        class_device_destroy(uverbs_class, uverbs_dev->dev->dev);
+        cdev_del(uverbs_dev->dev);
+
+        spin_lock(&map_lock);
+        dev_table[uverbs_dev->devnum] = NULL;
+        spin_unlock(&map_lock);
+
+        clear_bit(uverbs_dev->devnum, dev_map);
+        kref_put(&uverbs_dev->ref, ib_uverbs_release_dev);
 }
 
 static struct super_block *uverbs_event_get_sb(struct file_system_type *fs_type, int flags,
@@ -746,13 +836,14 @@ static int __init ib_uverbs_init(void)
                 goto out;
         }
 
-        ret = class_register(&uverbs_class);
-        if (ret) {
+        uverbs_class = class_create(THIS_MODULE, "infiniband_verbs");
+        if (IS_ERR(uverbs_class)) {
+                ret = PTR_ERR(uverbs_class);
                 printk(KERN_ERR "user_verbs: couldn't create class infiniband_verbs\n");
                 goto out_chrdev;
         }
 
-        ret = class_create_file(&uverbs_class, &class_attr_abi_version);
+        ret = class_create_file(uverbs_class, &class_attr_abi_version);
         if (ret) {
                 printk(KERN_ERR "user_verbs: couldn't create abi_version attribute\n");
                 goto out_class;
@@ -786,7 +877,7 @@ out_fs:
         unregister_filesystem(&uverbs_event_fs);
 
 out_class:
-        class_unregister(&uverbs_class);
+        class_destroy(uverbs_class);
 
 out_chrdev:
         unregister_chrdev_region(IB_UVERBS_BASE_DEV, IB_UVERBS_MAX_DEVICES);
@@ -800,7 +891,7 @@ static void __exit ib_uverbs_cleanup(void)
         ib_unregister_client(&uverbs_client);
         mntput(uverbs_event_mnt);
         unregister_filesystem(&uverbs_event_fs);
-        class_unregister(&uverbs_class);
+        class_destroy(uverbs_class);
         unregister_chrdev_region(IB_UVERBS_BASE_DEV, IB_UVERBS_MAX_DEVICES);
         idr_destroy(&ib_uverbs_pd_idr);
         idr_destroy(&ib_uverbs_mr_idr);