[PATCH for-next V7 0/6] HW Device hot-removal support

[PATCH for-next V7 0/6] HW Device hot-removal support

[Yishai Hadas]

Currently, if there is any user space application using an IB device,
it is impossible to unload the HW device driver for this device.

Similarly, if the device is hot-unplugged or reset, the device driver
hardware removal flow blocks until all user contexts are destroyed.

This patchset removes the above limitations from both uverbs and ucma.

The IB-core and uverbs layers are still required to remain loaded as
long as there are user applications using the verbs API. However, the
hardware device drivers are not blocked any more by the user space
activity.

To support this, the hardware device needs to expose a new kernel API
named 'disassociate_ucontext'. The device driver is given a ucontext
to detach from, and it should block this user context from any future
hardware access. In the IB-core level, we use this interface to
deactivate all ucontext that address a specific device when handling a
remove_one callback for it.

In the RDMA-CM layer, a similar change is needed in the ucma module,
to prevent blocking of the remove_one operation. This allows for
hot-removal of devices with RDMA-CM users in the user space.

The first three patches are preparation for this series.
The first patch fixes a reference counting issue pointed by Jason Gunthorpe.
The second patch fixes a race condition issue pointed by Jason Gunthorpe.
The third patch is a preparation step for deploying RCU for the device
removal flow.

The fourth patch introduces the new API between the HW device driver and
the IB core. For devices which implement the functionality, IB core
will use it in remove_one, disassociating any active ucontext from the
hardware device. Other drivers that didn't implement it will behave as
today, remove_one will block until all ucontexts referring the device
are destroyed before returning.

The fifth patch provides implementation of this API for the mlx4
driver.

The last patch extends ucma to avoid blocking remove_one operation in
the cma module. When such device removal event is received, ucma is
turning all user contexts to zombie contexts. This is done by
releasing all underlying resources and preventing any further user
operations on the context.

Changes from V6:
Added an extra patch #2 to solve a race that was introduced 5 years ago and was reported by Jason.
patch #4 (previously #3): Adapted to the fix of patch #2.

Changes from V5:
Addressed Jason's comments for below patches:
patch #1: Improve kref usage.
patch #3: Use 2 different krefs for complete and memory, improve some comments.

Changes from V4:
patch #1,#3 - addressed Jason's comments.
patch #2, #4 - rebased upon last stuff.

Changes from V3:
Add 2 patches as a preparation for this series, details above.
patch #3: Change the locking schema based on Jason's comments.

Changes from V2:
patch #1: Rebase over ODP patches.

Changes from V1:
patch #1: Use uverbs flags instead of disassociate support, drop fatal_event_raised flag.
patch #3: Add support in ucma for handling device removal.

Changes from V0:
patch #1: ib_uverbs_close, reduced mutex scope to enable tasks run in parallel.
Yishai Hadas (6):
  IB/uverbs: Fix reference counting usage of event files
  IB/uverbs: Fix race between ib_uverbs_open and remove_one
  IB/uverbs: Explicitly pass ib_dev to uverbs commands
  IB/uverbs: Enable device removal when there are active user space
    applications
  IB/mlx4_ib: Disassociate support
  IB/ucma: HW Device hot-removal support

 drivers/infiniband/core/ucma.c        |  130 +++++++++-
 drivers/infiniband/core/uverbs.h      |   16 +-
 drivers/infiniband/core/uverbs_cmd.c  |  114 ++++++----
 drivers/infiniband/core/uverbs_main.c |  442 +++++++++++++++++++++++++++------
 drivers/infiniband/hw/mlx4/main.c     |  139 ++++++++++-
 drivers/infiniband/hw/mlx4/mlx4_ib.h  |   13 +
 include/rdma/ib_verbs.h               |    1 +
 7 files changed, 718 insertions(+), 137 deletions(-)

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[PATCH for-next V7 1/6] IB/uverbs: Fix reference counting usage of event files

[Yishai Hadas]

Fix the reference counting usage to be handled in the event file
creation/destruction function, instead of being done by the caller.
This is done for both async/non-async event files.

Based on Jason Gunthorpe report at https://www.mail-archive.com/
linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org/msg24680.html:
"The existing code for this is broken, in ib_uverbs_get_context all
the error paths between ib_uverbs_alloc_event_file and the
kref_get(file->ref) are wrong - this will result in fput() which will
call ib_uverbs_event_close, which will try to do kref_put and
ib_unregister_event_handler - which are no longer paired."

Signed-off-by: Yishai Hadas <yishaih-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Signed-off-by: Shachar Raindel <raindel-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
---
 drivers/infiniband/core/uverbs.h      |    1 +
 drivers/infiniband/core/uverbs_cmd.c  |   11 +-------
 drivers/infiniband/core/uverbs_main.c |   44 ++++++++++++++++++++++++++++----
 3 files changed, 40 insertions(+), 16 deletions(-)

diff --git a/drivers/infiniband/core/uverbs.h b/drivers/infiniband/core/uverbs.h
index ba365b6..60e6e3d 100644
--- a/drivers/infiniband/core/uverbs.h
+++ b/drivers/infiniband/core/uverbs.h
@@ -178,6 +178,7 @@ void idr_remove_uobj(struct idr *idp, struct ib_uobject *uobj);
 
 struct file *ib_uverbs_alloc_event_file(struct ib_uverbs_file *uverbs_file,
 					int is_async);
+void ib_uverbs_free_async_event_file(struct ib_uverbs_file *uverbs_file);
 struct ib_uverbs_event_file *ib_uverbs_lookup_comp_file(int fd);
 
 void ib_uverbs_release_ucq(struct ib_uverbs_file *file,
diff --git a/drivers/infiniband/core/uverbs_cmd.c b/drivers/infiniband/core/uverbs_cmd.c
index bbb02ff..5720a92 100644
--- a/drivers/infiniband/core/uverbs_cmd.c
+++ b/drivers/infiniband/core/uverbs_cmd.c
@@ -367,16 +367,6 @@ ssize_t ib_uverbs_get_context(struct ib_uverbs_file *file,
 		goto err_file;
 	}
 
-	file->async_file = filp->private_data;
-
-	INIT_IB_EVENT_HANDLER(&file->event_handler, file->device->ib_dev,
-			      ib_uverbs_event_handler);
-	ret = ib_register_event_handler(&file->event_handler);
-	if (ret)
-		goto err_file;
-
-	kref_get(&file->async_file->ref);
-	kref_get(&file->ref);
 	file->ucontext = ucontext;
 
 	fd_install(resp.async_fd, filp);
@@ -386,6 +376,7 @@ ssize_t ib_uverbs_get_context(struct ib_uverbs_file *file,
 	return in_len;
 
 err_file:
+	ib_uverbs_free_async_event_file(file);
 	fput(filp);
 
 err_fd:
diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
index f6eef2d..c238eba 100644
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -406,10 +406,9 @@ static int ib_uverbs_event_close(struct inode *inode, struct file *filp)
 	}
 	spin_unlock_irq(&file->lock);
 
-	if (file->is_async) {
+	if (file->is_async)
 		ib_unregister_event_handler(&file->uverbs_file->event_handler);
-		kref_put(&file->uverbs_file->ref, ib_uverbs_release_file);
-	}
+	kref_put(&file->uverbs_file->ref, ib_uverbs_release_file);
 	kref_put(&file->ref, ib_uverbs_release_event_file);
 
 	return 0;
@@ -541,13 +540,20 @@ void ib_uverbs_event_handler(struct ib_event_handler *handler,
 				NULL, NULL);
 }
 
+void ib_uverbs_free_async_event_file(struct ib_uverbs_file *file)
+{
+	kref_put(&file->async_file->ref, ib_uverbs_release_event_file);
+	file->async_file = NULL;
+}
+
 struct file *ib_uverbs_alloc_event_file(struct ib_uverbs_file *uverbs_file,
 					int is_async)
 {
 	struct ib_uverbs_event_file *ev_file;
 	struct file *filp;
+	int ret;
 
-	ev_file = kmalloc(sizeof *ev_file, GFP_KERNEL);
+	ev_file = kzalloc(sizeof(*ev_file), GFP_KERNEL);
 	if (!ev_file)
 		return ERR_PTR(-ENOMEM);
 
@@ -556,15 +562,41 @@ struct file *ib_uverbs_alloc_event_file(struct ib_uverbs_file *uverbs_file,
 	INIT_LIST_HEAD(&ev_file->event_list);
 	init_waitqueue_head(&ev_file->poll_wait);
 	ev_file->uverbs_file = uverbs_file;
+	kref_get(&ev_file->uverbs_file->ref);
 	ev_file->async_queue = NULL;
-	ev_file->is_async    = is_async;
 	ev_file->is_closed   = 0;
 
 	filp = anon_inode_getfile("[infinibandevent]", &uverbs_event_fops,
 				  ev_file, O_RDONLY);
 	if (IS_ERR(filp))
-		kfree(ev_file);
+		goto err_put_refs;
+
+	if (is_async) {
+		WARN_ON(uverbs_file->async_file);
+		uverbs_file->async_file = ev_file;
+		kref_get(&uverbs_file->async_file->ref);
+		INIT_IB_EVENT_HANDLER(&uverbs_file->event_handler,
+				      uverbs_file->device->ib_dev,
+				      ib_uverbs_event_handler);
+		ret = ib_register_event_handler(&uverbs_file->event_handler);
+		if (ret)
+			goto err_put_file;
+
+		/* At that point async file stuff was fully set */
+		ev_file->is_async = 1;
+	}
+
+	return filp;
+
+err_put_file:
+	fput(filp);
+	kref_put(&uverbs_file->async_file->ref, ib_uverbs_release_event_file);
+	uverbs_file->async_file = NULL;
+	return ERR_PTR(ret);
 
+err_put_refs:
+	kref_put(&ev_file->uverbs_file->ref, ib_uverbs_release_file);
+	kref_put(&ev_file->ref, ib_uverbs_release_event_file);
 	return filp;
 }
 
-- 
1.7.1

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[PATCH for-next V7 2/6] IB/uverbs: Fix race between ib_uverbs_open and remove_one

[Yishai Hadas]

Fixes: 2a72f212263701b927559f6850446421d5906c41 ("IB/uverbs: Remove dev_table")

Before this commit there was a device look-up table that was protected
by a spin_lock used by ib_uverbs_open and by ib_uverbs_remove_one. When
it was dropped and container_of was used instead, it enabled the race
with remove_one as dev might be freed just after:
dev = container_of(inode->i_cdev, struct ib_uverbs_device, cdev) but
before the kref_get.

In addition, this buggy patch added some dead code as
container_of(x,y,z) can never be NULL and so dev can never be NULL.
As a result the comment above ib_uverbs_open saying "the open method
will either immediately run -ENXIO" is wrong as it can never happen.

The solution follows Jason Gunthorpe suggestion from below URL:
https://www.mail-archive.com/linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org/msg25692.html

cdev will hold a kref on the parent (the containing structure,
ib_uverbs_device) and only when that kref is released it is
guaranteed that open will never be called again.

In addition, fixes the active count scheme to use an atomic
not a kref to prevent WARN_ON as pointed by above comment
from Jason.

Signed-off-by: Yishai Hadas <yishaih-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Signed-off-by: Shachar Raindel <raindel-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
---
 drivers/infiniband/core/uverbs.h      |    3 +-
 drivers/infiniband/core/uverbs_main.c |   43 +++++++++++++++++++++++----------
 2 files changed, 32 insertions(+), 14 deletions(-)

diff --git a/drivers/infiniband/core/uverbs.h b/drivers/infiniband/core/uverbs.h
index 60e6e3d..92ec765 100644
--- a/drivers/infiniband/core/uverbs.h
+++ b/drivers/infiniband/core/uverbs.h
@@ -85,7 +85,7 @@
  */
 
 struct ib_uverbs_device {
-	struct kref				ref;
+	atomic_t				refcount;
 	int					num_comp_vectors;
 	struct completion			comp;
 	struct device			       *dev;
@@ -94,6 +94,7 @@ struct ib_uverbs_device {
 	struct cdev			        cdev;
 	struct rb_root				xrcd_tree;
 	struct mutex				xrcd_tree_mutex;
+	struct kobject				kobj;
 };
 
 struct ib_uverbs_event_file {
diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
index c238eba..9f39978 100644
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -130,14 +130,18 @@ static int (*uverbs_ex_cmd_table[])(struct ib_uverbs_file *file,
 static void ib_uverbs_add_one(struct ib_device *device);
 static void ib_uverbs_remove_one(struct ib_device *device);
 
-static void ib_uverbs_release_dev(struct kref *ref)
+static void ib_uverbs_release_dev(struct kobject *kobj)
 {
 	struct ib_uverbs_device *dev =
-		container_of(ref, struct ib_uverbs_device, ref);
+		container_of(kobj, struct ib_uverbs_device, kobj);
 
-	complete(&dev->comp);
+	kfree(dev);
 }
 
+static struct kobj_type ib_uverbs_dev_ktype = {
+	.release = ib_uverbs_release_dev,
+};
+
 static void ib_uverbs_release_event_file(struct kref *ref)
 {
 	struct ib_uverbs_event_file *file =
@@ -303,13 +307,19 @@ static int ib_uverbs_cleanup_ucontext(struct ib_uverbs_file *file,
 	return context->device->dealloc_ucontext(context);
 }
 
+static void ib_uverbs_comp_dev(struct ib_uverbs_device *dev)
+{
+	complete(&dev->comp);
+}
+
 static void ib_uverbs_release_file(struct kref *ref)
 {
 	struct ib_uverbs_file *file =
 		container_of(ref, struct ib_uverbs_file, ref);
 
 	module_put(file->device->ib_dev->owner);
-	kref_put(&file->device->ref, ib_uverbs_release_dev);
+	if (atomic_dec_and_test(&file->device->refcount))
+		ib_uverbs_comp_dev(file->device);
 
 	kfree(file);
 }
@@ -775,9 +785,7 @@ static int ib_uverbs_open(struct inode *inode, struct file *filp)
 	int ret;
 
 	dev = container_of(inode->i_cdev, struct ib_uverbs_device, cdev);
-	if (dev)
-		kref_get(&dev->ref);
-	else
+	if (!atomic_inc_not_zero(&dev->refcount))
 		return -ENXIO;
 
 	if (!try_module_get(dev->ib_dev->owner)) {
@@ -798,6 +806,7 @@ static int ib_uverbs_open(struct inode *inode, struct file *filp)
 	mutex_init(&file->mutex);
 
 	filp->private_data = file;
+	kobject_get(&dev->kobj);
 
 	return nonseekable_open(inode, filp);
 
@@ -805,13 +814,16 @@ err_module:
 	module_put(dev->ib_dev->owner);
 
 err:
-	kref_put(&dev->ref, ib_uverbs_release_dev);
+	if (atomic_dec_and_test(&dev->refcount))
+		ib_uverbs_comp_dev(dev);
+
 	return ret;
 }
 
 static int ib_uverbs_close(struct inode *inode, struct file *filp)
 {
 	struct ib_uverbs_file *file = filp->private_data;
+	struct ib_uverbs_device *dev = file->device;
 
 	ib_uverbs_cleanup_ucontext(file, file->ucontext);
 
@@ -819,6 +831,7 @@ static int ib_uverbs_close(struct inode *inode, struct file *filp)
 		kref_put(&file->async_file->ref, ib_uverbs_release_event_file);
 
 	kref_put(&file->ref, ib_uverbs_release_file);
+	kobject_put(&dev->kobj);
 
 	return 0;
 }
@@ -914,10 +927,11 @@ static void ib_uverbs_add_one(struct ib_device *device)
 	if (!uverbs_dev)
 		return;
 
-	kref_init(&uverbs_dev->ref);
+	atomic_set(&uverbs_dev->refcount, 1);
 	init_completion(&uverbs_dev->comp);
 	uverbs_dev->xrcd_tree = RB_ROOT;
 	mutex_init(&uverbs_dev->xrcd_tree_mutex);
+	kobject_init(&uverbs_dev->kobj, &ib_uverbs_dev_ktype);
 
 	spin_lock(&map_lock);
 	devnum = find_first_zero_bit(dev_map, IB_UVERBS_MAX_DEVICES);
@@ -944,6 +958,7 @@ static void ib_uverbs_add_one(struct ib_device *device)
 	cdev_init(&uverbs_dev->cdev, NULL);
 	uverbs_dev->cdev.owner = THIS_MODULE;
 	uverbs_dev->cdev.ops = device->mmap ? &uverbs_mmap_fops : &uverbs_fops;
+	uverbs_dev->cdev.kobj.parent = &uverbs_dev->kobj;
 	kobject_set_name(&uverbs_dev->cdev.kobj, "uverbs%d", uverbs_dev->devnum);
 	if (cdev_add(&uverbs_dev->cdev, base, 1))
 		goto err_cdev;
@@ -974,9 +989,10 @@ err_cdev:
 		clear_bit(devnum, overflow_map);
 
 err:
-	kref_put(&uverbs_dev->ref, ib_uverbs_release_dev);
+	if (atomic_dec_and_test(&uverbs_dev->refcount))
+		ib_uverbs_comp_dev(uverbs_dev);
 	wait_for_completion(&uverbs_dev->comp);
-	kfree(uverbs_dev);
+	kobject_put(&uverbs_dev->kobj);
 	return;
 }
 
@@ -996,9 +1012,10 @@ static void ib_uverbs_remove_one(struct ib_device *device)
 	else
 		clear_bit(uverbs_dev->devnum - IB_UVERBS_MAX_DEVICES, overflow_map);
 
-	kref_put(&uverbs_dev->ref, ib_uverbs_release_dev);
+	if (atomic_dec_and_test(&uverbs_dev->refcount))
+		ib_uverbs_comp_dev(uverbs_dev);
 	wait_for_completion(&uverbs_dev->comp);
-	kfree(uverbs_dev);
+	kobject_put(&uverbs_dev->kobj);
 }
 
 static char *uverbs_devnode(struct device *dev, umode_t *mode)
-- 
1.7.1

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Re: [PATCH for-next V7 2/6] IB/uverbs: Fix race between ib_uverbs_open and remove_one

[Jason Gunthorpe]

On Tue, Aug 04, 2015 at 05:03:24PM +0300, Yishai Hadas wrote:

> Signed-off-by: Yishai Hadas <yishaih-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
> Signed-off-by: Shachar Raindel <raindel-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
>  drivers/infiniband/core/uverbs.h      |    3 +-
>  drivers/infiniband/core/uverbs_main.c |   43 +++++++++++++++++++++++----------
>  2 files changed, 32 insertions(+), 14 deletions(-)

This looks OK

Reviewed-by: Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>

> @@ -798,6 +806,7 @@ static int ib_uverbs_open(struct inode *inode, struct file *filp)
>  	mutex_init(&file->mutex);
>  
>  	filp->private_data = file;
> +	kobject_get(&dev->kobj);

Minor quibble, this and the matching put can be dropped. Seeing
container_of followed by a get with out a copy is a red flag to anyone
reading this code.

Jason
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[PATCH for-next V7 3/6] IB/uverbs: Explicitly pass ib_dev to uverbs commands

[Yishai Hadas]

Done in preparation for deploying RCU for the device removal
flow. Allows isolating the RCU handling to the uverb_main layer and
keeping the uverbs_cmd code as is.

Signed-off-by: Yishai Hadas <yishaih-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Signed-off-by: Shachar Raindel <raindel-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
---
 drivers/infiniband/core/uverbs.h      |    3 +
 drivers/infiniband/core/uverbs_cmd.c  |  103 ++++++++++++++++++++++-----------
 drivers/infiniband/core/uverbs_main.c |   21 +++++--
 3 files changed, 88 insertions(+), 39 deletions(-)

diff --git a/drivers/infiniband/core/uverbs.h b/drivers/infiniband/core/uverbs.h
index 92ec765..ea52db1 100644
--- a/drivers/infiniband/core/uverbs.h
+++ b/drivers/infiniband/core/uverbs.h
@@ -178,6 +178,7 @@ extern struct idr ib_uverbs_rule_idr;
 void idr_remove_uobj(struct idr *idp, struct ib_uobject *uobj);
 
 struct file *ib_uverbs_alloc_event_file(struct ib_uverbs_file *uverbs_file,
+					struct ib_device *ib_dev,
 					int is_async);
 void ib_uverbs_free_async_event_file(struct ib_uverbs_file *uverbs_file);
 struct ib_uverbs_event_file *ib_uverbs_lookup_comp_file(int fd);
@@ -214,6 +215,7 @@ struct ib_uverbs_flow_spec {
 
 #define IB_UVERBS_DECLARE_CMD(name)					\
 	ssize_t ib_uverbs_##name(struct ib_uverbs_file *file,		\
+				 struct ib_device *ib_dev,              \
 				 const char __user *buf, int in_len,	\
 				 int out_len)
 
@@ -255,6 +257,7 @@ IB_UVERBS_DECLARE_CMD(close_xrcd);
 
 #define IB_UVERBS_DECLARE_EX_CMD(name)				\
 	int ib_uverbs_ex_##name(struct ib_uverbs_file *file,	\
+				struct ib_device *ib_dev,		\
 				struct ib_udata *ucore,		\
 				struct ib_udata *uhw)
 
diff --git a/drivers/infiniband/core/uverbs_cmd.c b/drivers/infiniband/core/uverbs_cmd.c
index 5720a92..29443c0 100644
--- a/drivers/infiniband/core/uverbs_cmd.c
+++ b/drivers/infiniband/core/uverbs_cmd.c
@@ -282,13 +282,13 @@ static void put_xrcd_read(struct ib_uobject *uobj)
 }
 
 ssize_t ib_uverbs_get_context(struct ib_uverbs_file *file,
+			      struct ib_device *ib_dev,
 			      const char __user *buf,
 			      int in_len, int out_len)
 {
 	struct ib_uverbs_get_context      cmd;
 	struct ib_uverbs_get_context_resp resp;
 	struct ib_udata                   udata;
-	struct ib_device                 *ibdev = file->device->ib_dev;
 #ifdef CONFIG_INFINIBAND_ON_DEMAND_PAGING
 	struct ib_device_attr		  dev_attr;
 #endif
@@ -313,13 +313,13 @@ ssize_t ib_uverbs_get_context(struct ib_uverbs_file *file,
 		   (unsigned long) cmd.response + sizeof resp,
 		   in_len - sizeof cmd, out_len - sizeof resp);
 
-	ucontext = ibdev->alloc_ucontext(ibdev, &udata);
+	ucontext = ib_dev->alloc_ucontext(ib_dev, &udata);
 	if (IS_ERR(ucontext)) {
 		ret = PTR_ERR(ucontext);
 		goto err;
 	}
 
-	ucontext->device = ibdev;
+	ucontext->device = ib_dev;
 	INIT_LIST_HEAD(&ucontext->pd_list);
 	INIT_LIST_HEAD(&ucontext->mr_list);
 	INIT_LIST_HEAD(&ucontext->mw_list);
@@ -340,7 +340,7 @@ ssize_t ib_uverbs_get_context(struct ib_uverbs_file *file,
 	ucontext->odp_mrs_count = 0;
 	INIT_LIST_HEAD(&ucontext->no_private_counters);
 
-	ret = ib_query_device(ibdev, &dev_attr);
+	ret = ib_query_device(ib_dev, &dev_attr);
 	if (ret)
 		goto err_free;
 	if (!(dev_attr.device_cap_flags & IB_DEVICE_ON_DEMAND_PAGING))
@@ -355,7 +355,7 @@ ssize_t ib_uverbs_get_context(struct ib_uverbs_file *file,
 		goto err_free;
 	resp.async_fd = ret;
 
-	filp = ib_uverbs_alloc_event_file(file, 1);
+	filp = ib_uverbs_alloc_event_file(file, ib_dev, 1);
 	if (IS_ERR(filp)) {
 		ret = PTR_ERR(filp);
 		goto err_fd;
@@ -384,7 +384,7 @@ err_fd:
 
 err_free:
 	put_pid(ucontext->tgid);
-	ibdev->dealloc_ucontext(ucontext);
+	ib_dev->dealloc_ucontext(ucontext);
 
 err:
 	mutex_unlock(&file->mutex);
@@ -392,11 +392,12 @@ err:
 }
 
 static void copy_query_dev_fields(struct ib_uverbs_file *file,
+				  struct ib_device *ib_dev,
 				  struct ib_uverbs_query_device_resp *resp,
 				  struct ib_device_attr *attr)
 {
 	resp->fw_ver		= attr->fw_ver;
-	resp->node_guid		= file->device->ib_dev->node_guid;
+	resp->node_guid		= ib_dev->node_guid;
 	resp->sys_image_guid	= attr->sys_image_guid;
 	resp->max_mr_size	= attr->max_mr_size;
 	resp->page_size_cap	= attr->page_size_cap;
@@ -434,10 +435,11 @@ static void copy_query_dev_fields(struct ib_uverbs_file *file,
 	resp->max_srq_sge		= attr->max_srq_sge;
 	resp->max_pkeys			= attr->max_pkeys;
 	resp->local_ca_ack_delay	= attr->local_ca_ack_delay;
-	resp->phys_port_cnt		= file->device->ib_dev->phys_port_cnt;
+	resp->phys_port_cnt		= ib_dev->phys_port_cnt;
 }
 
 ssize_t ib_uverbs_query_device(struct ib_uverbs_file *file,
+			       struct ib_device *ib_dev,
 			       const char __user *buf,
 			       int in_len, int out_len)
 {
@@ -452,12 +454,12 @@ ssize_t ib_uverbs_query_device(struct ib_uverbs_file *file,
 	if (copy_from_user(&cmd, buf, sizeof cmd))
 		return -EFAULT;
 
-	ret = ib_query_device(file->device->ib_dev, &attr);
+	ret = ib_query_device(ib_dev, &attr);
 	if (ret)
 		return ret;
 
 	memset(&resp, 0, sizeof resp);
-	copy_query_dev_fields(file, &resp, &attr);
+	copy_query_dev_fields(file, ib_dev, &resp, &attr);
 
 	if (copy_to_user((void __user *) (unsigned long) cmd.response,
 			 &resp, sizeof resp))
@@ -467,6 +469,7 @@ ssize_t ib_uverbs_query_device(struct ib_uverbs_file *file,
 }
 
 ssize_t ib_uverbs_query_port(struct ib_uverbs_file *file,
+			     struct ib_device *ib_dev,
 			     const char __user *buf,
 			     int in_len, int out_len)
 {
@@ -481,7 +484,7 @@ ssize_t ib_uverbs_query_port(struct ib_uverbs_file *file,
 	if (copy_from_user(&cmd, buf, sizeof cmd))
 		return -EFAULT;
 
-	ret = ib_query_port(file->device->ib_dev, cmd.port_num, &attr);
+	ret = ib_query_port(ib_dev, cmd.port_num, &attr);
 	if (ret)
 		return ret;
 
@@ -506,7 +509,7 @@ ssize_t ib_uverbs_query_port(struct ib_uverbs_file *file,
 	resp.active_width    = attr.active_width;
 	resp.active_speed    = attr.active_speed;
 	resp.phys_state      = attr.phys_state;
-	resp.link_layer      = rdma_port_get_link_layer(file->device->ib_dev,
+	resp.link_layer      = rdma_port_get_link_layer(ib_dev,
 							cmd.port_num);
 
 	if (copy_to_user((void __user *) (unsigned long) cmd.response,
@@ -517,6 +520,7 @@ ssize_t ib_uverbs_query_port(struct ib_uverbs_file *file,
 }
 
 ssize_t ib_uverbs_alloc_pd(struct ib_uverbs_file *file,
+			   struct ib_device *ib_dev,
 			   const char __user *buf,
 			   int in_len, int out_len)
 {
@@ -544,14 +548,13 @@ ssize_t ib_uverbs_alloc_pd(struct ib_uverbs_file *file,
 	init_uobj(uobj, 0, file->ucontext, &pd_lock_class);
 	down_write(&uobj->mutex);
 
-	pd = file->device->ib_dev->alloc_pd(file->device->ib_dev,
-					    file->ucontext, &udata);
+	pd = ib_dev->alloc_pd(ib_dev, file->ucontext, &udata);
 	if (IS_ERR(pd)) {
 		ret = PTR_ERR(pd);
 		goto err;
 	}
 
-	pd->device  = file->device->ib_dev;
+	pd->device  = ib_dev;
 	pd->uobject = uobj;
 	atomic_set(&pd->usecnt, 0);
 
@@ -591,6 +594,7 @@ err:
 }
 
 ssize_t ib_uverbs_dealloc_pd(struct ib_uverbs_file *file,
+			     struct ib_device *ib_dev,
 			     const char __user *buf,
 			     int in_len, int out_len)
 {
@@ -711,6 +715,7 @@ static void xrcd_table_delete(struct ib_uverbs_device *dev,
 }
 
 ssize_t ib_uverbs_open_xrcd(struct ib_uverbs_file *file,
+			    struct ib_device *ib_dev,
 			    const char __user *buf, int in_len,
 			    int out_len)
 {
@@ -769,15 +774,14 @@ ssize_t ib_uverbs_open_xrcd(struct ib_uverbs_file *file,
 	down_write(&obj->uobject.mutex);
 
 	if (!xrcd) {
-		xrcd = file->device->ib_dev->alloc_xrcd(file->device->ib_dev,
-							file->ucontext, &udata);
+		xrcd = ib_dev->alloc_xrcd(ib_dev, file->ucontext, &udata);
 		if (IS_ERR(xrcd)) {
 			ret = PTR_ERR(xrcd);
 			goto err;
 		}
 
 		xrcd->inode   = inode;
-		xrcd->device  = file->device->ib_dev;
+		xrcd->device  = ib_dev;
 		atomic_set(&xrcd->usecnt, 0);
 		mutex_init(&xrcd->tgt_qp_mutex);
 		INIT_LIST_HEAD(&xrcd->tgt_qp_list);
@@ -848,6 +852,7 @@ err_tree_mutex_unlock:
 }
 
 ssize_t ib_uverbs_close_xrcd(struct ib_uverbs_file *file,
+			     struct ib_device *ib_dev,
 			     const char __user *buf, int in_len,
 			     int out_len)
 {
@@ -925,6 +930,7 @@ void ib_uverbs_dealloc_xrcd(struct ib_uverbs_device *dev,
 }
 
 ssize_t ib_uverbs_reg_mr(struct ib_uverbs_file *file,
+			 struct ib_device *ib_dev,
 			 const char __user *buf, int in_len,
 			 int out_len)
 {
@@ -1034,6 +1040,7 @@ err_free:
 }
 
 ssize_t ib_uverbs_rereg_mr(struct ib_uverbs_file *file,
+			   struct ib_device *ib_dev,
 			   const char __user *buf, int in_len,
 			   int out_len)
 {
@@ -1127,6 +1134,7 @@ put_uobjs:
 }
 
 ssize_t ib_uverbs_dereg_mr(struct ib_uverbs_file *file,
+			   struct ib_device *ib_dev,
 			   const char __user *buf, int in_len,
 			   int out_len)
 {
@@ -1165,8 +1173,9 @@ ssize_t ib_uverbs_dereg_mr(struct ib_uverbs_file *file,
 }
 
 ssize_t ib_uverbs_alloc_mw(struct ib_uverbs_file *file,
-			 const char __user *buf, int in_len,
-			 int out_len)
+			   struct ib_device *ib_dev,
+			   const char __user *buf, int in_len,
+			   int out_len)
 {
 	struct ib_uverbs_alloc_mw      cmd;
 	struct ib_uverbs_alloc_mw_resp resp;
@@ -1247,8 +1256,9 @@ err_free:
 }
 
 ssize_t ib_uverbs_dealloc_mw(struct ib_uverbs_file *file,
-			   const char __user *buf, int in_len,
-			   int out_len)
+			     struct ib_device *ib_dev,
+			     const char __user *buf, int in_len,
+			     int out_len)
 {
 	struct ib_uverbs_dealloc_mw cmd;
 	struct ib_mw               *mw;
@@ -1285,6 +1295,7 @@ ssize_t ib_uverbs_dealloc_mw(struct ib_uverbs_file *file,
 }
 
 ssize_t ib_uverbs_create_comp_channel(struct ib_uverbs_file *file,
+				      struct ib_device *ib_dev,
 				      const char __user *buf, int in_len,
 				      int out_len)
 {
@@ -1304,7 +1315,7 @@ ssize_t ib_uverbs_create_comp_channel(struct ib_uverbs_file *file,
 		return ret;
 	resp.fd = ret;
 
-	filp = ib_uverbs_alloc_event_file(file, 0);
+	filp = ib_uverbs_alloc_event_file(file, ib_dev, 0);
 	if (IS_ERR(filp)) {
 		put_unused_fd(resp.fd);
 		return PTR_ERR(filp);
@@ -1322,6 +1333,7 @@ ssize_t ib_uverbs_create_comp_channel(struct ib_uverbs_file *file,
 }
 
 static struct ib_ucq_object *create_cq(struct ib_uverbs_file *file,
+					struct ib_device *ib_dev,
 				       struct ib_udata *ucore,
 				       struct ib_udata *uhw,
 				       struct ib_uverbs_ex_create_cq *cmd,
@@ -1370,14 +1382,14 @@ static struct ib_ucq_object *create_cq(struct ib_uverbs_file *file,
 	if (cmd_sz > offsetof(typeof(*cmd), flags) + sizeof(cmd->flags))
 		attr.flags = cmd->flags;
 
-	cq = file->device->ib_dev->create_cq(file->device->ib_dev, &attr,
+	cq = ib_dev->create_cq(ib_dev, &attr,
 					     file->ucontext, uhw);
 	if (IS_ERR(cq)) {
 		ret = PTR_ERR(cq);
 		goto err_file;
 	}
 
-	cq->device        = file->device->ib_dev;
+	cq->device        = ib_dev;
 	cq->uobject       = &obj->uobject;
 	cq->comp_handler  = ib_uverbs_comp_handler;
 	cq->event_handler = ib_uverbs_cq_event_handler;
@@ -1438,6 +1450,7 @@ static int ib_uverbs_create_cq_cb(struct ib_uverbs_file *file,
 }
 
 ssize_t ib_uverbs_create_cq(struct ib_uverbs_file *file,
+			    struct ib_device *ib_dev,
 			    const char __user *buf, int in_len,
 			    int out_len)
 {
@@ -1466,7 +1479,7 @@ ssize_t ib_uverbs_create_cq(struct ib_uverbs_file *file,
 	cmd_ex.comp_vector = cmd.comp_vector;
 	cmd_ex.comp_channel = cmd.comp_channel;
 
-	obj = create_cq(file, &ucore, &uhw, &cmd_ex,
+	obj = create_cq(file, ib_dev, &ucore, &uhw, &cmd_ex,
 			offsetof(typeof(cmd_ex), comp_channel) +
 			sizeof(cmd.comp_channel), ib_uverbs_create_cq_cb,
 			NULL);
@@ -1489,6 +1502,7 @@ static int ib_uverbs_ex_create_cq_cb(struct ib_uverbs_file *file,
 }
 
 int ib_uverbs_ex_create_cq(struct ib_uverbs_file *file,
+			 struct ib_device *ib_dev,
 			   struct ib_udata *ucore,
 			   struct ib_udata *uhw)
 {
@@ -1514,7 +1528,7 @@ int ib_uverbs_ex_create_cq(struct ib_uverbs_file *file,
 			     sizeof(resp.response_length)))
 		return -ENOSPC;
 
-	obj = create_cq(file, ucore, uhw, &cmd,
+	obj = create_cq(file, ib_dev, ucore, uhw, &cmd,
 			min(ucore->inlen, sizeof(cmd)),
 			ib_uverbs_ex_create_cq_cb, NULL);
 
@@ -1525,6 +1539,7 @@ int ib_uverbs_ex_create_cq(struct ib_uverbs_file *file,
 }
 
 ssize_t ib_uverbs_resize_cq(struct ib_uverbs_file *file,
+			    struct ib_device *ib_dev,
 			    const char __user *buf, int in_len,
 			    int out_len)
 {
@@ -1588,6 +1603,7 @@ static int copy_wc_to_user(void __user *dest, struct ib_wc *wc)
 }
 
 ssize_t ib_uverbs_poll_cq(struct ib_uverbs_file *file,
+			  struct ib_device *ib_dev,
 			  const char __user *buf, int in_len,
 			  int out_len)
 {
@@ -1639,6 +1655,7 @@ out_put:
 }
 
 ssize_t ib_uverbs_req_notify_cq(struct ib_uverbs_file *file,
+				struct ib_device *ib_dev,
 				const char __user *buf, int in_len,
 				int out_len)
 {
@@ -1661,6 +1678,7 @@ ssize_t ib_uverbs_req_notify_cq(struct ib_uverbs_file *file,
 }
 
 ssize_t ib_uverbs_destroy_cq(struct ib_uverbs_file *file,
+			     struct ib_device *ib_dev,
 			     const char __user *buf, int in_len,
 			     int out_len)
 {
@@ -1713,6 +1731,7 @@ ssize_t ib_uverbs_destroy_cq(struct ib_uverbs_file *file,
 }
 
 ssize_t ib_uverbs_create_qp(struct ib_uverbs_file *file,
+			    struct ib_device *ib_dev,
 			    const char __user *buf, int in_len,
 			    int out_len)
 {
@@ -1908,6 +1927,7 @@ err_put:
 }
 
 ssize_t ib_uverbs_open_qp(struct ib_uverbs_file *file,
+			  struct ib_device *ib_dev,
 			  const char __user *buf, int in_len, int out_len)
 {
 	struct ib_uverbs_open_qp        cmd;
@@ -2002,6 +2022,7 @@ err_put:
 }
 
 ssize_t ib_uverbs_query_qp(struct ib_uverbs_file *file,
+			   struct ib_device *ib_dev,
 			   const char __user *buf, int in_len,
 			   int out_len)
 {
@@ -2116,6 +2137,7 @@ static int modify_qp_mask(enum ib_qp_type qp_type, int mask)
 }
 
 ssize_t ib_uverbs_modify_qp(struct ib_uverbs_file *file,
+			    struct ib_device *ib_dev,
 			    const char __user *buf, int in_len,
 			    int out_len)
 {
@@ -2212,6 +2234,7 @@ out:
 }
 
 ssize_t ib_uverbs_destroy_qp(struct ib_uverbs_file *file,
+			     struct ib_device *ib_dev,
 			     const char __user *buf, int in_len,
 			     int out_len)
 {
@@ -2270,6 +2293,7 @@ ssize_t ib_uverbs_destroy_qp(struct ib_uverbs_file *file,
 }
 
 ssize_t ib_uverbs_post_send(struct ib_uverbs_file *file,
+			    struct ib_device *ib_dev,
 			    const char __user *buf, int in_len,
 			    int out_len)
 {
@@ -2514,6 +2538,7 @@ err:
 }
 
 ssize_t ib_uverbs_post_recv(struct ib_uverbs_file *file,
+			    struct ib_device *ib_dev,
 			    const char __user *buf, int in_len,
 			    int out_len)
 {
@@ -2563,6 +2588,7 @@ out:
 }
 
 ssize_t ib_uverbs_post_srq_recv(struct ib_uverbs_file *file,
+				struct ib_device *ib_dev,
 				const char __user *buf, int in_len,
 				int out_len)
 {
@@ -2612,6 +2638,7 @@ out:
 }
 
 ssize_t ib_uverbs_create_ah(struct ib_uverbs_file *file,
+			    struct ib_device *ib_dev,
 			    const char __user *buf, int in_len,
 			    int out_len)
 {
@@ -2704,6 +2731,7 @@ err:
 }
 
 ssize_t ib_uverbs_destroy_ah(struct ib_uverbs_file *file,
+			     struct ib_device *ib_dev,
 			     const char __user *buf, int in_len, int out_len)
 {
 	struct ib_uverbs_destroy_ah cmd;
@@ -2740,6 +2768,7 @@ ssize_t ib_uverbs_destroy_ah(struct ib_uverbs_file *file,
 }
 
 ssize_t ib_uverbs_attach_mcast(struct ib_uverbs_file *file,
+			       struct ib_device *ib_dev,
 			       const char __user *buf, int in_len,
 			       int out_len)
 {
@@ -2787,6 +2816,7 @@ out_put:
 }
 
 ssize_t ib_uverbs_detach_mcast(struct ib_uverbs_file *file,
+			       struct ib_device *ib_dev,
 			       const char __user *buf, int in_len,
 			       int out_len)
 {
@@ -2867,6 +2897,7 @@ static int kern_spec_to_ib_spec(struct ib_uverbs_flow_spec *kern_spec,
 }
 
 int ib_uverbs_ex_create_flow(struct ib_uverbs_file *file,
+			     struct ib_device *ib_dev,
 			     struct ib_udata *ucore,
 			     struct ib_udata *uhw)
 {
@@ -3027,6 +3058,7 @@ err_free_attr:
 }
 
 int ib_uverbs_ex_destroy_flow(struct ib_uverbs_file *file,
+			      struct ib_device *ib_dev,
 			      struct ib_udata *ucore,
 			      struct ib_udata *uhw)
 {
@@ -3069,6 +3101,7 @@ int ib_uverbs_ex_destroy_flow(struct ib_uverbs_file *file,
 }
 
 static int __uverbs_create_xsrq(struct ib_uverbs_file *file,
+				struct ib_device *ib_dev,
 				struct ib_uverbs_create_xsrq *cmd,
 				struct ib_udata *udata)
 {
@@ -3202,6 +3235,7 @@ err:
 }
 
 ssize_t ib_uverbs_create_srq(struct ib_uverbs_file *file,
+			     struct ib_device *ib_dev,
 			     const char __user *buf, int in_len,
 			     int out_len)
 {
@@ -3229,7 +3263,7 @@ ssize_t ib_uverbs_create_srq(struct ib_uverbs_file *file,
 		   (unsigned long) cmd.response + sizeof resp,
 		   in_len - sizeof cmd, out_len - sizeof resp);
 
-	ret = __uverbs_create_xsrq(file, &xcmd, &udata);
+	ret = __uverbs_create_xsrq(file, ib_dev, &xcmd, &udata);
 	if (ret)
 		return ret;
 
@@ -3237,6 +3271,7 @@ ssize_t ib_uverbs_create_srq(struct ib_uverbs_file *file,
 }
 
 ssize_t ib_uverbs_create_xsrq(struct ib_uverbs_file *file,
+			      struct ib_device *ib_dev,
 			      const char __user *buf, int in_len, int out_len)
 {
 	struct ib_uverbs_create_xsrq     cmd;
@@ -3254,7 +3289,7 @@ ssize_t ib_uverbs_create_xsrq(struct ib_uverbs_file *file,
 		   (unsigned long) cmd.response + sizeof resp,
 		   in_len - sizeof cmd, out_len - sizeof resp);
 
-	ret = __uverbs_create_xsrq(file, &cmd, &udata);
+	ret = __uverbs_create_xsrq(file, ib_dev, &cmd, &udata);
 	if (ret)
 		return ret;
 
@@ -3262,6 +3297,7 @@ ssize_t ib_uverbs_create_xsrq(struct ib_uverbs_file *file,
 }
 
 ssize_t ib_uverbs_modify_srq(struct ib_uverbs_file *file,
+			     struct ib_device *ib_dev,
 			     const char __user *buf, int in_len,
 			     int out_len)
 {
@@ -3292,6 +3328,7 @@ ssize_t ib_uverbs_modify_srq(struct ib_uverbs_file *file,
 }
 
 ssize_t ib_uverbs_query_srq(struct ib_uverbs_file *file,
+			    struct ib_device *ib_dev,
 			    const char __user *buf,
 			    int in_len, int out_len)
 {
@@ -3332,6 +3369,7 @@ ssize_t ib_uverbs_query_srq(struct ib_uverbs_file *file,
 }
 
 ssize_t ib_uverbs_destroy_srq(struct ib_uverbs_file *file,
+			      struct ib_device *ib_dev,
 			      const char __user *buf, int in_len,
 			      int out_len)
 {
@@ -3389,16 +3427,15 @@ ssize_t ib_uverbs_destroy_srq(struct ib_uverbs_file *file,
 }
 
 int ib_uverbs_ex_query_device(struct ib_uverbs_file *file,
+			      struct ib_device *ib_dev,
 			      struct ib_udata *ucore,
 			      struct ib_udata *uhw)
 {
 	struct ib_uverbs_ex_query_device_resp resp;
 	struct ib_uverbs_ex_query_device  cmd;
 	struct ib_device_attr attr;
-	struct ib_device *device;
 	int err;
 
-	device = file->device->ib_dev;
 	if (ucore->inlen < sizeof(cmd))
 		return -EINVAL;
 
@@ -3419,11 +3456,11 @@ int ib_uverbs_ex_query_device(struct ib_uverbs_file *file,
 
 	memset(&attr, 0, sizeof(attr));
 
-	err = device->query_device(device, &attr, uhw);
+	err = ib_dev->query_device(ib_dev, &attr, uhw);
 	if (err)
 		return err;
 
-	copy_query_dev_fields(file, &resp.base, &attr);
+	copy_query_dev_fields(file, ib_dev, &resp.base, &attr);
 	resp.comp_mask = 0;
 
 	if (ucore->outlen < resp.response_length + sizeof(resp.odp_caps))
diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
index 9f39978..dc968df 100644
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -79,6 +79,7 @@ static DEFINE_SPINLOCK(map_lock);
 static DECLARE_BITMAP(dev_map, IB_UVERBS_MAX_DEVICES);
 
 static ssize_t (*uverbs_cmd_table[])(struct ib_uverbs_file *file,
+				     struct ib_device *ib_dev,
 				     const char __user *buf, int in_len,
 				     int out_len) = {
 	[IB_USER_VERBS_CMD_GET_CONTEXT]		= ib_uverbs_get_context,
@@ -119,6 +120,7 @@ static ssize_t (*uverbs_cmd_table[])(struct ib_uverbs_file *file,
 };
 
 static int (*uverbs_ex_cmd_table[])(struct ib_uverbs_file *file,
+				    struct ib_device *ib_dev,
 				    struct ib_udata *ucore,
 				    struct ib_udata *uhw) = {
 	[IB_USER_VERBS_EX_CMD_CREATE_FLOW]	= ib_uverbs_ex_create_flow,
@@ -557,6 +559,7 @@ void ib_uverbs_free_async_event_file(struct ib_uverbs_file *file)
 }
 
 struct file *ib_uverbs_alloc_event_file(struct ib_uverbs_file *uverbs_file,
+					struct ib_device	*ib_dev,
 					int is_async)
 {
 	struct ib_uverbs_event_file *ev_file;
@@ -586,7 +589,7 @@ struct file *ib_uverbs_alloc_event_file(struct ib_uverbs_file *uverbs_file,
 		uverbs_file->async_file = ev_file;
 		kref_get(&uverbs_file->async_file->ref);
 		INIT_IB_EVENT_HANDLER(&uverbs_file->event_handler,
-				      uverbs_file->device->ib_dev,
+				      ib_dev,
 				      ib_uverbs_event_handler);
 		ret = ib_register_event_handler(&uverbs_file->event_handler);
 		if (ret)
@@ -643,9 +646,13 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf,
 			     size_t count, loff_t *pos)
 {
 	struct ib_uverbs_file *file = filp->private_data;
+	struct ib_device *ib_dev = file->device->ib_dev;
 	struct ib_uverbs_cmd_hdr hdr;
 	__u32 flags;
 
+	if (!ib_dev)
+		return -ENODEV;
+
 	if (count < sizeof hdr)
 		return -EINVAL;
 
@@ -672,13 +679,13 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf,
 		    command != IB_USER_VERBS_CMD_GET_CONTEXT)
 			return -EINVAL;
 
-		if (!(file->device->ib_dev->uverbs_cmd_mask & (1ull << command)))
+		if (!(ib_dev->uverbs_cmd_mask & (1ull << command)))
 			return -ENOSYS;
 
 		if (hdr.in_words * 4 != count)
 			return -EINVAL;
 
-		return uverbs_cmd_table[command](file,
+		return uverbs_cmd_table[command](file, ib_dev,
 						 buf + sizeof(hdr),
 						 hdr.in_words * 4,
 						 hdr.out_words * 4);
@@ -705,7 +712,7 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf,
 		if (!file->ucontext)
 			return -EINVAL;
 
-		if (!(file->device->ib_dev->uverbs_ex_cmd_mask & (1ull << command)))
+		if (!(ib_dev->uverbs_ex_cmd_mask & (1ull << command)))
 			return -ENOSYS;
 
 		if (count < (sizeof(hdr) + sizeof(ex_hdr)))
@@ -746,6 +753,7 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf,
 				       ex_hdr.provider_out_words * 8);
 
 		err = uverbs_ex_cmd_table[command](file,
+						   ib_dev,
 						   &ucore,
 						   &uhw);
 
@@ -761,11 +769,12 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf,
 static int ib_uverbs_mmap(struct file *filp, struct vm_area_struct *vma)
 {
 	struct ib_uverbs_file *file = filp->private_data;
+	struct ib_device *ib_dev = file->device->ib_dev;
 
-	if (!file->ucontext)
+	if (!ib_dev || !file->ucontext)
 		return -ENODEV;
 	else
-		return file->device->ib_dev->mmap(file->ucontext, vma);
+		return ib_dev->mmap(file->ucontext, vma);
 }
 
 /*
-- 
1.7.1

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[PATCH for-next V7 4/6] IB/uverbs: Enable device removal when there are active user space applications

[Yishai Hadas]

Enables the uverbs_remove_one to succeed despite the fact that there are
running IB applications working with the given ib device.  This
functionality enables a HW device to be unbind/reset despite the fact that
there are running user space applications using it.

It exposes a new IB kernel API named 'disassociate_ucontext' which lets
a driver detaching its HW resources from a given user context without
crashing/terminating the application. In case a driver implemented the
above API and registered with ib_uverb there will be no dependency between its
device to its uverbs_device. Upon calling remove_one of ib_uverbs the call
should return after disassociating the open HW resources without waiting to
clients disconnecting. In case driver didn't implement this API there will be no
change to current behaviour and uverbs_remove_one will return only when last
client has disconnected and reference count on uverbs device became 0.

In case the lower driver device was removed any application will
continue working over some zombie HCA, further calls will ended with an
immediate error.

Signed-off-by: Yishai Hadas <yishaih-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Signed-off-by: Shachar Raindel <raindel-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
---
 drivers/infiniband/core/uverbs.h      |    9 +-
 drivers/infiniband/core/uverbs_main.c |  360 +++++++++++++++++++++++++++------
 include/rdma/ib_verbs.h               |    1 +
 3 files changed, 302 insertions(+), 68 deletions(-)

diff --git a/drivers/infiniband/core/uverbs.h b/drivers/infiniband/core/uverbs.h
index ea52db1..3863d33 100644
--- a/drivers/infiniband/core/uverbs.h
+++ b/drivers/infiniband/core/uverbs.h
@@ -89,12 +89,16 @@ struct ib_uverbs_device {
 	int					num_comp_vectors;
 	struct completion			comp;
 	struct device			       *dev;
-	struct ib_device		       *ib_dev;
+	struct ib_device	__rcu	       *ib_dev;
 	int					devnum;
 	struct cdev			        cdev;
 	struct rb_root				xrcd_tree;
 	struct mutex				xrcd_tree_mutex;
 	struct kobject				kobj;
+	struct srcu_struct			disassociate_srcu;
+	struct mutex				lists_mutex; /* protect lists */
+	struct list_head			uverbs_file_list;
+	struct list_head			uverbs_events_file_list;
 };
 
 struct ib_uverbs_event_file {
@@ -106,6 +110,7 @@ struct ib_uverbs_event_file {
 	wait_queue_head_t			poll_wait;
 	struct fasync_struct		       *async_queue;
 	struct list_head			event_list;
+	struct list_head			list;
 };
 
 struct ib_uverbs_file {
@@ -115,6 +120,8 @@ struct ib_uverbs_file {
 	struct ib_ucontext		       *ucontext;
 	struct ib_event_handler			event_handler;
 	struct ib_uverbs_event_file	       *async_file;
+	struct list_head			list;
+	int					is_closed;
 };
 
 struct ib_uverbs_event {
diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
index dc968df..59b28a6 100644
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -137,6 +137,7 @@ static void ib_uverbs_release_dev(struct kobject *kobj)
 	struct ib_uverbs_device *dev =
 		container_of(kobj, struct ib_uverbs_device, kobj);
 
+	cleanup_srcu_struct(&dev->disassociate_srcu);
 	kfree(dev);
 }
 
@@ -207,9 +208,6 @@ static int ib_uverbs_cleanup_ucontext(struct ib_uverbs_file *file,
 {
 	struct ib_uobject *uobj, *tmp;
 
-	if (!context)
-		return 0;
-
 	context->closing = 1;
 
 	list_for_each_entry_safe(uobj, tmp, &context->ah_list, list) {
@@ -318,8 +316,16 @@ static void ib_uverbs_release_file(struct kref *ref)
 {
 	struct ib_uverbs_file *file =
 		container_of(ref, struct ib_uverbs_file, ref);
+	struct ib_device *ib_dev;
+	int srcu_key;
+
+	srcu_key = srcu_read_lock(&file->device->disassociate_srcu);
+	ib_dev = srcu_dereference(file->device->ib_dev,
+				  &file->device->disassociate_srcu);
+	if (ib_dev && !ib_dev->disassociate_ucontext)
+		module_put(ib_dev->owner);
+	srcu_read_unlock(&file->device->disassociate_srcu, srcu_key);
 
-	module_put(file->device->ib_dev->owner);
 	if (atomic_dec_and_test(&file->device->refcount))
 		ib_uverbs_comp_dev(file->device);
 
@@ -343,9 +349,19 @@ static ssize_t ib_uverbs_event_read(struct file *filp, char __user *buf,
 			return -EAGAIN;
 
 		if (wait_event_interruptible(file->poll_wait,
-					     !list_empty(&file->event_list)))
+					     (!list_empty(&file->event_list) ||
+			/* The barriers built into wait_event_interruptible()
+			 * and wake_up() guarentee this will see the null set
+			 * without using RCU
+			 */
+					     !file->uverbs_file->device->ib_dev)))
 			return -ERESTARTSYS;
 
+		/* If device was disassociated and no event exists set an error */
+		if (list_empty(&file->event_list) &&
+		    !file->uverbs_file->device->ib_dev)
+			return -EIO;
+
 		spin_lock_irq(&file->lock);
 	}
 
@@ -408,8 +424,11 @@ static int ib_uverbs_event_close(struct inode *inode, struct file *filp)
 {
 	struct ib_uverbs_event_file *file = filp->private_data;
 	struct ib_uverbs_event *entry, *tmp;
+	int closed_already = 0;
 
+	mutex_lock(&file->uverbs_file->device->lists_mutex);
 	spin_lock_irq(&file->lock);
+	closed_already = file->is_closed;
 	file->is_closed = 1;
 	list_for_each_entry_safe(entry, tmp, &file->event_list, list) {
 		if (entry->counter)
@@ -417,9 +436,14 @@ static int ib_uverbs_event_close(struct inode *inode, struct file *filp)
 		kfree(entry);
 	}
 	spin_unlock_irq(&file->lock);
+	if (!closed_already) {
+		list_del(&file->list);
+		if (file->is_async)
+			ib_unregister_event_handler(&file->uverbs_file->
+				event_handler);
+	}
+	mutex_unlock(&file->uverbs_file->device->lists_mutex);
 
-	if (file->is_async)
-		ib_unregister_event_handler(&file->uverbs_file->event_handler);
 	kref_put(&file->uverbs_file->ref, ib_uverbs_release_file);
 	kref_put(&file->ref, ib_uverbs_release_event_file);
 
@@ -584,6 +608,11 @@ struct file *ib_uverbs_alloc_event_file(struct ib_uverbs_file *uverbs_file,
 	if (IS_ERR(filp))
 		goto err_put_refs;
 
+	mutex_lock(&uverbs_file->device->lists_mutex);
+	list_add_tail(&ev_file->list,
+		      &uverbs_file->device->uverbs_events_file_list);
+	mutex_unlock(&uverbs_file->device->lists_mutex);
+
 	if (is_async) {
 		WARN_ON(uverbs_file->async_file);
 		uverbs_file->async_file = ev_file;
@@ -646,12 +675,11 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf,
 			     size_t count, loff_t *pos)
 {
 	struct ib_uverbs_file *file = filp->private_data;
-	struct ib_device *ib_dev = file->device->ib_dev;
+	struct ib_device *ib_dev;
 	struct ib_uverbs_cmd_hdr hdr;
 	__u32 flags;
-
-	if (!ib_dev)
-		return -ENODEV;
+	int srcu_key;
+	ssize_t ret;
 
 	if (count < sizeof hdr)
 		return -EINVAL;
@@ -659,6 +687,14 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf,
 	if (copy_from_user(&hdr, buf, sizeof hdr))
 		return -EFAULT;
 
+	srcu_key = srcu_read_lock(&file->device->disassociate_srcu);
+	ib_dev = srcu_dereference(file->device->ib_dev,
+				  &file->device->disassociate_srcu);
+	if (!ib_dev) {
+		ret = -EIO;
+		goto out;
+	}
+
 	flags = (hdr.command &
 		 IB_USER_VERBS_CMD_FLAGS_MASK) >> IB_USER_VERBS_CMD_FLAGS_SHIFT;
 
@@ -666,26 +702,36 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf,
 		__u32 command;
 
 		if (hdr.command & ~(__u32)(IB_USER_VERBS_CMD_FLAGS_MASK |
-					   IB_USER_VERBS_CMD_COMMAND_MASK))
-			return -EINVAL;
+					   IB_USER_VERBS_CMD_COMMAND_MASK)) {
+			ret = -EINVAL;
+			goto out;
+		}
 
 		command = hdr.command & IB_USER_VERBS_CMD_COMMAND_MASK;
 
 		if (command >= ARRAY_SIZE(uverbs_cmd_table) ||
-		    !uverbs_cmd_table[command])
-			return -EINVAL;
+		    !uverbs_cmd_table[command]) {
+			ret = -EINVAL;
+			goto out;
+		}
 
 		if (!file->ucontext &&
-		    command != IB_USER_VERBS_CMD_GET_CONTEXT)
-			return -EINVAL;
+		    command != IB_USER_VERBS_CMD_GET_CONTEXT) {
+			ret = -EINVAL;
+			goto out;
+		}
 
-		if (!(ib_dev->uverbs_cmd_mask & (1ull << command)))
-			return -ENOSYS;
+		if (!(ib_dev->uverbs_cmd_mask & (1ull << command))) {
+			ret = -ENOSYS;
+			goto out;
+		}
 
-		if (hdr.in_words * 4 != count)
-			return -EINVAL;
+		if (hdr.in_words * 4 != count) {
+			ret = -EINVAL;
+			goto out;
+		}
 
-		return uverbs_cmd_table[command](file, ib_dev,
+		ret = uverbs_cmd_table[command](file, ib_dev,
 						 buf + sizeof(hdr),
 						 hdr.in_words * 4,
 						 hdr.out_words * 4);
@@ -696,51 +742,72 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf,
 		struct ib_uverbs_ex_cmd_hdr ex_hdr;
 		struct ib_udata ucore;
 		struct ib_udata uhw;
-		int err;
 		size_t written_count = count;
 
 		if (hdr.command & ~(__u32)(IB_USER_VERBS_CMD_FLAGS_MASK |
-					   IB_USER_VERBS_CMD_COMMAND_MASK))
-			return -EINVAL;
+					   IB_USER_VERBS_CMD_COMMAND_MASK)) {
+			ret = -EINVAL;
+			goto out;
+		}
 
 		command = hdr.command & IB_USER_VERBS_CMD_COMMAND_MASK;
 
 		if (command >= ARRAY_SIZE(uverbs_ex_cmd_table) ||
-		    !uverbs_ex_cmd_table[command])
-			return -ENOSYS;
+		    !uverbs_ex_cmd_table[command]) {
+			ret = -ENOSYS;
+			goto out;
+		}
 
-		if (!file->ucontext)
-			return -EINVAL;
+		if (!file->ucontext) {
+			ret = -EINVAL;
+			goto out;
+		}
 
-		if (!(ib_dev->uverbs_ex_cmd_mask & (1ull << command)))
-			return -ENOSYS;
+		if (!(ib_dev->uverbs_ex_cmd_mask & (1ull << command))) {
+			ret = -ENOSYS;
+			goto out;
+		}
 
-		if (count < (sizeof(hdr) + sizeof(ex_hdr)))
-			return -EINVAL;
+		if (count < (sizeof(hdr) + sizeof(ex_hdr))) {
+			ret = -EINVAL;
+			goto out;
+		}
 
-		if (copy_from_user(&ex_hdr, buf + sizeof(hdr), sizeof(ex_hdr)))
-			return -EFAULT;
+		if (copy_from_user(&ex_hdr, buf + sizeof(hdr), sizeof(ex_hdr))) {
+			ret = -EFAULT;
+			goto out;
+		}
 
 		count -= sizeof(hdr) + sizeof(ex_hdr);
 		buf += sizeof(hdr) + sizeof(ex_hdr);
 
-		if ((hdr.in_words + ex_hdr.provider_in_words) * 8 != count)
-			return -EINVAL;
+		if ((hdr.in_words + ex_hdr.provider_in_words) * 8 != count) {
+			ret = -EINVAL;
+			goto out;
+		}
 
-		if (ex_hdr.cmd_hdr_reserved)
-			return -EINVAL;
+		if (ex_hdr.cmd_hdr_reserved) {
+			ret = -EINVAL;
+			goto out;
+		}
 
 		if (ex_hdr.response) {
-			if (!hdr.out_words && !ex_hdr.provider_out_words)
-				return -EINVAL;
+			if (!hdr.out_words && !ex_hdr.provider_out_words) {
+				ret = -EINVAL;
+				goto out;
+			}
 
 			if (!access_ok(VERIFY_WRITE,
 				       (void __user *) (unsigned long) ex_hdr.response,
-				       (hdr.out_words + ex_hdr.provider_out_words) * 8))
-				return -EFAULT;
+				       (hdr.out_words + ex_hdr.provider_out_words) * 8)) {
+				ret = -EFAULT;
+				goto out;
+			}
 		} else {
-			if (hdr.out_words || ex_hdr.provider_out_words)
-				return -EINVAL;
+			if (hdr.out_words || ex_hdr.provider_out_words) {
+				ret = -EINVAL;
+				goto out;
+			}
 		}
 
 		INIT_UDATA_BUF_OR_NULL(&ucore, buf, (unsigned long) ex_hdr.response,
@@ -752,29 +819,43 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf,
 				       ex_hdr.provider_in_words * 8,
 				       ex_hdr.provider_out_words * 8);
 
-		err = uverbs_ex_cmd_table[command](file,
+		ret = uverbs_ex_cmd_table[command](file,
 						   ib_dev,
 						   &ucore,
 						   &uhw);
-
-		if (err)
-			return err;
-
-		return written_count;
+		if (!ret)
+			ret = written_count;
+	} else {
+		ret = -ENOSYS;
 	}
 
-	return -ENOSYS;
+out:
+	srcu_read_unlock(&file->device->disassociate_srcu, srcu_key);
+	return ret;
 }
 
 static int ib_uverbs_mmap(struct file *filp, struct vm_area_struct *vma)
 {
 	struct ib_uverbs_file *file = filp->private_data;
-	struct ib_device *ib_dev = file->device->ib_dev;
+	struct ib_device *ib_dev;
+	int ret = 0;
+	int srcu_key;
 
-	if (!ib_dev || !file->ucontext)
-		return -ENODEV;
+	srcu_key = srcu_read_lock(&file->device->disassociate_srcu);
+	ib_dev = srcu_dereference(file->device->ib_dev,
+				  &file->device->disassociate_srcu);
+	if (!ib_dev) {
+		ret = -EIO;
+		goto out;
+	}
+
+	if (!file->ucontext)
+		ret = -ENODEV;
 	else
-		return ib_dev->mmap(file->ucontext, vma);
+		ret = ib_dev->mmap(file->ucontext, vma);
+out:
+	srcu_read_unlock(&file->device->disassociate_srcu, srcu_key);
+	return ret;
 }
 
 /*
@@ -791,21 +872,43 @@ static int ib_uverbs_open(struct inode *inode, struct file *filp)
 {
 	struct ib_uverbs_device *dev;
 	struct ib_uverbs_file *file;
+	struct ib_device *ib_dev;
 	int ret;
+	int module_dependent;
+	int srcu_key;
 
 	dev = container_of(inode->i_cdev, struct ib_uverbs_device, cdev);
 	if (!atomic_inc_not_zero(&dev->refcount))
 		return -ENXIO;
 
-	if (!try_module_get(dev->ib_dev->owner)) {
-		ret = -ENODEV;
+	srcu_key = srcu_read_lock(&dev->disassociate_srcu);
+	mutex_lock(&dev->lists_mutex);
+	ib_dev = srcu_dereference(dev->ib_dev,
+				  &dev->disassociate_srcu);
+	if (!ib_dev) {
+		ret = -EIO;
 		goto err;
 	}
 
-	file = kmalloc(sizeof *file, GFP_KERNEL);
+	/* In case IB device supports disassociate ucontext, there is no hard
+	 * dependency between uverbs device and its low level device.
+	 */
+	module_dependent = !(ib_dev->disassociate_ucontext);
+
+	if (module_dependent) {
+		if (!try_module_get(ib_dev->owner)) {
+			ret = -ENODEV;
+			goto err;
+		}
+	}
+
+	file = kzalloc(sizeof(*file), GFP_KERNEL);
 	if (!file) {
 		ret = -ENOMEM;
-		goto err_module;
+		if (module_dependent)
+			goto err_module;
+
+		goto err;
 	}
 
 	file->device	 = dev;
@@ -816,13 +919,18 @@ static int ib_uverbs_open(struct inode *inode, struct file *filp)
 
 	filp->private_data = file;
 	kobject_get(&dev->kobj);
+	list_add_tail(&file->list, &dev->uverbs_file_list);
+	mutex_unlock(&dev->lists_mutex);
+	srcu_read_unlock(&dev->disassociate_srcu, srcu_key);
 
 	return nonseekable_open(inode, filp);
 
 err_module:
-	module_put(dev->ib_dev->owner);
+	module_put(ib_dev->owner);
 
 err:
+	mutex_unlock(&dev->lists_mutex);
+	srcu_read_unlock(&dev->disassociate_srcu, srcu_key);
 	if (atomic_dec_and_test(&dev->refcount))
 		ib_uverbs_comp_dev(dev);
 
@@ -833,8 +941,18 @@ static int ib_uverbs_close(struct inode *inode, struct file *filp)
 {
 	struct ib_uverbs_file *file = filp->private_data;
 	struct ib_uverbs_device *dev = file->device;
-
-	ib_uverbs_cleanup_ucontext(file, file->ucontext);
+	struct ib_ucontext *ucontext = NULL;
+
+	mutex_lock(&file->device->lists_mutex);
+	ucontext = file->ucontext;
+	file->ucontext = NULL;
+	if (!file->is_closed) {
+		list_del(&file->list);
+		file->is_closed = 1;
+	}
+	mutex_unlock(&file->device->lists_mutex);
+	if (ucontext)
+		ib_uverbs_cleanup_ucontext(file, ucontext);
 
 	if (file->async_file)
 		kref_put(&file->async_file->ref, ib_uverbs_release_event_file);
@@ -871,12 +989,21 @@ static struct ib_client uverbs_client = {
 static ssize_t show_ibdev(struct device *device, struct device_attribute *attr,
 			  char *buf)
 {
+	int ret = -ENODEV;
+	int srcu_key;
 	struct ib_uverbs_device *dev = dev_get_drvdata(device);
+	struct ib_device *ib_dev;
 
 	if (!dev)
 		return -ENODEV;
 
-	return sprintf(buf, "%s\n", dev->ib_dev->name);
+	srcu_key = srcu_read_lock(&dev->disassociate_srcu);
+	ib_dev = srcu_dereference(dev->ib_dev, &dev->disassociate_srcu);
+	if (ib_dev)
+		ret = sprintf(buf, "%s\n", ib_dev->name);
+	srcu_read_unlock(&dev->disassociate_srcu, srcu_key);
+
+	return ret;
 }
 static DEVICE_ATTR(ibdev, S_IRUGO, show_ibdev, NULL);
 
@@ -884,11 +1011,19 @@ static ssize_t show_dev_abi_version(struct device *device,
 				    struct device_attribute *attr, char *buf)
 {
 	struct ib_uverbs_device *dev = dev_get_drvdata(device);
+	int ret = -ENODEV;
+	int srcu_key;
+	struct ib_device *ib_dev;
 
 	if (!dev)
 		return -ENODEV;
+	srcu_key = srcu_read_lock(&dev->disassociate_srcu);
+	ib_dev = srcu_dereference(dev->ib_dev, &dev->disassociate_srcu);
+	if (ib_dev)
+		ret = sprintf(buf, "%d\n", ib_dev->uverbs_abi_ver);
+	srcu_read_unlock(&dev->disassociate_srcu, srcu_key);
 
-	return sprintf(buf, "%d\n", dev->ib_dev->uverbs_abi_ver);
+	return ret;
 }
 static DEVICE_ATTR(abi_version, S_IRUGO, show_dev_abi_version, NULL);
 
@@ -928,6 +1063,7 @@ static void ib_uverbs_add_one(struct ib_device *device)
 	int devnum;
 	dev_t base;
 	struct ib_uverbs_device *uverbs_dev;
+	int ret;
 
 	if (!device->alloc_ucontext)
 		return;
@@ -936,11 +1072,20 @@ static void ib_uverbs_add_one(struct ib_device *device)
 	if (!uverbs_dev)
 		return;
 
+	ret = init_srcu_struct(&uverbs_dev->disassociate_srcu);
+	if (ret) {
+		kfree(uverbs_dev);
+		return;
+	}
+
 	atomic_set(&uverbs_dev->refcount, 1);
 	init_completion(&uverbs_dev->comp);
 	uverbs_dev->xrcd_tree = RB_ROOT;
 	mutex_init(&uverbs_dev->xrcd_tree_mutex);
 	kobject_init(&uverbs_dev->kobj, &ib_uverbs_dev_ktype);
+	mutex_init(&uverbs_dev->lists_mutex);
+	INIT_LIST_HEAD(&uverbs_dev->uverbs_file_list);
+	INIT_LIST_HEAD(&uverbs_dev->uverbs_events_file_list);
 
 	spin_lock(&map_lock);
 	devnum = find_first_zero_bit(dev_map, IB_UVERBS_MAX_DEVICES);
@@ -961,7 +1106,7 @@ static void ib_uverbs_add_one(struct ib_device *device)
 	}
 	spin_unlock(&map_lock);
 
-	uverbs_dev->ib_dev           = device;
+	rcu_assign_pointer(uverbs_dev->ib_dev, device);
 	uverbs_dev->num_comp_vectors = device->num_comp_vectors;
 
 	cdev_init(&uverbs_dev->cdev, NULL);
@@ -1005,9 +1150,72 @@ err:
 	return;
 }
 
+static void ib_uverbs_free_hw_resources(struct ib_uverbs_device *uverbs_dev,
+					struct ib_device *ib_dev)
+{
+	struct ib_uverbs_file *file;
+	struct ib_uverbs_event_file *event_file;
+	struct ib_event event;
+
+	/* Pending running commands to terminate */
+	synchronize_srcu(&uverbs_dev->disassociate_srcu);
+	event.event = IB_EVENT_DEVICE_FATAL;
+	event.element.port_num = 0;
+	event.device = ib_dev;
+
+	mutex_lock(&uverbs_dev->lists_mutex);
+	while (!list_empty(&uverbs_dev->uverbs_file_list)) {
+		struct ib_ucontext *ucontext;
+
+		file = list_first_entry(&uverbs_dev->uverbs_file_list,
+					struct ib_uverbs_file, list);
+		file->is_closed = 1;
+		ucontext = file->ucontext;
+		list_del(&file->list);
+		file->ucontext = NULL;
+		kref_get(&file->ref);
+		mutex_unlock(&uverbs_dev->lists_mutex);
+		/* We must release the mutex before going ahead and calling
+		 * disassociate_ucontext. disassociate_ucontext might end up
+		 * indirectly calling uverbs_close, for example due to freeing
+		 * the resources (e.g mmput).
+		 */
+		ib_uverbs_event_handler(&file->event_handler, &event);
+		if (ucontext) {
+			ib_dev->disassociate_ucontext(ucontext);
+			ib_uverbs_cleanup_ucontext(file, ucontext);
+		}
+
+		mutex_lock(&uverbs_dev->lists_mutex);
+		kref_put(&file->ref, ib_uverbs_release_file);
+	}
+
+	while (!list_empty(&uverbs_dev->uverbs_events_file_list)) {
+		event_file = list_first_entry(&uverbs_dev->
+					      uverbs_events_file_list,
+					      struct ib_uverbs_event_file,
+					      list);
+		spin_lock_irq(&event_file->lock);
+		event_file->is_closed = 1;
+		spin_unlock_irq(&event_file->lock);
+
+		list_del(&event_file->list);
+		if (event_file->is_async) {
+			ib_unregister_event_handler(&event_file->uverbs_file->
+						    event_handler);
+			event_file->uverbs_file->event_handler.device = NULL;
+		}
+
+		wake_up_interruptible(&event_file->poll_wait);
+		kill_fasync(&event_file->async_queue, SIGIO, POLL_IN);
+	}
+	mutex_unlock(&uverbs_dev->lists_mutex);
+}
+
 static void ib_uverbs_remove_one(struct ib_device *device)
 {
 	struct ib_uverbs_device *uverbs_dev = ib_get_client_data(device, &uverbs_client);
+	int wait_clients = 1;
 
 	if (!uverbs_dev)
 		return;
@@ -1021,9 +1229,27 @@ static void ib_uverbs_remove_one(struct ib_device *device)
 	else
 		clear_bit(uverbs_dev->devnum - IB_UVERBS_MAX_DEVICES, overflow_map);
 
+	if (device->disassociate_ucontext) {
+		/* We disassociate HW resources and immediately return.
+		 * Userspace will see a EIO errno for all future access.
+		 * Upon returning, ib_device may be freed internally and is not
+		 * valid any more.
+		 * uverbs_device is still available until all clients close
+		 * their files, then the uverbs device ref count will be zero
+		 * and its resources will be freed.
+		 * Note: At this point no more files can be opened since the
+		 * cdev was deleted, however active clients can still issue
+		 * commands and close their open files.
+		 */
+		rcu_assign_pointer(uverbs_dev->ib_dev, NULL);
+		ib_uverbs_free_hw_resources(uverbs_dev, device);
+		wait_clients = 0;
+	}
+
 	if (atomic_dec_and_test(&uverbs_dev->refcount))
 		ib_uverbs_comp_dev(uverbs_dev);
-	wait_for_completion(&uverbs_dev->comp);
+	if (wait_clients)
+		wait_for_completion(&uverbs_dev->comp);
 	kobject_put(&uverbs_dev->kobj);
 }
 
diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index b0f898e..4f21d72 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -1724,6 +1724,7 @@ struct ib_device {
 	int			   (*destroy_flow)(struct ib_flow *flow_id);
 	int			   (*check_mr_status)(struct ib_mr *mr, u32 check_mask,
 						      struct ib_mr_status *mr_status);
+	void			   (*disassociate_ucontext)(struct ib_ucontext *ibcontext);
 
 	struct ib_dma_mapping_ops   *dma_ops;
 
-- 
1.7.1

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Re: [PATCH for-next V7 4/6] IB/uverbs: Enable device removal when there are active user space applications

[Jason Gunthorpe]

On Tue, Aug 04, 2015 at 05:03:26PM +0300, Yishai Hadas wrote:
> Enables the uverbs_remove_one to succeed despite the fact that there are
> running IB applications working with the given ib device.  This
> functionality enables a HW device to be unbind/reset despite the fact that
> there are running user space applications using it.
> 
> It exposes a new IB kernel API named 'disassociate_ucontext' which lets
> a driver detaching its HW resources from a given user context without
> crashing/terminating the application. In case a driver implemented the
> above API and registered with ib_uverb there will be no dependency between its
> device to its uverbs_device. Upon calling remove_one of ib_uverbs the call
> should return after disassociating the open HW resources without waiting to
> clients disconnecting. In case driver didn't implement this API there will be no
> change to current behaviour and uverbs_remove_one will return only when last
> client has disconnected and reference count on uverbs device became 0.
> 
> In case the lower driver device was removed any application will
> continue working over some zombie HCA, further calls will ended with an
> immediate error.

Looks OK now..

Reviewed-by: Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>

I think I provided reviews for 1-4 now, you forgot the copy them
forward from v6 to help Doug.

Jason
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[PATCH for-next V7 5/6] IB/mlx4_ib: Disassociate support

[Yishai Hadas]

Implements the IB core disassociate_ucontext API. The driver detaches the HW
resources for a given user context to prevent a dependency between application
termination and device disconnecting. This is done by managing the VMAs that
were mapped to the HW bars such as door bell and blueflame. When need to detach
remap them to an arbitrary kernel page returned by the zap API.

Signed-off-by: Yishai Hadas <yishaih-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Signed-off-by: Jack Morgenstein <jackm-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
---
 drivers/infiniband/hw/mlx4/main.c    |  139 +++++++++++++++++++++++++++++++++-
 drivers/infiniband/hw/mlx4/mlx4_ib.h |   13 +++
 2 files changed, 150 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/hw/mlx4/main.c b/drivers/infiniband/hw/mlx4/main.c
index 8be6db8..3097a27 100644
--- a/drivers/infiniband/hw/mlx4/main.c
+++ b/drivers/infiniband/hw/mlx4/main.c
@@ -692,7 +692,7 @@ static struct ib_ucontext *mlx4_ib_alloc_ucontext(struct ib_device *ibdev,
 		resp.cqe_size	      = dev->dev->caps.cqe_size;
 	}
 
-	context = kmalloc(sizeof *context, GFP_KERNEL);
+	context = kzalloc(sizeof(*context), GFP_KERNEL);
 	if (!context)
 		return ERR_PTR(-ENOMEM);
 
@@ -729,21 +729,143 @@ static int mlx4_ib_dealloc_ucontext(struct ib_ucontext *ibcontext)
 	return 0;
 }
 
+static void  mlx4_ib_vma_open(struct vm_area_struct *area)
+{
+	/* vma_open is called when a new VMA is created on top of our VMA.
+	 * This is done through either mremap flow or split_vma (usually due
+	 * to mlock, madvise, munmap, etc.). We do not support a clone of the
+	 * vma, as this VMA is strongly hardware related. Therefore we set the
+	 * vm_ops of the newly created/cloned VMA to NULL, to prevent it from
+	 * calling us again and trying to do incorrect actions. We assume that
+	 * the original vma size is exactly a single page that there will be no
+	 * "splitting" operations on.
+	 */
+	area->vm_ops = NULL;
+}
+
+static void  mlx4_ib_vma_close(struct vm_area_struct *area)
+{
+	struct mlx4_ib_vma_private_data *mlx4_ib_vma_priv_data;
+
+	/* It's guaranteed that all VMAs opened on a FD are closed before the
+	 * file itself is closed, therefore no sync is needed with the regular
+	 * closing flow. (e.g. mlx4_ib_dealloc_ucontext) However need a sync
+	 * with accessing the vma as part of mlx4_ib_disassociate_ucontext.
+	 * The close operation is usually called under mm->mmap_sem except when
+	 * process is exiting.  The exiting case is handled explicitly as part
+	 * of mlx4_ib_disassociate_ucontext.
+	 */
+	mlx4_ib_vma_priv_data = (struct mlx4_ib_vma_private_data *)
+				area->vm_private_data;
+
+	/* set the vma context pointer to null in the mlx4_ib driver's private
+	 * data to protect against a race condition in mlx4_ib_dissassociate_ucontext().
+	 */
+	mlx4_ib_vma_priv_data->vma = NULL;
+}
+
+static const struct vm_operations_struct mlx4_ib_vm_ops = {
+	.open = mlx4_ib_vma_open,
+	.close = mlx4_ib_vma_close
+};
+
+static void mlx4_ib_disassociate_ucontext(struct ib_ucontext *ibcontext)
+{
+	int i;
+	int ret = 0;
+	struct vm_area_struct *vma;
+	struct mlx4_ib_ucontext *context = to_mucontext(ibcontext);
+	struct task_struct *owning_process  = NULL;
+	struct mm_struct   *owning_mm       = NULL;
+
+	owning_process = get_pid_task(ibcontext->tgid, PIDTYPE_PID);
+	if (!owning_process)
+		return;
+
+	owning_mm = get_task_mm(owning_process);
+	if (!owning_mm) {
+		pr_info("no mm, disassociate ucontext is pending task termination\n");
+		while (1) {
+			/* make sure that task is dead before returning, it may
+			 * prevent a rare case of module down in parallel to a
+			 * call to mlx4_ib_vma_close.
+			 */
+			put_task_struct(owning_process);
+			msleep(1);
+			owning_process = get_pid_task(ibcontext->tgid,
+						      PIDTYPE_PID);
+			if (!owning_process ||
+			    owning_process->state == TASK_DEAD) {
+				pr_info("disassociate ucontext done, task was terminated\n");
+				/* in case task was dead need to release the task struct */
+				if (owning_process)
+					put_task_struct(owning_process);
+				return;
+			}
+		}
+	}
+
+	/* need to protect from a race on closing the vma as part of
+	 * mlx4_ib_vma_close().
+	 */
+	down_read(&owning_mm->mmap_sem);
+	for (i = 0; i < HW_BAR_COUNT; i++) {
+		vma = context->hw_bar_info[i].vma;
+		if (!vma)
+			continue;
+
+		ret = zap_vma_ptes(context->hw_bar_info[i].vma,
+				   context->hw_bar_info[i].vma->vm_start,
+				   PAGE_SIZE);
+		if (ret) {
+			pr_err("Error: zap_vma_ptes failed for index=%d, ret=%d\n", i, ret);
+			BUG_ON(1);
+		}
+
+		/* context going to be destroyed, should not access ops any more */
+		context->hw_bar_info[i].vma->vm_ops = NULL;
+	}
+
+	up_read(&owning_mm->mmap_sem);
+	mmput(owning_mm);
+	put_task_struct(owning_process);
+}
+
+static void mlx4_ib_set_vma_data(struct vm_area_struct *vma,
+				 struct mlx4_ib_vma_private_data *vma_private_data)
+{
+	vma_private_data->vma = vma;
+	vma->vm_private_data = vma_private_data;
+	vma->vm_ops =  &mlx4_ib_vm_ops;
+}
+
 static int mlx4_ib_mmap(struct ib_ucontext *context, struct vm_area_struct *vma)
 {
 	struct mlx4_ib_dev *dev = to_mdev(context->device);
+	struct mlx4_ib_ucontext *mucontext = to_mucontext(context);
 
 	if (vma->vm_end - vma->vm_start != PAGE_SIZE)
 		return -EINVAL;
 
 	if (vma->vm_pgoff == 0) {
+		/* We prevent double mmaping on same context */
+		if (mucontext->hw_bar_info[HW_BAR_DB].vma)
+			return -EINVAL;
+
 		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 
 		if (io_remap_pfn_range(vma, vma->vm_start,
 				       to_mucontext(context)->uar.pfn,
 				       PAGE_SIZE, vma->vm_page_prot))
 			return -EAGAIN;
+
+		mlx4_ib_set_vma_data(vma, &mucontext->hw_bar_info[HW_BAR_DB]);
+
 	} else if (vma->vm_pgoff == 1 && dev->dev->caps.bf_reg_size != 0) {
+		/* We prevent double mmaping on same context */
+		if (mucontext->hw_bar_info[HW_BAR_BF].vma)
+			return -EINVAL;
+
 		vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
 
 		if (io_remap_pfn_range(vma, vma->vm_start,
@@ -751,9 +873,18 @@ static int mlx4_ib_mmap(struct ib_ucontext *context, struct vm_area_struct *vma)
 				       dev->dev->caps.num_uars,
 				       PAGE_SIZE, vma->vm_page_prot))
 			return -EAGAIN;
+
+		mlx4_ib_set_vma_data(vma, &mucontext->hw_bar_info[HW_BAR_BF]);
+
 	} else if (vma->vm_pgoff == 3) {
 		struct mlx4_clock_params params;
-		int ret = mlx4_get_internal_clock_params(dev->dev, &params);
+		int ret;
+
+		/* We prevent double mmaping on same context */
+		if (mucontext->hw_bar_info[HW_BAR_CLOCK].vma)
+			return -EINVAL;
+
+		ret = mlx4_get_internal_clock_params(dev->dev, &params);
 
 		if (ret)
 			return ret;
@@ -766,6 +897,9 @@ static int mlx4_ib_mmap(struct ib_ucontext *context, struct vm_area_struct *vma)
 				       >> PAGE_SHIFT,
 				       PAGE_SIZE, vma->vm_page_prot))
 			return -EAGAIN;
+
+		mlx4_ib_set_vma_data(vma,
+				     &mucontext->hw_bar_info[HW_BAR_CLOCK]);
 	} else {
 		return -EINVAL;
 	}
@@ -2300,6 +2434,7 @@ static void *mlx4_ib_add(struct mlx4_dev *dev)
 	ibdev->ib_dev.detach_mcast	= mlx4_ib_mcg_detach;
 	ibdev->ib_dev.process_mad	= mlx4_ib_process_mad;
 	ibdev->ib_dev.get_port_immutable = mlx4_port_immutable;
+	ibdev->ib_dev.disassociate_ucontext = mlx4_ib_disassociate_ucontext;
 
 	if (!mlx4_is_slave(ibdev->dev)) {
 		ibdev->ib_dev.alloc_fmr		= mlx4_ib_fmr_alloc;
diff --git a/drivers/infiniband/hw/mlx4/mlx4_ib.h b/drivers/infiniband/hw/mlx4/mlx4_ib.h
index 334387f..4eb7a85 100644
--- a/drivers/infiniband/hw/mlx4/mlx4_ib.h
+++ b/drivers/infiniband/hw/mlx4/mlx4_ib.h
@@ -70,11 +70,24 @@ extern int mlx4_ib_sm_guid_assign;
 
 #define MLX4_IB_UC_STEER_QPN_ALIGN 1
 #define MLX4_IB_UC_MAX_NUM_QPS     256
+
+enum hw_bar_type {
+	HW_BAR_BF,
+	HW_BAR_DB,
+	HW_BAR_CLOCK,
+	HW_BAR_COUNT
+};
+
+struct mlx4_ib_vma_private_data {
+	struct vm_area_struct *vma;
+};
+
 struct mlx4_ib_ucontext {
 	struct ib_ucontext	ibucontext;
 	struct mlx4_uar		uar;
 	struct list_head	db_page_list;
 	struct mutex		db_page_mutex;
+	struct mlx4_ib_vma_private_data hw_bar_info[HW_BAR_COUNT];
 };
 
 struct mlx4_ib_pd {
-- 
1.7.1

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[PATCH for-next V7 6/6] IB/ucma: HW Device hot-removal support

[Yishai Hadas]

Currently, IB/cma remove_one flow blocks until all user descriptor managed by
IB/ucma are released. This prevents hot-removal of IB devices. This patch
allows IB/cma to remove devices regardless of user space activity. Upon getting
the RDMA_CM_EVENT_DEVICE_REMOVAL event we close all the underlying HW resources
for the given ucontext. The ucontext itself is still alive till its explicit
destroying by its creator.

Running applications at that time will have some zombie device, further
operations may fail.

Signed-off-by: Yishai Hadas <yishaih-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Signed-off-by: Shachar Raindel <raindel-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
---
 drivers/infiniband/core/ucma.c |  130 ++++++++++++++++++++++++++++++++++++----
 1 files changed, 119 insertions(+), 11 deletions(-)

diff --git a/drivers/infiniband/core/ucma.c b/drivers/infiniband/core/ucma.c
index 29b2121..e9037df 100644
--- a/drivers/infiniband/core/ucma.c
+++ b/drivers/infiniband/core/ucma.c
@@ -74,6 +74,7 @@ struct ucma_file {
 	struct list_head	ctx_list;
 	struct list_head	event_list;
 	wait_queue_head_t	poll_wait;
+	struct workqueue_struct	*close_wq;
 };
 
 struct ucma_context {
@@ -89,6 +90,9 @@ struct ucma_context {
 
 	struct list_head	list;
 	struct list_head	mc_list;
+	int			closing;
+	int			destroying;
+	struct work_struct	close_work;
 };
 
 struct ucma_multicast {
@@ -107,6 +111,7 @@ struct ucma_event {
 	struct list_head	list;
 	struct rdma_cm_id	*cm_id;
 	struct rdma_ucm_event_resp resp;
+	struct work_struct	close_work;
 };
 
 static DEFINE_MUTEX(mut);
@@ -132,8 +137,12 @@ static struct ucma_context *ucma_get_ctx(struct ucma_file *file, int id)
 
 	mutex_lock(&mut);
 	ctx = _ucma_find_context(id, file);
-	if (!IS_ERR(ctx))
-		atomic_inc(&ctx->ref);
+	if (!IS_ERR(ctx)) {
+		if (ctx->closing)
+			ctx = ERR_PTR(-EIO);
+		else
+			atomic_inc(&ctx->ref);
+	}
 	mutex_unlock(&mut);
 	return ctx;
 }
@@ -144,6 +153,34 @@ static void ucma_put_ctx(struct ucma_context *ctx)
 		complete(&ctx->comp);
 }
 
+static void ucma_close_event_id(struct work_struct *work)
+{
+	struct ucma_event *uevent_close =  container_of(work, struct ucma_event, close_work);
+
+	rdma_destroy_id(uevent_close->cm_id);
+	kfree(uevent_close);
+}
+
+static void ucma_close_id(struct work_struct *work)
+{
+	struct ucma_context *ctx =  container_of(work, struct ucma_context, close_work);
+
+	/* Fence to ensure that ctx->closing was seen by all
+	 * ucma_get_ctx running
+	 */
+	mutex_lock(&mut);
+	mutex_unlock(&mut);
+
+	/* once all inflight tasks are finished, we close all underlying
+	 * resources. The context is still alive till its explicit destryoing
+	 * by its creator.
+	 */
+	ucma_put_ctx(ctx);
+	wait_for_completion(&ctx->comp);
+	/* No new events will be generated after destroying the id. */
+	rdma_destroy_id(ctx->cm_id);
+}
+
 static struct ucma_context *ucma_alloc_ctx(struct ucma_file *file)
 {
 	struct ucma_context *ctx;
@@ -152,6 +189,7 @@ static struct ucma_context *ucma_alloc_ctx(struct ucma_file *file)
 	if (!ctx)
 		return NULL;
 
+	INIT_WORK(&ctx->close_work, ucma_close_id);
 	atomic_set(&ctx->ref, 1);
 	init_completion(&ctx->comp);
 	INIT_LIST_HEAD(&ctx->mc_list);
@@ -242,6 +280,42 @@ static void ucma_set_event_context(struct ucma_context *ctx,
 	}
 }
 
+/* Called with file->mut locked for the relevant context. */
+static void ucma_removal_event_handler(struct rdma_cm_id *cm_id)
+{
+	struct ucma_context *ctx = cm_id->context;
+	struct ucma_event *con_req_eve;
+	int event_found = 0;
+
+	if (ctx->destroying)
+		return;
+
+	/* only if context is pointing to cm_id that it owns it and can be
+	 * queued to be closed, otherwise that cm_id is an inflight one that
+	 * is part of that context event list pending to be detached and
+	 * reattached to its new context as part of ucma_get_event,
+	 * handled separately below.
+	 */
+	if (ctx->cm_id == cm_id) {
+		ctx->closing = 1;
+		queue_work(ctx->file->close_wq, &ctx->close_work);
+		return;
+	}
+
+	list_for_each_entry(con_req_eve, &ctx->file->event_list, list) {
+		if (con_req_eve->cm_id == cm_id &&
+		    con_req_eve->resp.event == RDMA_CM_EVENT_CONNECT_REQUEST) {
+			list_del(&con_req_eve->list);
+			INIT_WORK(&con_req_eve->close_work, ucma_close_event_id);
+			queue_work(ctx->file->close_wq, &con_req_eve->close_work);
+			event_found = 1;
+			break;
+		}
+	}
+	if (!event_found)
+		printk(KERN_ERR "ucma_removal_event_handler: warning: connect request event wasn't found\n");
+}
+
 static int ucma_event_handler(struct rdma_cm_id *cm_id,
 			      struct rdma_cm_event *event)
 {
@@ -276,14 +350,21 @@ static int ucma_event_handler(struct rdma_cm_id *cm_id,
 		 * We ignore events for new connections until userspace has set
 		 * their context.  This can only happen if an error occurs on a
 		 * new connection before the user accepts it.  This is okay,
-		 * since the accept will just fail later.
+		 * since the accept will just fail later. However, we do need
+		 * to release the underlying HW resources in case of a device
+		 * removal event.
 		 */
+		if (event->event == RDMA_CM_EVENT_DEVICE_REMOVAL)
+			ucma_removal_event_handler(cm_id);
+
 		kfree(uevent);
 		goto out;
 	}
 
 	list_add_tail(&uevent->list, &ctx->file->event_list);
 	wake_up_interruptible(&ctx->file->poll_wait);
+	if (event->event == RDMA_CM_EVENT_DEVICE_REMOVAL)
+		ucma_removal_event_handler(cm_id);
 out:
 	mutex_unlock(&ctx->file->mut);
 	return ret;
@@ -442,9 +523,15 @@ static void ucma_cleanup_mc_events(struct ucma_multicast *mc)
 }
 
 /*
- * We cannot hold file->mut when calling rdma_destroy_id() or we can
- * deadlock.  We also acquire file->mut in ucma_event_handler(), and
- * rdma_destroy_id() will wait until all callbacks have completed.
+ * ucma_free_ctx is called after the underlying rdma CM-ID is destroyed. At
+ * this point, no new events will be reported from the hardware. However, we
+ * still need to cleanup the UCMA context for this ID. Specifically, there
+ * might be events that have not yet been consumed by the user space software.
+ * These might include pending connect requests which we have not completed
+ * processing.  We cannot call rdma_destroy_id while holding the lock of the
+ * context (file->mut), as it might cause a deadlock. We therefore extract all
+ * relevant events from the context pending events list while holding the
+ * mutex. After that we release them as needed.
  */
 static int ucma_free_ctx(struct ucma_context *ctx)
 {
@@ -452,8 +539,6 @@ static int ucma_free_ctx(struct ucma_context *ctx)
 	struct ucma_event *uevent, *tmp;
 	LIST_HEAD(list);
 
-	/* No new events will be generated after destroying the id. */
-	rdma_destroy_id(ctx->cm_id);
 
 	ucma_cleanup_multicast(ctx);
 
@@ -501,10 +586,20 @@ static ssize_t ucma_destroy_id(struct ucma_file *file, const char __user *inbuf,
 	if (IS_ERR(ctx))
 		return PTR_ERR(ctx);
 
-	ucma_put_ctx(ctx);
-	wait_for_completion(&ctx->comp);
-	resp.events_reported = ucma_free_ctx(ctx);
+	mutex_lock(&ctx->file->mut);
+	ctx->destroying = 1;
+	mutex_unlock(&ctx->file->mut);
+
+	flush_workqueue(ctx->file->close_wq);
+	/* At this point it's guaranteed that there is no inflight
+	 * closing task */
+	if (!ctx->closing) {
+		ucma_put_ctx(ctx);
+		wait_for_completion(&ctx->comp);
+		rdma_destroy_id(ctx->cm_id);
+	}
 
+	resp.events_reported = ucma_free_ctx(ctx);
 	if (copy_to_user((void __user *)(unsigned long)cmd.response,
 			 &resp, sizeof(resp)))
 		ret = -EFAULT;
@@ -1529,6 +1624,7 @@ static int ucma_open(struct inode *inode, struct file *filp)
 	INIT_LIST_HEAD(&file->ctx_list);
 	init_waitqueue_head(&file->poll_wait);
 	mutex_init(&file->mut);
+	file->close_wq = create_singlethread_workqueue("ucma_close_id");
 
 	filp->private_data = file;
 	file->filp = filp;
@@ -1543,16 +1639,28 @@ static int ucma_close(struct inode *inode, struct file *filp)
 
 	mutex_lock(&file->mut);
 	list_for_each_entry_safe(ctx, tmp, &file->ctx_list, list) {
+		ctx->destroying = 1;
 		mutex_unlock(&file->mut);
 
 		mutex_lock(&mut);
 		idr_remove(&ctx_idr, ctx->id);
 		mutex_unlock(&mut);
 
+		flush_workqueue(file->close_wq);
+		/* At that step once ctx was marked as destroying and workqueue
+		 * was flushed we are safe from any inflights handlers that
+		 * might put other closing task.
+		 */
+		if (!ctx->closing)
+			/* rdma_destroy_id ensures that no event handlers are
+			 * inflight for that id before releasing it.
+			 */
+			rdma_destroy_id(ctx->cm_id);
 		ucma_free_ctx(ctx);
 		mutex_lock(&file->mut);
 	}
 	mutex_unlock(&file->mut);
+	destroy_workqueue(file->close_wq);
 	kfree(file);
 	return 0;
 }
-- 
1.7.1

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Re: [PATCH for-next V7 6/6] IB/ucma: HW Device hot-removal support

[Jason Gunthorpe]

On Tue, Aug 04, 2015 at 05:03:28PM +0300, Yishai Hadas wrote:
> Currently, IB/cma remove_one flow blocks until all user descriptor managed by
> IB/ucma are released. This prevents hot-removal of IB devices. This patch
> allows IB/cma to remove devices regardless of user space activity. Upon getting
> the RDMA_CM_EVENT_DEVICE_REMOVAL event we close all the underlying HW resources
> for the given ucontext. The ucontext itself is still alive till its explicit
> destroying by its creator.
> 
> Running applications at that time will have some zombie device, further
> operations may fail.

I've never made it far enough to look at this patch before... It is
Sean's stuff so he is best qualified to comment on it. The rest of the
series is OK now Sean.

> +static void ucma_close_id(struct work_struct *work)
> +{
> +	struct ucma_context *ctx =  container_of(work, struct ucma_context, close_work);
> +
> +	/* Fence to ensure that ctx->closing was seen by all
> +	 * ucma_get_ctx running
> +	 */
> +	mutex_lock(&mut);
> +	mutex_unlock(&mut);

Uh, no. That isn't how to use mutex's.

I don't really see any consistent locking scheme for closing..

Jason
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Re: [PATCH for-next V7 6/6] IB/ucma: HW Device hot-removal support

[Yishai Hadas]

On 8/5/2015 1:09 AM, Jason Gunthorpe wrote:
> On Tue, Aug 04, 2015 at 05:03:28PM +0300, Yishai Hadas wrote:
>> Currently, IB/cma remove_one flow blocks until all user descriptor managed by
>> IB/ucma are released. This prevents hot-removal of IB devices. This patch
>> allows IB/cma to remove devices regardless of user space activity. Upon getting
>> the RDMA_CM_EVENT_DEVICE_REMOVAL event we close all the underlying HW resources
>> for the given ucontext. The ucontext itself is still alive till its explicit
>> destroying by its creator.
>>
>> Running applications at that time will have some zombie device, further
>> operations may fail.
>
> I've never made it far enough to look at this patch before... It is
> Sean's stuff so he is best qualified to comment on it. The rest of the
> series is OK now Sean.
>
>> +static void ucma_close_id(struct work_struct *work)
>> +{
>> +	struct ucma_context *ctx =  container_of(work, struct ucma_context, close_work);
>> +
>> +	/* Fence to ensure that ctx->closing was seen by all
>> +	 * ucma_get_ctx running
>> +	 */
>> +	mutex_lock(&mut);
>> +	mutex_unlock(&mut);
>
> Uh, no. That isn't how to use mutex's.

That locking scheme is used in some other places in the kernel when a 
barrier/fence is needed, see below some examples of that usage and my 
comment around the usage.

One of (see below in cma.c) was added by Sean Hefty as part of commit ID 
a396d43a in rdma_destroy_id, it's part of same kernel subsystem and uses 
same concept as of above code.

I believe that we can go ahead and merge this patch as part of the series.

If you still don't agree we can go ahead and merge the first 5 patches 
that doesn't depend on that last patch and handle/discuss this patch later.

The first 4 you already review and acked the fifth is in mlx4_ib and has 
no comments to fix so far - some months in the list.


Some examples of that usage:
------------------------------
http://lxr.free-electrons.com/source/kernel/audit.c#L532
         /* wait for parent to finish and send an ACK */
532         mutex_lock(&audit_cmd_mutex);
533         mutex_unlock(&audit_cmd_mutex);

http://lxr.free-electrons.com/source/fs/configfs/dir.c#L1386
1386                         /* Wait until the racing operation 
terminates */
1387                         mutex_lock(wait_mutex);
1388                         mutex_unlock(wait_mutex);

http://lxr.free-electrons.com/source/drivers/infiniband/core/cma.c#L1053
1050          /* Wait for any active callback to finish.  New callbacks 
will find
1051          * the id_priv state set to destroying and abort.
1052          */
1053         mutex_lock(&id_priv->handler_mutex);
1054         mutex_unlock(&id_priv->handler_mutex);

http://lxr.free-electrons.com/source/drivers/staging/lustre/lustre/ptlrpc/sec_gc.c#L96
  96         /* barrier */
  97         mutex_lock(&sec_gc_mutex);
  98         mutex_unlock(&sec_gc_mutex);


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Re: [PATCH for-next V7 6/6] IB/ucma: HW Device hot-removal support

[Jason Gunthorpe]

On Wed, Aug 05, 2015 at 06:09:45PM +0300, Yishai Hadas wrote:
> >>+static void ucma_close_id(struct work_struct *work)
> >>+{
> >>+	struct ucma_context *ctx =  container_of(work, struct ucma_context, close_work);
> >>+
> >>+	/* Fence to ensure that ctx->closing was seen by all
> >>+	 * ucma_get_ctx running
> >>+	 */
> >>+	mutex_lock(&mut);
> >>+	mutex_unlock(&mut);
> >
> >Uh, no. That isn't how to use mutex's.
> 
> That locking scheme is used in some other places in the kernel when a
> barrier/fence is needed, see below some examples of that usage and my
> comment around the usage.

'I saw it used someplace else' isn't much of an argument.. Maybe those
places are sane, this isn't so much..

> If you still don't agree we can go ahead and merge the first 5 patches that
> doesn't depend on that last patch and handle/discuss this patch later.

I have no real problem with that, it would be nice to have an answer
to the uverbs vs ucma removal ordering question and the basic issue of
if we even want to do this so async before merging the driver patch
that enables it..

> The first 4 you already review and acked the fifth is in mlx4_ib and has no
> comments to fix so far - some months in the list.

Personally, I'm not looking much at drivers..

Jason
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RE: [PATCH for-next V7 6/6] IB/ucma: HW Device hot-removal support

[Liran Liss]

> From: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org [mailto:linux-rdma-
> owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org] On Behalf Of Jason Gunthorpe
> 
> I have no real problem with that, it would be nice to have an answer
> to the uverbs vs ucma removal ordering question and the basic issue of
> if we even want to do this so async before merging the driver patch
> that enables it..
> 

I don't think that the order matters.
When you do a surprise removal, you disconnect the application from both ucma and uverbs device references.
In this state, the only thing that the application can do is close all handles.
It doesn't matter if you succeed closing a resource on a device that is still accessible, or "close" an already destroyed resource...

The primary reason for device surprise removal is to recover from device fatal errors or PCI errors.
A quick asynchronous device recovery is exactly what we need, as there is nothing that the application can do more at this state.
This is the most pressing issue that this patch-set solves.

For the administrative removal use case, can consider providing applications a grace period before disconnecting them in a future patch set.
Even here, however, I am not sure that if an administrator decided to remove a device while there are still active applications, we should stall his request.
Anyway, let's get this patch-set done.

> > The first 4 you already review and acked the fifth is in mlx4_ib and has no
> > comments to fix so far - some months in the list.
> 
> Personally, I'm not looking much at drivers..
> 
> Jason

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Re: [PATCH for-next V7 6/6] IB/ucma: HW Device hot-removal support

[Jason Gunthorpe]

On Thu, Aug 06, 2015 at 03:36:39PM +0000, Liran Liss wrote:
> I don't think that the order matters.

It does if you want a planned 'gental' removal to be possible..

> When you do a surprise removal, you disconnect the application from
> both ucma and uverbs device references.  In this state, the only
> thing that the application can do is close all handles.  It doesn't
> matter if you succeed closing a resource on a device that is still
> accessible, or "close" an already destroyed resource...

Hurm. That makese sense, but that isn't entirely what this patch set
does - it is rough when facing the user, but the kernel side is
actually quite gental.. Ie the RDMA CM still sends GMPs on this
shutdown path.. Looks like the various storage ULP shutdowns are
pretty gental too.

So, it is easy to get confused what the point here is..

> The primary reason for device surprise removal is to recover from
> device fatal errors or PCI errors.

Okay, this makes sense to me. Maybe some more patches will come to be
rougher to the kernel ULPs..

> For the administrative removal use case, can consider providing
> applications a grace period before disconnecting them in a future
> patch set.  Even here, however, I am not sure that if an
> administrator decided to remove a device while there are still
> active applications, we should stall his request.

Well, it can be discussed separately.

As an example, I think it is important, if you
want to hot-unplug a storage controller the admin expects a clean
storage shutdown. I think in-kernel storage drivers do that
already. IB shouldn't really be much different.

> Anyway, let's get this patch-set done.

Still needs to have the locking fixed..

Jason
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RE: [PATCH for-next V7 6/6] IB/ucma: HW Device hot-removal support

[Liran Liss]

> From: Jason Gunthorpe [mailto:jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org]
> 
> It does if you want a planned 'gental' removal to be possible..
> 

There could be a lot of design options for a 'gentle' removal, such as first sending a 'prepare' event, and only then doing the flow proposed here.
I do not want to address this now.

> > When you do a surprise removal, you disconnect the application from
> > both ucma and uverbs device references.  In this state, the only
> > thing that the application can do is close all handles.  It doesn't
> > matter if you succeed closing a resource on a device that is still
> > accessible, or "close" an already destroyed resource...
> 
> Hurm. That makese sense, but that isn't entirely what this patch set
> does - it is rough when facing the user, but the kernel side is
> actually quite gental.. Ie the RDMA CM still sends GMPs on this
> shutdown path.. Looks like the various storage ULP shutdowns are
> pretty gental too.
> 

Right.
Kernel removal is always gentle, because kernel ULPs are trusted to close within a finite time.

> As an example, I think it is important, if you
> want to hot-unplug a storage controller the admin expects a clean
> storage shutdown. I think in-kernel storage drivers do that
> already. IB shouldn't really be much different.
> 

If a storage stack has user-space components, then our future 'gentle' closing will take care of that.

> > Anyway, let's get this patch-set done.
> 
> Still needs to have the locking fixed..

As pointed out (https://www.mail-archive.com/linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org/msg27023.html), this "barrier" scheme is used in several places including in the RDMA stack.
If there is no functional issue with the code, we can discuss how to address this scheme systematically later.

--Liran
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Re: [PATCH for-next V7 6/6] IB/ucma: HW Device hot-removal support

[Jason Gunthorpe]

On Tue, Aug 11, 2015 at 12:47:03PM +0000, Liran Liss wrote:

> > Still needs to have the locking fixed..
>
> As pointed out
> (https://www.mail-archive.com/linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org/msg27023.html),
> this "barrier" scheme is used in several places including in the
> RDMA stack.  If there is no functional issue with the code, we can
> discuss how to address this scheme systematically later.

That's not an argument. closing has nonsensical locking, the ugly
empty mutex is part of that same mess.

Jason
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Re: [PATCH for-next V7 6/6] IB/ucma: HW Device hot-removal support

[Jason Gunthorpe]

On Tue, Aug 04, 2015 at 05:03:28PM +0300, Yishai Hadas wrote:
> Currently, IB/cma remove_one flow blocks until all user descriptor managed by
> IB/ucma are released. This prevents hot-removal of IB devices. This patch
> allows IB/cma to remove devices regardless of user space activity. Upon getting
> the RDMA_CM_EVENT_DEVICE_REMOVAL event we close all the underlying HW resources
> for the given ucontext. The ucontext itself is still alive till its explicit
> destroying by its creator.

Implementation aside,

This changes the policy of the ucma from
 Tell user space and expect it to synchronously clean up
To
 Tell user space we already nuked the RDMA device asynchronously

Do we even want to do that unconditionally?

Shouldn't the kernel at least give userspace some time to respond to
the event before nuking the world?

I'm now also wondering if we have some ordering issues on
removal. Will uverbs continue to work while ucma is active?

It looks like at least we can rmmod ib_uverbs and stuff goes really
sideways for poor apps. That is probably a corner case though..

Jason
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Re: [PATCH for-next V7 6/6] IB/ucma: HW Device hot-removal support

[Yishai Hadas]

On 8/5/2015 3:23 AM, Jason Gunthorpe wrote:
> On Tue, Aug 04, 2015 at 05:03:28PM +0300, Yishai Hadas wrote:
>> Currently, IB/cma remove_one flow blocks until all user descriptor managed by
>> IB/ucma are released. This prevents hot-removal of IB devices. This patch
>> allows IB/cma to remove devices regardless of user space activity. Upon getting
>> the RDMA_CM_EVENT_DEVICE_REMOVAL event we close all the underlying HW resources
>> for the given ucontext. The ucontext itself is still alive till its explicit
>> destroying by its creator.
>
> Implementation aside,
>
> This changes the policy of the ucma from
>   Tell user space and expect it to synchronously clean up
> To
>   Tell user space we already nuked the RDMA device asynchronously
>
> Do we even want to do that unconditionally?

Yes, the kernel should not depend on userspace applications to approve 
when it has some fatal error or device is removed/unbinded.

>
> Shouldn't the kernel at least give userspace some time to respond to
> the event before nuking the world?

No, the kernel activity is asynchronous to user-space, has higher 
priority and should not wait for. The kernel raises up an event 
(RDMA_CM_EVENT_DEVICE_REMOVAL) let userspace to know that the device was 
removed and continue.
Application that handles events (as expected to do ..) should get it and 
take relevant action items. Further application calls will result in an 
error but application will stay alive.

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