IB/uverbs: Do not pass struct ib_device to the write based methods

This is a step to get rid of the global check for disassociation. In this
model, the ib_dev is not proven to be valid by the core code and cannot be
provided to the method. Instead, every method decides if it is able to
run after disassociation and obtains the ib_dev using one of three
different approaches:

- Call srcu_dereference on the udevice's ib_dev. As before, this means
  the method cannot be called after disassociation begins.
  (eg alloc ucontext)
- Retrieve the ib_dev from the ucontext, via ib_uverbs_get_ucontext()
- Retrieve the ib_dev from the uobject->object after checking
  under SRCU if disassociation has started (eg uobj_get)

Largely, the code is all ready for this, the main work is to provide a
ib_dev after calling uobj_alloc(). The few other places simply use
ib_uverbs_get_ucontext() to get the ib_dev.

This flexibility will let the next patches allow destroy to operate
after disassociation.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/uverbs.h

@@ -299,7 +299,6 @@ extern const struct uverbs_object_def UVERBS_OBJECT(UVERBS_OBJECT_COUNTERS);
 
 #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)
 
@@ -341,7 +340,6 @@ 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)