IB/core: Implement support for MMU notifiers regarding on demand paging regions

* Add an interval tree implementation for ODP umems. Create an
  interval tree for each ucontext (including a count of the number of
  ODP MRs in this context, semaphore, etc.), and register ODP umems in
  the interval tree.
* Add MMU notifiers handling functions, using the interval tree to
  notify only the relevant umems and underlying MRs.
* Register to receive MMU notifier events from the MM subsystem upon
  ODP MR registration (and unregister accordingly).
* Add a completion object to synchronize the destruction of ODP umems.
* Add mechanism to abort page faults when there's a concurrent invalidation.

The way we synchronize between concurrent invalidations and page
faults is by keeping a counter of currently running invalidations, and
a sequence number that is incremented whenever an invalidation is
caught. The page fault code checks the counter and also verifies that
the sequence number hasn't progressed before it updates the umem's
page tables. This is similar to what the kvm module does.

In order to prevent the case where we register a umem in the middle of
an ongoing notifier, we also keep a per ucontext counter of the total
number of active mmu notifiers. We only enable new umems when all the
running notifiers complete.

Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Shachar Raindel <raindel@mellanox.com>
Signed-off-by: Haggai Eran <haggaie@mellanox.com>
Signed-off-by: Yuval Dagan <yuvalda@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index 3af5dcad1b69..0d74f1de99aa 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -51,6 +51,7 @@
 #include <uapi/linux/if_ether.h>
 
 #include <linux/atomic.h>
+#include <linux/mmu_notifier.h>
 #include <asm/uaccess.h>
 
 extern struct workqueue_struct *ib_wq;
@@ -1139,6 +1140,8 @@ struct ib_fmr_attr {
 	u8	page_shift;
 };
 
+struct ib_umem;
+
 struct ib_ucontext {
 	struct ib_device       *device;
 	struct list_head	pd_list;
@@ -1153,6 +1156,22 @@ struct ib_ucontext {
 	int			closing;
 
 	struct pid             *tgid;
+#ifdef CONFIG_INFINIBAND_ON_DEMAND_PAGING
+	struct rb_root      umem_tree;
+	/*
+	 * Protects .umem_rbroot and tree, as well as odp_mrs_count and
+	 * mmu notifiers registration.
+	 */
+	struct rw_semaphore	umem_rwsem;
+	void (*invalidate_range)(struct ib_umem *umem,
+				 unsigned long start, unsigned long end);
+
+	struct mmu_notifier	mn;
+	atomic_t		notifier_count;
+	/* A list of umems that don't have private mmu notifier counters yet. */
+	struct list_head	no_private_counters;
+	int                     odp_mrs_count;
+#endif
 };
 
 struct ib_uobject {