RDMA/core: Create mmap database and cookie helper functions

Create some common API's for adding entries to a xa_mmap. Searching for
an entry and freeing one.

The general approach is copied from the EFA driver and improved to be more
general and do more to help the drivers. Integration with the core allows
a reference counted scheme with a free function so that the driver can
know when its mmaps are all gone.

This significant new functionality will be helpful for drivers to have the
correct lifetime model for mmap objects.

Link: https://lore.kernel.org/r/20191030094417.16866-3-michal.kalderon@marvell.com
Signed-off-by: Ariel Elior <ariel.elior@marvell.com>
Signed-off-by: Michal Kalderon <michal.kalderon@marvell.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index 0626b62ed107..8865ec28180a 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -1473,6 +1473,7 @@ struct ib_ucontext {
 	 * Implementation details of the RDMA core, don't use in drivers:
 	 */
 	struct rdma_restrack_entry res;
+	struct xarray mmap_xa;
 };
 
 struct ib_uobject {
@@ -2258,6 +2259,21 @@ struct iw_cm_conn_param;
 
 #define DECLARE_RDMA_OBJ_SIZE(ib_struct) size_t size_##ib_struct
 
+struct rdma_user_mmap_entry {
+	struct kref ref;
+	struct ib_ucontext *ucontext;
+	unsigned long start_pgoff;
+	size_t npages;
+	bool driver_removed;
+};
+
+/* Return the offset (in bytes) the user should pass to libc's mmap() */
+static inline u64
+rdma_user_mmap_get_offset(const struct rdma_user_mmap_entry *entry)
+{
+	return (u64)entry->start_pgoff << PAGE_SHIFT;
+}
+
 /**
  * struct ib_device_ops - InfiniBand device operations
  * This structure defines all the InfiniBand device operations, providers will
@@ -2370,6 +2386,13 @@ struct ib_device_ops {
 			      struct ib_udata *udata);
 	void (*dealloc_ucontext)(struct ib_ucontext *context);
 	int (*mmap)(struct ib_ucontext *context, struct vm_area_struct *vma);
+	/**
+	 * This will be called once refcount of an entry in mmap_xa reaches
+	 * zero. The type of the memory that was mapped may differ between
+	 * entries and is opaque to the rdma_user_mmap interface.
+	 * Therefore needs to be implemented by the driver in mmap_free.
+	 */
+	void (*mmap_free)(struct rdma_user_mmap_entry *entry);
 	void (*disassociate_ucontext)(struct ib_ucontext *ibcontext);
 	int (*alloc_pd)(struct ib_pd *pd, struct ib_udata *udata);
 	void (*dealloc_pd)(struct ib_pd *pd, struct ib_udata *udata);
@@ -2815,6 +2838,18 @@ static inline int rdma_user_mmap_io(struct ib_ucontext *ucontext,
 	return -EINVAL;
 }
 #endif
+int rdma_user_mmap_entry_insert(struct ib_ucontext *ucontext,
+				struct rdma_user_mmap_entry *entry,
+				size_t length);
+struct rdma_user_mmap_entry *
+rdma_user_mmap_entry_get_pgoff(struct ib_ucontext *ucontext,
+			       unsigned long pgoff);
+struct rdma_user_mmap_entry *
+rdma_user_mmap_entry_get(struct ib_ucontext *ucontext,
+			 struct vm_area_struct *vma);
+void rdma_user_mmap_entry_put(struct rdma_user_mmap_entry *entry);
+
+void rdma_user_mmap_entry_remove(struct rdma_user_mmap_entry *entry);
 
 static inline int ib_copy_from_udata(void *dest, struct ib_udata *udata, size_t len)
 {