[PATCH 08/25] IB/uverbs: ufile must be freed only when not used anymore

[Shamir Rabinovitch <srabinov7@gmail.com>]

From: Shamir Rabinovitch <shamir.rabinovitch@oracle.com>

ufile (&ucontext) with the process who own them must not be released
when there are other ufile (&ucontext) that depens at them.

Signed-off-by: Shamir Rabinovitch <shamir.rabinovitch@oracle.com>
Signed-off-by: Shamir Rabinovitch <srabinov7@gmail.com>
---
 drivers/infiniband/core/rdma_core.c   | 29 +++++++++++++++++++++++++++
 drivers/infiniband/core/uverbs.h      | 22 ++++++++++++++++++++
 drivers/infiniband/core/uverbs_cmd.c  | 16 +++++++++++++++
 drivers/infiniband/core/uverbs_main.c |  4 ++++
 4 files changed, 71 insertions(+)

diff --git a/drivers/infiniband/core/rdma_core.c b/drivers/infiniband/core/rdma_core.c
index 651625f632d7..c81ff8e28fc6 100644
--- a/drivers/infiniband/core/rdma_core.c
+++ b/drivers/infiniband/core/rdma_core.c
@@ -841,6 +841,33 @@ static void ufile_destroy_ucontext(struct ib_uverbs_file *ufile,
 	ufile->ucontext = NULL;
 }
 
+static void __uverbs_ufile_refcount(struct ib_uverbs_file *ufile)
+{
+	int wait;
+
+	if (ufile->parent) {
+		pr_debug("%s: release parent ufile. ufile %p parent %p\n",
+			 __func__, ufile, ufile->parent);
+		if (atomic_dec_and_test(&ufile->parent->refcount))
+			complete(&ufile->parent->context_released);
+	}
+
+	if (!atomic_dec_and_test(&ufile->refcount)) {
+wait:
+		wait = wait_for_completion_interruptible_timeout(
+			&ufile->context_released, 3*HZ);
+		if (wait == -ERESTARTSYS) {
+			WARN_ONCE(1,
+			"signal while waiting for context release! ufile %p\n",
+				ufile);
+		} else if (wait == 0) {
+			pr_debug("%s: timeout while waiting for context release! ufile %p\n",
+				 __func__, ufile);
+			goto wait;
+		}
+	}
+}
+
 static int __uverbs_cleanup_ufile(struct ib_uverbs_file *ufile,
 				  enum rdma_remove_reason reason)
 {
@@ -923,6 +950,8 @@ void uverbs_destroy_ufile_hw(struct ib_uverbs_file *ufile,
 	if (!list_empty(&ufile->uobjects))
 		__uverbs_cleanup_ufile(ufile, reason);
 
+	__uverbs_ufile_refcount(ufile);
+
 	ufile_destroy_ucontext(ufile, reason);
 
 done:
diff --git a/drivers/infiniband/core/uverbs.h b/drivers/infiniband/core/uverbs.h
index cf76336cb460..c7e711188567 100644
--- a/drivers/infiniband/core/uverbs.h
+++ b/drivers/infiniband/core/uverbs.h
@@ -165,6 +165,28 @@ struct ib_uverbs_file {
 	struct xarray		idr;
 
 	struct file	       *filp;
+
+	/* context sharing support */
+
+	/*
+	 * refcount=1 : zero external context depend on this context
+	 * refcount>1 : (refcount-1) external context depend on this context
+	 */
+	atomic_t		refcount;
+
+	/*
+	 * parent =NULL : this context has not imported any objects
+	 * parent!=NULL : this context imported objects from parent context
+	 */
+	struct ib_uverbs_file  *parent;
+
+	/*
+	 * context_released completion is signalled by the last
+	 * user of this context in case of shared context.
+	 * any pre matured release of the context will be delayed
+	 * till the last user of this context is gone.
+	 */
+	struct completion	context_released;
 };
 
 struct ib_uverbs_event {
diff --git a/drivers/infiniband/core/uverbs_cmd.c b/drivers/infiniband/core/uverbs_cmd.c
index 21f0a1a986f4..8d015587946b 100644
--- a/drivers/infiniband/core/uverbs_cmd.c
+++ b/drivers/infiniband/core/uverbs_cmd.c
@@ -3816,6 +3816,10 @@ static int ib_uverbs_import_lock(struct uverbs_attr_bundle *attrs,
 	struct ib_uverbs_device *fd_dev;
 	int ret = 0;
 
+	/* shared context cannot import */
+	if (atomic_read(&file->refcount) > 1)
+		return -EINVAL;
+
 	*filep = fget(fd);
 	if (!*filep)
 		return -EINVAL;
@@ -3829,6 +3833,18 @@ static int ib_uverbs_import_lock(struct uverbs_attr_bundle *attrs,
 	*ufile = (*filep)->private_data;
 	fd_dev = (*ufile)->device;
 
+	if (file->parent) {
+		/* multiple import must use same parent context! */
+		if (file->parent != *ufile) {
+			ret = -EINVAL;
+			goto file;
+		}
+	} else {
+		/* first import must update parent refcount */
+		file->parent = *ufile;
+		atomic_inc(&(*ufile)->refcount);
+	}
+
 	/* check that both files belong to same ib_device */
 	if (dev != fd_dev) {
 		ret = -EINVAL;
diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
index fa88a586284c..3c28034a7a9a 100644
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -1081,6 +1081,10 @@ static int ib_uverbs_open(struct inode *inode, struct file *filp)
 		goto err;
 	}
 
+	/* shared context support */
+	atomic_set(&file->refcount, 1);
+	init_completion(&file->context_released);
+
 	file->device	 = dev;
 	kref_init(&file->ref);
 	mutex_init(&file->ucontext_lock);
-- 
2.20.1