drm/i915: Make GEM contexts track DRM clients

Make GEM contexts keep a reference to i915_drm_client for the whole of
of their lifetime which will come handy in following patches.

v2: Don't bother supporting selftests contexts from debugfs. (Chris)
v3 (Lucas): Finish constructing ctx before adding it to the list
v4 (Ram): Rebase.
v5: Trivial rebase for proto ctx changes.
v6: Rebase after clients no longer track name and pid.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> # v5
Reviewed-by: Aravind Iddamsetty <aravind.iddamsetty@intel.com> # v5
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220401142205.3123159-3-tvrtko.ursulin@linux.intel.com

drivers/gpu/drm/i915/gem/i915_gem_context.c

@@ -1256,6 +1256,9 @@ static void i915_gem_context_release_work(struct work_struct *work)
 	if (ctx->pxp_wakeref)
 		intel_runtime_pm_put(&ctx->i915->runtime_pm, ctx->pxp_wakeref);
 
+	if (ctx->client)
+		i915_drm_client_put(ctx->client);
+
 	mutex_destroy(&ctx->engines_mutex);
 	mutex_destroy(&ctx->lut_mutex);
 
@@ -1662,6 +1665,8 @@ static void gem_context_register(struct i915_gem_context *ctx,
 	ctx->file_priv = fpriv;
 
 	ctx->pid = get_task_pid(current, PIDTYPE_PID);
+	ctx->client = i915_drm_client_get(fpriv->client);
+
 	snprintf(ctx->name, sizeof(ctx->name), "%s[%d]",
 		 current->comm, pid_nr(ctx->pid));
 

drivers/gpu/drm/i915/gem/i915_gem_context_types.h

@@ -293,6 +293,9 @@ struct i915_gem_context {
 	/** @link: place with &drm_i915_private.context_list */
 	struct list_head link;
 
+	/** @client: struct i915_drm_client */
+	struct i915_drm_client *client;
+
 	/**
 	 * @ref: reference count
 	 *