From 31c70f97bec3107805df0f491485e7eacbc3a3ae Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Tue, 12 Dec 2017 18:06:52 +0000
Subject: [PATCH] drm/i915: Ratelimit request allocation under oom
Git-commit: 31c70f97bec3107805df0f491485e7eacbc3a3ae
Patch-mainline: v4.16-rc1
References: FATE#322643 bsc#1055900

If we fail to allocate a request, we can reap the outstanding requests
and push them to the request's slab's freelist before trying again. This
forces us to ratelimit malicious clients that tie up all of the system
resources in requests, instead of causing a system-wide oom.

Testcase: igt/gem_shrink/execbuf1
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171212180652.22061-3-chris@chris-wilson.co.uk
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/i915_gem_request.c |   19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -677,10 +677,21 @@ i915_gem_request_alloc(struct intel_engi
 	 *
 	 * Do not use kmem_cache_zalloc() here!
 	 */
-	req = kmem_cache_alloc(dev_priv->requests, GFP_KERNEL);
-	if (!req) {
-		ret = -ENOMEM;
-		goto err_unreserve;
+	req = kmem_cache_alloc(dev_priv->requests,
+			       GFP_KERNEL | __GFP_REPEAT | __GFP_NOWARN);
+	if (unlikely(!req)) {
+		/* Ratelimit ourselves to prevent oom from malicious clients */
+		ret = i915_gem_wait_for_idle(dev_priv,
+					     I915_WAIT_LOCKED |
+					     I915_WAIT_INTERRUPTIBLE);
+		if (ret)
+			goto err_unreserve;
+
+		req = kmem_cache_alloc(dev_priv->requests, GFP_KERNEL);
+		if (!req) {
+			ret = -ENOMEM;
+			goto err_unreserve;
+		}
 	}
 
 	req->timeline = i915_gem_context_lookup_timeline(ctx, engine);