[PATCH 21/34] drm/i915: Convert get_page to XArray

From: Matthew Wilcox <willy@infradead.org>
To: dri-devel@lists.freedesktop.org
Cc: Matthew Wilcox <willy@infradead.org>
Subject: [PATCH 21/34] drm/i915: Convert get_page to XArray
Date: Thu, 21 Feb 2019 10:42:01 -0800	[thread overview]
Message-ID: <20190221184226.2149-42-willy@infradead.org> (raw)
In-Reply-To: <20190221184226.2149-1-willy@infradead.org>

This initially seemed like an ideal use-case for the store_range
functionality, but there's no easy way to determine where we were
relative to the base of the entry.  So this is a straightforward
conversion which doesn't even touch the locking.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
---
 drivers/gpu/drm/i915/i915_gem.c         | 38 ++++++++++---------------
 drivers/gpu/drm/i915/i915_gem_context.h |  2 +-
 drivers/gpu/drm/i915/i915_gem_object.h  |  4 +--
 3 files changed, 18 insertions(+), 26 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 0cdccc886587..f8c36c2d32c2 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2428,13 +2428,7 @@ i915_gem_object_put_pages_gtt(struct drm_i915_gem_object *obj,
 
 static void __i915_gem_object_reset_page_iter(struct drm_i915_gem_object *obj)
 {
-	struct radix_tree_iter iter;
-	void __rcu **slot;
-
-	rcu_read_lock();
-	radix_tree_for_each_slot(slot, &obj->mm.get_page.radix, &iter, 0)
-		radix_tree_delete(&obj->mm.get_page.radix, iter.index);
-	rcu_read_unlock();
+	xa_destroy(&obj->mm.get_page.xa);
 }
 
 static struct sg_table *
@@ -4716,7 +4710,7 @@ void i915_gem_object_init(struct drm_i915_gem_object *obj,
 	init_request_active(&obj->frontbuffer_write, frontbuffer_retire);
 
 	obj->mm.madv = I915_MADV_WILLNEED;
-	INIT_RADIX_TREE(&obj->mm.get_page.radix, GFP_KERNEL | __GFP_NOWARN);
+	xa_init(&obj->mm.get_page.xa);
 	mutex_init(&obj->mm.get_page.lock);
 
 	i915_gem_info_add_obj(to_i915(obj->base.dev), obj->base.size);
@@ -6073,8 +6067,8 @@ i915_gem_object_get_sg(struct drm_i915_gem_object *obj,
 	GEM_BUG_ON(n >= obj->base.size >> PAGE_SHIFT);
 	GEM_BUG_ON(!i915_gem_object_has_pinned_pages(obj));
 
-	/* As we iterate forward through the sg, we record each entry in a
-	 * radixtree for quick repeated (backwards) lookups. If we have seen
+	/* As we iterate forward through the sg, we record each entry in an
+	 * xarray for quick repeated (backwards) lookups. If we have seen
 	 * this index previously, we will have an entry for it.
 	 *
 	 * Initial lookup is O(N), but this is amortized to O(1) for
@@ -6089,7 +6083,7 @@ i915_gem_object_get_sg(struct drm_i915_gem_object *obj,
 
 	/* We prefer to reuse the last sg so that repeated lookup of this
 	 * (or the subsequent) sg are fast - comparing against the last
-	 * sg is faster than going through the radixtree.
+	 * sg is faster than going through the xarray.
 	 */
 
 	sg = iter->sg_pos;
@@ -6099,24 +6093,22 @@ i915_gem_object_get_sg(struct drm_i915_gem_object *obj,
 	while (idx + count <= n) {
 		void *entry;
 		unsigned long i;
-		int ret;
 
 		/* If we cannot allocate and insert this entry, or the
 		 * individual pages from this range, cancel updating the
 		 * sg_idx so that on this lookup we are forced to linearly
 		 * scan onwards, but on future lookups we will try the
-		 * insertion again (in which case we need to be careful of
-		 * the error return reporting that we have already inserted
-		 * this index).
+		 * insertion again.
 		 */
-		ret = radix_tree_insert(&iter->radix, idx, sg);
-		if (ret && ret != -EEXIST)
+		if (xa_store(&iter->xa, idx, sg, GFP_KERNEL | __GFP_NOWARN)
+				== XA_ERROR(-ENOMEM))
 			goto scan;
 
 		entry = xa_mk_value(idx);
 		for (i = 1; i < count; i++) {
-			ret = radix_tree_insert(&iter->radix, idx + i, entry);
-			if (ret && ret != -EEXIST)
+			if (xa_store(&iter->xa, idx + i, entry,
+					GFP_KERNEL | __GFP_NOWARN)
+						== XA_ERROR(-ENOMEM))
 				goto scan;
 		}
 
@@ -6134,7 +6126,7 @@ i915_gem_object_get_sg(struct drm_i915_gem_object *obj,
 	if (unlikely(n < idx)) /* insertion completed by another thread */
 		goto lookup;
 
-	/* In case we failed to insert the entry into the radixtree, we need
+	/* In case we failed to insert the entry into the xarray, we need
 	 * to look beyond the current sg.
 	 */
 	while (idx + count <= n) {
@@ -6149,11 +6141,11 @@ i915_gem_object_get_sg(struct drm_i915_gem_object *obj,
 lookup:
 	rcu_read_lock();
 
-	sg = radix_tree_lookup(&iter->radix, n);
+	sg = xa_load(&iter->xa, n);
 	GEM_BUG_ON(!sg);
 
 	/* If this index is in the middle of multi-page sg entry,
-	 * the radix tree will contain a value entry that points
+	 * the xarray will contain a value entry that points
 	 * to the start of that range. We will return the pointer to
 	 * the base page and the offset of this page within the
 	 * sg entry's range.
@@ -6162,7 +6154,7 @@ i915_gem_object_get_sg(struct drm_i915_gem_object *obj,
 	if (unlikely(xa_is_value(sg))) {
 		unsigned long base = xa_to_value(sg);
 
-		sg = radix_tree_lookup(&iter->radix, base);
+		sg = xa_load(&iter->xa, base);
 		GEM_BUG_ON(!sg);
 
 		*offset = n - base;
diff --git a/drivers/gpu/drm/i915/i915_gem_context.h b/drivers/gpu/drm/i915/i915_gem_context.h
index ec22de370a22..052ad66a5bae 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.h
+++ b/drivers/gpu/drm/i915/i915_gem_context.h
@@ -27,7 +27,7 @@
 
 #include <linux/bitops.h>
 #include <linux/list.h>
-#include <linux/radix-tree.h>
+#include <linux/xarray.h>
 
 #include "i915_gem.h"
 #include "i915_scheduler.h"
diff --git a/drivers/gpu/drm/i915/i915_gem_object.h b/drivers/gpu/drm/i915/i915_gem_object.h
index 7f6493229f50..9febe70b4da9 100644
--- a/drivers/gpu/drm/i915/i915_gem_object.h
+++ b/drivers/gpu/drm/i915/i915_gem_object.h
@@ -40,7 +40,7 @@ struct drm_i915_gem_object;
 
 /*
  * struct i915_lut_handle tracks the fast lookups from handle to vma used
- * for execbuf. Although we use a radixtree for that mapping, in order to
+ * for execbuf. Although we use an xarray for that mapping, in order to
  * remove them as the object or context is closed, we need a secondary list
  * and a translation entry (i915_lut_handle).
  */
@@ -218,7 +218,7 @@ struct drm_i915_gem_object {
 			struct scatterlist *sg_pos;
 			unsigned int sg_idx; /* in pages, but 32bit eek! */
 
-			struct radix_tree_root radix;
+			struct xarray xa;
 			struct mutex lock; /* protects this cache */
 		} get_page;
 
-- 
2.20.1

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