Re: [PATCH v2 2/7] drm/ttm/pool: Fix ttm_pool_alloc error path

Christian König <christian.koenig@xxxxxxx> · Wed, 8 Mar 2023 09:48:43 +0100

Am 07.03.23 um 15:46 schrieb Thomas Hellström:
When hitting an error, the error path forgot to unmap dma mappings and
could call set_pages_wb() on already uncached pages.

Fix this by introducing a common __ttm_pool_free() function that
does the right thing.

v2:
- Simplify __ttm_pool_free() (Christian König)

Fixes: d099fc8f540a ("drm/ttm: new TT backend allocation pool v3")
Cc: Christian König <christian.koenig@xxxxxxx>
Cc: Dave Airlie <airlied@xxxxxxxxxx>
Cc: Christian Koenig <christian.koenig@xxxxxxx>
Cc: Huang Rui <ray.huang@xxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
---
  drivers/gpu/drm/ttm/ttm_pool.c | 68 +++++++++++++++++++---------------
  1 file changed, 38 insertions(+), 30 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
index aa116a7bbae3..0b6e20613d19 100644
--- a/drivers/gpu/drm/ttm/ttm_pool.c
+++ b/drivers/gpu/drm/ttm/ttm_pool.c
@@ -367,6 +367,30 @@ static int ttm_pool_page_allocated(struct ttm_pool *pool, unsigned int order,
  	return 0;
  }
  
+static void __ttm_pool_free(struct ttm_pool *pool, struct ttm_tt *tt,

Maybe name that ttm_pool_free_range() and add a comment why we need it. 
Something like "/* Cleanup all pages in the tt between start_page till 
end_page */".

Apart from that looks good to me.

Regards,
Christian.

+			    enum ttm_caching caching,
+			    pgoff_t start_page, pgoff_t end_page)
+{
+	struct page **pages = tt->pages;
+	unsigned int order;
+	pgoff_t i, nr;
+
+	for (i = start_page; i < end_page; i += nr, pages += nr) {
+		struct ttm_pool_type *pt = NULL;
+
+		order = ttm_pool_page_order(pool, *pages);
+		nr = (1UL << order);
+		if (tt->dma_address)
+			ttm_pool_unmap(pool, tt->dma_address[i], nr);
+
+		pt = ttm_pool_select_type(pool, caching, order);
+		if (pt)
+			ttm_pool_type_give(pt, *pages);
+		else
+			ttm_pool_free_page(pool, caching, order, *pages);
+	}
+}
+
  /**
   * ttm_pool_alloc - Fill a ttm_tt object
   *
@@ -382,12 +406,14 @@ static int ttm_pool_page_allocated(struct ttm_pool *pool, unsigned int order,
  int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
  		   struct ttm_operation_ctx *ctx)
  {
-	unsigned long num_pages = tt->num_pages;
+	pgoff_t num_pages = tt->num_pages;
  	dma_addr_t *dma_addr = tt->dma_address;
  	struct page **caching = tt->pages;
  	struct page **pages = tt->pages;
+	enum ttm_caching page_caching;
  	gfp_t gfp_flags = GFP_USER;
-	unsigned int i, order;
+	pgoff_t caching_divide;
+	unsigned int order;
  	struct page *p;
  	int r;
  
@@ -410,6 +436,7 @@ int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
  	     order = min_t(unsigned int, order, __fls(num_pages))) {
  		struct ttm_pool_type *pt;
  
+		page_caching = tt->caching;
  		pt = ttm_pool_select_type(pool, tt->caching, order);
  		p = pt ? ttm_pool_type_take(pt) : NULL;
  		if (p) {
@@ -418,6 +445,7 @@ int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
  			if (r)
  				goto error_free_page;
  
+			caching = pages;
  			do {
  				r = ttm_pool_page_allocated(pool, order, p,
  							    &dma_addr,
@@ -426,14 +454,15 @@ int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
  				if (r)
  					goto error_free_page;
  
+				caching = pages;
  				if (num_pages < (1 << order))
  					break;
  
  				p = ttm_pool_type_take(pt);
  			} while (p);
-			caching = pages;
  		}
  
+		page_caching = ttm_cached;
  		while (num_pages >= (1 << order) &&
  		       (p = ttm_pool_alloc_page(pool, gfp_flags, order))) {
  
@@ -442,6 +471,7 @@ int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
  							   tt->caching);
  				if (r)
  					goto error_free_page;
+				caching = pages;
  			}
  			r = ttm_pool_page_allocated(pool, order, p, &dma_addr,
  						    &num_pages, &pages);
@@ -468,15 +498,13 @@ int ttm_pool_alloc(struct ttm_pool *pool, struct ttm_tt *tt,
  	return 0;
  
  error_free_page:
-	ttm_pool_free_page(pool, tt->caching, order, p);
+	ttm_pool_free_page(pool, page_caching, order, p);
  
  error_free_all:
  	num_pages = tt->num_pages - num_pages;
-	for (i = 0; i < num_pages; ) {
-		order = ttm_pool_page_order(pool, tt->pages[i]);
-		ttm_pool_free_page(pool, tt->caching, order, tt->pages[i]);
-		i += 1 << order;
-	}
+	caching_divide = caching - tt->pages;
+	__ttm_pool_free(pool, tt, tt->caching, 0, caching_divide);
+	__ttm_pool_free(pool, tt, ttm_cached, caching_divide, num_pages);
  
  	return r;
  }
@@ -492,27 +520,7 @@ EXPORT_SYMBOL(ttm_pool_alloc);
   */
  void ttm_pool_free(struct ttm_pool *pool, struct ttm_tt *tt)
  {
-	unsigned int i;
-
-	for (i = 0; i < tt->num_pages; ) {
-		struct page *p = tt->pages[i];
-		unsigned int order, num_pages;
-		struct ttm_pool_type *pt;
-
-		order = ttm_pool_page_order(pool, p);
-		num_pages = 1ULL << order;
-		if (tt->dma_address)
-			ttm_pool_unmap(pool, tt->dma_address[i], num_pages);
-
-		pt = ttm_pool_select_type(pool, tt->caching, order);
-		if (pt)
-			ttm_pool_type_give(pt, tt->pages[i]);
-		else
-			ttm_pool_free_page(pool, tt->caching, order,
-					   tt->pages[i]);
-
-		i += num_pages;
-	}
+	__ttm_pool_free(pool, tt, tt->caching, 0, tt->num_pages);
  
  	while (atomic_long_read(&allocated_pages) > page_pool_size)
  		ttm_pool_shrink();







