[PATCH] zram: avoid doing zs_malloc() with direct reclaim within mutex

[Barry Song (Xiaomi)]

Signed-off-by: Barry Song (Xiaomi) <baohua@xxxxxxxxxx>
---
 drivers/block/zram/zram_drv.c | 43 ++++++++++++++++++++++++++++-------
 1 file changed, 35 insertions(+), 8 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index cfa98846ac48..e00d896a101f 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -2218,6 +2218,35 @@ static int write_same_filled_page(struct zram *zram, unsigned long fill,
 	return 0;
 }
 
+/*
+ * try non-sleepable allocation for !async backend, then try
+ * sleepable allocation; for async backend, we always begin
+ * from sleepable allocation
+ */
+static unsigned long zram_zs_malloc(struct zram *zram, struct zcomp_strm *zstrm,
+		size_t comp_len, const int nid, void **bounce)
+{
+	unsigned long handle;
+
+	handle = zs_malloc(zram->mem_pool, comp_len,
+			__GFP_KSWAPD_RECLAIM | __GFP_NOWARN |
+			__GFP_HIGHMEM | __GFP_MOVABLE, nid);
+	if (!IS_ERR_VALUE(handle))
+		return handle;
+
+	*bounce = kmalloc(comp_len, GFP_ATOMIC);
+	if (!*bounce)
+		return (unsigned long)ERR_PTR(-ENOMEM);
+	memcpy(*bounce, zstrm->buffer, comp_len);
+
+	/* Don't hold mutex to do a sleepable allocation */
+	zcomp_stream_put(zstrm);
+	handle = zs_malloc(zram->mem_pool, comp_len,
+			GFP_NOIO | __GFP_NOWARN |
+			__GFP_HIGHMEM | __GFP_MOVABLE, nid);
+	return handle;
+}
+
 static int write_incompressible_page(struct zram *zram, struct page *page,
 				     u32 index)
 {
@@ -2264,7 +2293,7 @@ static int zram_write_page(struct zram *zram, struct page *page, u32 index)
 	int ret = 0;
 	unsigned long handle;
 	unsigned int comp_len;
-	void *mem;
+	void *mem, *bounce = NULL;
 	struct zcomp_strm *zstrm;
 	unsigned long element;
 	bool same_filled;
@@ -2292,22 +2321,20 @@ static int zram_write_page(struct zram *zram, struct page *page, u32 index)
 		return write_incompressible_page(zram, page, index);
 	}
 
-	handle = zs_malloc(zram->mem_pool, comp_len,
-			   GFP_NOIO | __GFP_NOWARN |
-			   __GFP_HIGHMEM | __GFP_MOVABLE, page_to_nid(page));
+	handle = zram_zs_malloc(zram, zstrm, comp_len, page_to_nid(page), &bounce);
 	if (IS_ERR_VALUE(handle)) {
-		zcomp_stream_put(zstrm);
+		bounce ? kfree(bounce) : zcomp_stream_put(zstrm);
 		return PTR_ERR((void *)handle);
 	}
 
 	if (!zram_can_store_page(zram)) {
-		zcomp_stream_put(zstrm);
+		bounce ? kfree(bounce) : zcomp_stream_put(zstrm);
 		zs_free(zram->mem_pool, handle);
 		return -ENOMEM;
 	}
 
-	zs_obj_write(zram->mem_pool, handle, zstrm->buffer, comp_len);
-	zcomp_stream_put(zstrm);
+	zs_obj_write(zram->mem_pool, handle, bounce ? : zstrm->buffer, comp_len);
+	bounce ? kfree(bounce) : zcomp_stream_put(zstrm);
 
 	slot_lock(zram, index);
 	slot_free(zram, index);
-- 
2.39.3 (Apple Git-146)