--- zzzz-none-000/linux-3.10.107/fs/btrfs/lzo.c	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/fs/btrfs/lzo.c	2021-02-04 17:41:59.000000000 +0000
@@ -31,8 +31,8 @@
 
 struct workspace {
 	void *mem;
-	void *buf;	/* where compressed data goes */
-	void *cbuf;	/* where decompressed data goes */
+	void *buf;	/* where decompressed data goes */
+	void *cbuf;	/* where compressed data goes */
 	struct list_head list;
 };
 
@@ -141,9 +141,9 @@
 		ret = lzo1x_1_compress(data_in, in_len, workspace->cbuf,
 				       &out_len, workspace->mem);
 		if (ret != LZO_E_OK) {
-			printk(KERN_DEBUG "btrfs deflate in loop returned %d\n",
+			printk(KERN_DEBUG "BTRFS: deflate in loop returned %d\n",
 			       ret);
-			ret = -1;
+			ret = -EIO;
 			goto out;
 		}
 
@@ -189,7 +189,7 @@
 				kunmap(out_page);
 				if (nr_pages == nr_dest_pages) {
 					out_page = NULL;
-					ret = -1;
+					ret = -E2BIG;
 					goto out;
 				}
 
@@ -207,8 +207,10 @@
 		}
 
 		/* we're making it bigger, give up */
-		if (tot_in > 8192 && tot_in < tot_out)
+		if (tot_in > 8192 && tot_in < tot_out) {
+			ret = -E2BIG;
 			goto out;
+		}
 
 		/* we're all done */
 		if (tot_in >= len)
@@ -264,8 +266,7 @@
 	char *data_in;
 	unsigned long page_in_index = 0;
 	unsigned long page_out_index = 0;
-	unsigned long total_pages_in = (srclen + PAGE_CACHE_SIZE - 1) /
-					PAGE_CACHE_SIZE;
+	unsigned long total_pages_in = DIV_ROUND_UP(srclen, PAGE_CACHE_SIZE);
 	unsigned long buf_start;
 	unsigned long buf_offset = 0;
 	unsigned long bytes;
@@ -333,7 +334,7 @@
 					break;
 
 				if (page_in_index + 1 >= total_pages_in) {
-					ret = -1;
+					ret = -EIO;
 					goto done;
 				}
 
@@ -355,8 +356,8 @@
 		if (need_unmap)
 			kunmap(pages_in[page_in_index - 1]);
 		if (ret != LZO_E_OK) {
-			printk(KERN_WARNING "btrfs decompress failed\n");
-			ret = -1;
+			printk(KERN_WARNING "BTRFS: decompress failed\n");
+			ret = -EIO;
 			break;
 		}
 
@@ -372,6 +373,8 @@
 	}
 done:
 	kunmap(pages_in[page_in_index]);
+	if (!ret)
+		btrfs_clear_biovec_end(bvec, vcnt, page_out_index, pg_offset);
 	return ret;
 }
 
@@ -399,26 +402,39 @@
 	out_len = PAGE_CACHE_SIZE;
 	ret = lzo1x_decompress_safe(data_in, in_len, workspace->buf, &out_len);
 	if (ret != LZO_E_OK) {
-		printk(KERN_WARNING "btrfs decompress failed!\n");
-		ret = -1;
+		printk(KERN_WARNING "BTRFS: decompress failed!\n");
+		ret = -EIO;
 		goto out;
 	}
 
 	if (out_len < start_byte) {
-		ret = -1;
+		ret = -EIO;
 		goto out;
 	}
 
+	/*
+	 * the caller is already checking against PAGE_SIZE, but lets
+	 * move this check closer to the memcpy/memset
+	 */
+	destlen = min_t(unsigned long, destlen, PAGE_SIZE);
 	bytes = min_t(unsigned long, destlen, out_len - start_byte);
 
 	kaddr = kmap_atomic(dest_page);
 	memcpy(kaddr, workspace->buf + start_byte, bytes);
+
+	/*
+	 * btrfs_getblock is doing a zero on the tail of the page too,
+	 * but this will cover anything missing from the decompressed
+	 * data.
+	 */
+	if (bytes < destlen)
+		memset(kaddr+bytes, 0, destlen-bytes);
 	kunmap_atomic(kaddr);
 out:
 	return ret;
 }
 
-struct btrfs_compress_op btrfs_lzo_compress = {
+const struct btrfs_compress_op btrfs_lzo_compress = {
 	.alloc_workspace	= lzo_alloc_workspace,
 	.free_workspace		= lzo_free_workspace,
 	.compress_pages		= lzo_compress_pages,