Fix QAT allocation failure return value

When qat_compress() fails to allocate the required contigeous memory
it mistakenly returns success.  This prevents the fallback software
compression from taking over and (un)compressing the block.

Resolve the issue by correctly setting the local 'status' variable
on all exit paths.  Furthermore, initialize it to CPA_STATUS_FAIL
to ensure qat_compress() always fails safe to guard against any
similar bugs in the future.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #9784

module/os/linux/zfs/qat_compress.c

@@ -248,7 +248,7 @@ qat_compress_impl(qat_compress_dir_t dir, char *src, int src_len,
 	Cpa8U *buffer_meta_dst = NULL;
 	Cpa32U buffer_meta_size = 0;
 	CpaDcRqResults dc_results;
-	CpaStatus status = CPA_STATUS_SUCCESS;
+	CpaStatus status = CPA_STATUS_FAIL;
 	Cpa32U hdr_sz = 0;
 	Cpa32U compressed_sz;
 	Cpa32U num_src_buf = (src_len >> PAGE_SHIFT) + 2;
@@ -277,16 +277,19 @@ qat_compress_impl(qat_compress_dir_t dir, char *src, int src_len,
 	Cpa32U dst_buffer_list_mem_size = sizeof (CpaBufferList) +
 	    ((num_dst_buf + num_add_buf) * sizeof (CpaFlatBuffer));
 
-	if (QAT_PHYS_CONTIG_ALLOC(&in_pages,
-	    num_src_buf * sizeof (struct page *)) != CPA_STATUS_SUCCESS)
+	status = QAT_PHYS_CONTIG_ALLOC(&in_pages,
+	    num_src_buf * sizeof (struct page *));
+	if (status != CPA_STATUS_SUCCESS)
 		goto fail;
 
-	if (QAT_PHYS_CONTIG_ALLOC(&out_pages,
-	    num_dst_buf * sizeof (struct page *)) != CPA_STATUS_SUCCESS)
+	status = QAT_PHYS_CONTIG_ALLOC(&out_pages,
+	    num_dst_buf * sizeof (struct page *));
+	if (status != CPA_STATUS_SUCCESS)
 		goto fail;
 
-	if (QAT_PHYS_CONTIG_ALLOC(&add_pages,
-	    num_add_buf * sizeof (struct page *)) != CPA_STATUS_SUCCESS)
+	status = QAT_PHYS_CONTIG_ALLOC(&add_pages,
+	    num_add_buf * sizeof (struct page *));
+	if (status != CPA_STATUS_SUCCESS)
 		goto fail;
 
 	i = (Cpa32U)atomic_inc_32_nv(&inst_num) % num_inst;
@@ -295,28 +298,28 @@ qat_compress_impl(qat_compress_dir_t dir, char *src, int src_len,
 
 	cpaDcBufferListGetMetaSize(dc_inst_handle, num_src_buf,
 	    &buffer_meta_size);
-	if (QAT_PHYS_CONTIG_ALLOC(&buffer_meta_src, buffer_meta_size) !=
-	    CPA_STATUS_SUCCESS)
+	status = QAT_PHYS_CONTIG_ALLOC(&buffer_meta_src, buffer_meta_size);
+	if (status != CPA_STATUS_SUCCESS)
 		goto fail;
 
 	cpaDcBufferListGetMetaSize(dc_inst_handle, num_dst_buf + num_add_buf,
 	    &buffer_meta_size);
-	if (QAT_PHYS_CONTIG_ALLOC(&buffer_meta_dst, buffer_meta_size) !=
-	    CPA_STATUS_SUCCESS)
+	status = QAT_PHYS_CONTIG_ALLOC(&buffer_meta_dst, buffer_meta_size);
+	if (status != CPA_STATUS_SUCCESS)
 		goto fail;
 
 	/* build source buffer list */
-	if (QAT_PHYS_CONTIG_ALLOC(&buf_list_src, src_buffer_list_mem_size) !=
-	    CPA_STATUS_SUCCESS)
+	status = QAT_PHYS_CONTIG_ALLOC(&buf_list_src, src_buffer_list_mem_size);
+	if (status != CPA_STATUS_SUCCESS)
 		goto fail;
 
 	flat_buf_src = (CpaFlatBuffer *)(buf_list_src + 1);
 
 	buf_list_src->pBuffers = flat_buf_src; /* always point to first one */
 
 	/* build destination buffer list */
-	if (QAT_PHYS_CONTIG_ALLOC(&buf_list_dst, dst_buffer_list_mem_size) !=
-	    CPA_STATUS_SUCCESS)
+	status = QAT_PHYS_CONTIG_ALLOC(&buf_list_dst, dst_buffer_list_mem_size);
+	if (status != CPA_STATUS_SUCCESS)
 		goto fail;
 
 	flat_buf_dst = (CpaFlatBuffer *)(buf_list_dst + 1);