test_kho: unpreserve memory in case of error

If there is an error half way through KHO memory preservation, we should
rollback and unpreserve everything that is partially preserved.

Link: https://lkml.kernel.org/r/20251101142325.1326536-6-pasha.tatashin@soleen.com
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Changyuan Lyu <changyuanl@google.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Pratyush Yadav <pratyush@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Simon Horman <horms@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Zhu Yanjun <yanjun.zhu@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/test_kho.c

@@ -33,17 +33,28 @@ struct kho_test_state {
 	unsigned int nr_folios;
 	struct folio **folios;
 	phys_addr_t *folios_info;
+	struct kho_vmalloc folios_info_phys;
+	int nr_folios_preserved;
 	struct folio *fdt;
 	__wsum csum;
 };
 
 static struct kho_test_state kho_test_state;
 
-static int kho_test_save_data(struct kho_test_state *state, void *fdt)
+static void kho_test_unpreserve_data(struct kho_test_state *state)
+{
+	for (int i = 0; i < state->nr_folios_preserved; i++)
+		kho_unpreserve_folio(state->folios[i]);
+
+	kho_unpreserve_vmalloc(&state->folios_info_phys);
+	vfree(state->folios_info);
+}
+
+static int kho_test_preserve_data(struct kho_test_state *state)
 {
-	phys_addr_t *folios_info __free(kvfree) = NULL;
 	struct kho_vmalloc folios_info_phys;
-	int err = 0;
+	phys_addr_t *folios_info;
+	int err;
 
 	folios_info = vmalloc_array(state->nr_folios, sizeof(*folios_info));
 	if (!folios_info)
@@ -51,64 +62,98 @@ static int kho_test_save_data(struct kho_test_state *state, void *fdt)
 
 	err = kho_preserve_vmalloc(folios_info, &folios_info_phys);
 	if (err)
-		return err;
+		goto err_free_info;
+
+	state->folios_info_phys = folios_info_phys;
+	state->folios_info = folios_info;
 
 	for (int i = 0; i < state->nr_folios; i++) {
 		struct folio *folio = state->folios[i];
 		unsigned int order = folio_order(folio);
 
 		folios_info[i] = virt_to_phys(folio_address(folio)) | order;
-
 		err = kho_preserve_folio(folio);
 		if (err)
-			break;
+			goto err_unpreserve;
+		state->nr_folios_preserved++;
 	}
 
+	return 0;
+
+err_unpreserve:
+	/*
+	 * kho_test_unpreserve_data frees folio_info, bail out immediately to
+	 * avoid double free
+	 */
+	kho_test_unpreserve_data(state);
+	return err;
+
+err_free_info:
+	vfree(folios_info);
+	return err;
+}
+
+static int kho_test_prepare_fdt(struct kho_test_state *state, ssize_t fdt_size)
+{
+	const char compatible[] = KHO_TEST_COMPAT;
+	unsigned int magic = KHO_TEST_MAGIC;
+	void *fdt = folio_address(state->fdt);
+	int err;
+
+	err = fdt_create(fdt, fdt_size);
+	err |= fdt_finish_reservemap(fdt);
+	err |= fdt_begin_node(fdt, "");
+	err |= fdt_property(fdt, "compatible", compatible, sizeof(compatible));
+	err |= fdt_property(fdt, "magic", &magic, sizeof(magic));
+
 	err |= fdt_begin_node(fdt, "data");
 	err |= fdt_property(fdt, "nr_folios", &state->nr_folios,
 			    sizeof(state->nr_folios));
-	err |= fdt_property(fdt, "folios_info", &folios_info_phys,
-			    sizeof(folios_info_phys));
+	err |= fdt_property(fdt, "folios_info", &state->folios_info_phys,
+			    sizeof(state->folios_info_phys));
 	err |= fdt_property(fdt, "csum", &state->csum, sizeof(state->csum));
 	err |= fdt_end_node(fdt);
 
-	if (!err)
-		state->folios_info = no_free_ptr(folios_info);
+	err |= fdt_end_node(fdt);
+	err |= fdt_finish(fdt);
 
 	return err;
 }
 
-static int kho_test_prepare_fdt(struct kho_test_state *state)
+static int kho_test_preserve(struct kho_test_state *state)
 {
-	const char compatible[] = KHO_TEST_COMPAT;
-	unsigned int magic = KHO_TEST_MAGIC;
 	ssize_t fdt_size;
-	int err = 0;
-	void *fdt;
+	int err;
 
 	fdt_size = state->nr_folios * sizeof(phys_addr_t) + PAGE_SIZE;
 	state->fdt = folio_alloc(GFP_KERNEL, get_order(fdt_size));
 	if (!state->fdt)
 		return -ENOMEM;
 
-	fdt = folio_address(state->fdt);
+	err = kho_preserve_folio(state->fdt);
+	if (err)
+		goto err_free_fdt;
 
-	err |= kho_preserve_folio(state->fdt);
-	err |= fdt_create(fdt, fdt_size);
-	err |= fdt_finish_reservemap(fdt);
+	err = kho_test_preserve_data(state);
+	if (err)
+		goto err_unpreserve_fdt;
 
-	err |= fdt_begin_node(fdt, "");
-	err |= fdt_property(fdt, "compatible", compatible, sizeof(compatible));
-	err |= fdt_property(fdt, "magic", &magic, sizeof(magic));
-	err |= kho_test_save_data(state, fdt);
-	err |= fdt_end_node(fdt);
-
-	err |= fdt_finish(fdt);
+	err = kho_test_prepare_fdt(state, fdt_size);
+	if (err)
+		goto err_unpreserve_data;
 
 	err = kho_add_subtree(KHO_TEST_FDT, folio_address(state->fdt));
 	if (err)
-		folio_put(state->fdt);
+		goto err_unpreserve_data;
 
+	return 0;
+
+err_unpreserve_data:
+	kho_test_unpreserve_data(state);
+err_unpreserve_fdt:
+	kho_unpreserve_folio(state->fdt);
+err_free_fdt:
+	folio_put(state->fdt);
 	return err;
 }
 
@@ -174,14 +219,12 @@ static int kho_test_save(void)
 	if (err)
 		goto err_free_folios;
 
-	err = kho_test_prepare_fdt(state);
+	err = kho_test_preserve(state);
 	if (err)
 		goto err_free_folios;
 
 	return 0;
 
-err_free_fdt:
-	folio_put(state->fdt);
 err_free_folios:
 	kvfree(folios);
 	return err;