Introduce Virtio-loopback epsilon release:

Epsilon release introduces a new compatibility layer which make virtio-loopback
design to work with QEMU and rust-vmm vhost-user backend without require any
changes.

Signed-off-by: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
Change-Id: I52e57563e08a7d0bdc002f8e928ee61ba0c53dd9

1 files changed, 408 insertions, 0 deletions

diff --git a/tests/unit/test-bdrv-graph-mod.c b/tests/unit/test-bdrv-graph-mod.c
new file mode 100644
index 000000000..a6e3bb79b
--- /dev/null
+++ b/tests/unit/test-bdrv-graph-mod.c
@@ -0,0 +1,408 @@
+/*
+ * Block node graph modifications tests
+ *
+ * Copyright (c) 2019-2021 Virtuozzo International GmbH. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "qemu/main-loop.h"
+#include "block/block_int.h"
+#include "sysemu/block-backend.h"
+
+static BlockDriver bdrv_pass_through = {
+    .format_name = "pass-through",
+    .bdrv_child_perm = bdrv_default_perms,
+};
+
+static void no_perm_default_perms(BlockDriverState *bs, BdrvChild *c,
+                                         BdrvChildRole role,
+                                         BlockReopenQueue *reopen_queue,
+                                         uint64_t perm, uint64_t shared,
+                                         uint64_t *nperm, uint64_t *nshared)
+{
+    *nperm = 0;
+    *nshared = BLK_PERM_ALL;
+}
+
+static BlockDriver bdrv_no_perm = {
+    .format_name = "no-perm",
+    .supports_backing = true,
+    .bdrv_child_perm = no_perm_default_perms,
+};
+
+static void exclusive_write_perms(BlockDriverState *bs, BdrvChild *c,
+                                  BdrvChildRole role,
+                                  BlockReopenQueue *reopen_queue,
+                                  uint64_t perm, uint64_t shared,
+                                  uint64_t *nperm, uint64_t *nshared)
+{
+    *nperm = BLK_PERM_WRITE;
+    *nshared = BLK_PERM_ALL & ~BLK_PERM_WRITE;
+}
+
+static BlockDriver bdrv_exclusive_writer = {
+    .format_name = "exclusive-writer",
+    .bdrv_child_perm = exclusive_write_perms,
+};
+
+static BlockDriverState *no_perm_node(const char *name)
+{
+    return bdrv_new_open_driver(&bdrv_no_perm, name, BDRV_O_RDWR, &error_abort);
+}
+
+static BlockDriverState *pass_through_node(const char *name)
+{
+    return bdrv_new_open_driver(&bdrv_pass_through, name,
+                                BDRV_O_RDWR, &error_abort);
+}
+
+static BlockDriverState *exclusive_writer_node(const char *name)
+{
+    return bdrv_new_open_driver(&bdrv_exclusive_writer, name,
+                                BDRV_O_RDWR, &error_abort);
+}
+
+/*
+ * test_update_perm_tree
+ *
+ * When checking node for a possibility to update permissions, it's subtree
+ * should be correctly checked too. New permissions for each node should be
+ * calculated and checked in context of permissions of other nodes. If we
+ * check new permissions of the node only in context of old permissions of
+ * its neighbors, we can finish up with wrong permission graph.
+ *
+ * This test firstly create the following graph:
+ *                                +--------+
+ *                                |  root  |
+ *                                +--------+
+ *                                    |
+ *                                    | perm: write, read
+ *                                    | shared: except write
+ *                                    v
+ *  +-------------------+           +----------------+
+ *  | passtrough filter |---------->|  null-co node  |
+ *  +-------------------+           +----------------+
+ *
+ *
+ * and then, tries to append filter under node. Expected behavior: fail.
+ * Otherwise we'll get the following picture, with two BdrvChild'ren, having
+ * write permission to one node, without actually sharing it.
+ *
+ *                     +--------+
+ *                     |  root  |
+ *                     +--------+
+ *                         |
+ *                         | perm: write, read
+ *                         | shared: except write
+ *                         v
+ *                +-------------------+
+ *                | passtrough filter |
+ *                +-------------------+
+ *                       |   |
+ *     perm: write, read |   | perm: write, read
+ *  shared: except write |   | shared: except write
+ *                       v   v
+ *                +----------------+
+ *                |  null co node  |
+ *                +----------------+
+ */
+static void test_update_perm_tree(void)
+{
+    int ret;
+
+    BlockBackend *root = blk_new(qemu_get_aio_context(),
+                                 BLK_PERM_WRITE | BLK_PERM_CONSISTENT_READ,
+                                 BLK_PERM_ALL & ~BLK_PERM_WRITE);
+    BlockDriverState *bs = no_perm_node("node");
+    BlockDriverState *filter = pass_through_node("filter");
+
+    blk_insert_bs(root, bs, &error_abort);
+
+    bdrv_attach_child(filter, bs, "child", &child_of_bds,
+                      BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY, &error_abort);
+
+    ret = bdrv_append(filter, bs, NULL);
+    g_assert_cmpint(ret, <, 0);
+
+    bdrv_unref(filter);
+    blk_unref(root);
+}
+
+/*
+ * test_should_update_child
+ *
+ * Test that bdrv_replace_node, and concretely should_update_child
+ * do the right thing, i.e. not creating loops on the graph.
+ *
+ * The test does the following:
+ * 1. initial graph:
+ *
+ *   +------+          +--------+
+ *   | root |          | filter |
+ *   +------+          +--------+
+ *      |                  |
+ *  root|            target|
+ *      v                  v
+ *   +------+          +--------+
+ *   | node |<---------| target |
+ *   +------+  backing +--------+
+ *
+ * 2. Append @filter above @node. If should_update_child works correctly,
+ * it understands, that backing child of @target should not be updated,
+ * as it will create a loop on node graph. Resulting picture should
+ * be the left one, not the right:
+ *
+ *     +------+                            +------+
+ *     | root |                            | root |
+ *     +------+                            +------+
+ *        |                                   |
+ *    root|                               root|
+ *        v                                   v
+ *    +--------+   target                 +--------+   target
+ *    | filter |--------------+           | filter |--------------+
+ *    +--------+              |           +--------+              |
+ *        |                   |               |  ^                v
+ * backing|                   |        backing|  |           +--------+
+ *        v                   v               |  +-----------| target |
+ *     +------+          +--------+           v      backing +--------+
+ *     | node |<---------| target |        +------+
+ *     +------+  backing +--------+        | node |
+ *                                         +------+
+ *
+ *    (good picture)                       (bad picture)
+ *
+ */
+static void test_should_update_child(void)
+{
+    BlockBackend *root = blk_new(qemu_get_aio_context(), 0, BLK_PERM_ALL);
+    BlockDriverState *bs = no_perm_node("node");
+    BlockDriverState *filter = no_perm_node("filter");
+    BlockDriverState *target = no_perm_node("target");
+
+    blk_insert_bs(root, bs, &error_abort);
+
+    bdrv_set_backing_hd(target, bs, &error_abort);
+
+    g_assert(target->backing->bs == bs);
+    bdrv_attach_child(filter, target, "target", &child_of_bds,
+                      BDRV_CHILD_DATA, &error_abort);
+    bdrv_append(filter, bs, &error_abort);
+    g_assert(target->backing->bs == bs);
+
+    bdrv_unref(filter);
+    bdrv_unref(bs);
+    blk_unref(root);
+}
+
+/*
+ * test_parallel_exclusive_write
+ *
+ * Check that when we replace node, old permissions of the node being removed
+ * doesn't break the replacement.
+ */
+static void test_parallel_exclusive_write(void)
+{
+    BlockDriverState *top = exclusive_writer_node("top");
+    BlockDriverState *base = no_perm_node("base");
+    BlockDriverState *fl1 = pass_through_node("fl1");
+    BlockDriverState *fl2 = pass_through_node("fl2");
+
+    /*
+     * bdrv_attach_child() eats child bs reference, so we need two @base
+     * references for two filters:
+     */
+    bdrv_ref(base);
+
+    bdrv_attach_child(top, fl1, "backing", &child_of_bds, BDRV_CHILD_DATA,
+                      &error_abort);
+    bdrv_attach_child(fl1, base, "backing", &child_of_bds, BDRV_CHILD_FILTERED,
+                      &error_abort);
+    bdrv_attach_child(fl2, base, "backing", &child_of_bds, BDRV_CHILD_FILTERED,
+                      &error_abort);
+
+    bdrv_replace_node(fl1, fl2, &error_abort);
+
+    bdrv_unref(fl2);
+    bdrv_unref(top);
+}
+
+static void write_to_file_perms(BlockDriverState *bs, BdrvChild *c,
+                                     BdrvChildRole role,
+                                     BlockReopenQueue *reopen_queue,
+                                     uint64_t perm, uint64_t shared,
+                                     uint64_t *nperm, uint64_t *nshared)
+{
+    if (bs->file && c == bs->file) {
+        *nperm = BLK_PERM_WRITE;
+        *nshared = BLK_PERM_ALL & ~BLK_PERM_WRITE;
+    } else {
+        *nperm = 0;
+        *nshared = BLK_PERM_ALL;
+    }
+}
+
+static BlockDriver bdrv_write_to_file = {
+    .format_name = "tricky-perm",
+    .bdrv_child_perm = write_to_file_perms,
+};
+
+
+/*
+ * The following test shows that topological-sort order is required for
+ * permission update, simple DFS is not enough.
+ *
+ * Consider the block driver which has two filter children: one active
+ * with exclusive write access and one inactive with no specific
+ * permissions.
+ *
+ * And, these two children has a common base child, like this:
+ *
+ * ┌─────┐     ┌──────┐
+ * │ fl2 │ ◀── │ top  │
+ * └─────┘     └──────┘
+ *   │           │
+ *   │           │ w
+ *   │           ▼
+ *   │         ┌──────┐
+ *   │         │ fl1  │
+ *   │         └──────┘
+ *   │           │
+ *   │           │ w
+ *   │           ▼
+ *   │         ┌──────┐
+ *   └───────▶ │ base │
+ *             └──────┘
+ *
+ * So, exclusive write is propagated.
+ *
+ * Assume, we want to make fl2 active instead of fl1.
+ * So, we set some option for top driver and do permission update.
+ *
+ * With simple DFS, if permission update goes first through
+ * top->fl1->base branch it will succeed: it firstly drop exclusive write
+ * permissions and than apply them for another BdrvChildren.
+ * But if permission update goes first through top->fl2->base branch it
+ * will fail, as when we try to update fl2->base child, old not yet
+ * updated fl1->base child will be in conflict.
+ *
+ * With topological-sort order we always update parents before children, so fl1
+ * and fl2 are both updated when we update base and there is no conflict.
+ */
+static void test_parallel_perm_update(void)
+{
+    BlockDriverState *top = no_perm_node("top");
+    BlockDriverState *tricky =
+            bdrv_new_open_driver(&bdrv_write_to_file, "tricky", BDRV_O_RDWR,
+                                 &error_abort);
+    BlockDriverState *base = no_perm_node("base");
+    BlockDriverState *fl1 = pass_through_node("fl1");
+    BlockDriverState *fl2 = pass_through_node("fl2");
+    BdrvChild *c_fl1, *c_fl2;
+
+    /*
+     * bdrv_attach_child() eats child bs reference, so we need two @base
+     * references for two filters:
+     */
+    bdrv_ref(base);
+
+    bdrv_attach_child(top, tricky, "file", &child_of_bds, BDRV_CHILD_DATA,
+                      &error_abort);
+    c_fl1 = bdrv_attach_child(tricky, fl1, "first", &child_of_bds,
+                              BDRV_CHILD_FILTERED, &error_abort);
+    c_fl2 = bdrv_attach_child(tricky, fl2, "second", &child_of_bds,
+                              BDRV_CHILD_FILTERED, &error_abort);
+    bdrv_attach_child(fl1, base, "backing", &child_of_bds, BDRV_CHILD_FILTERED,
+                      &error_abort);
+    bdrv_attach_child(fl2, base, "backing", &child_of_bds, BDRV_CHILD_FILTERED,
+                      &error_abort);
+
+    /* Select fl1 as first child to be active */
+    tricky->file = c_fl1;
+    bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort);
+
+    assert(c_fl1->perm & BLK_PERM_WRITE);
+    assert(!(c_fl2->perm & BLK_PERM_WRITE));
+
+    /* Now, try to switch active child and update permissions */
+    tricky->file = c_fl2;
+    bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort);
+
+    assert(c_fl2->perm & BLK_PERM_WRITE);
+    assert(!(c_fl1->perm & BLK_PERM_WRITE));
+
+    /* Switch once more, to not care about real child order in the list */
+    tricky->file = c_fl1;
+    bdrv_child_refresh_perms(top, top->children.lh_first, &error_abort);
+
+    assert(c_fl1->perm & BLK_PERM_WRITE);
+    assert(!(c_fl2->perm & BLK_PERM_WRITE));
+
+    bdrv_unref(top);
+}
+
+/*
+ * It's possible that filter required permissions allows to insert it to backing
+ * chain, like:
+ *
+ *  1.  [top] -> [filter] -> [base]
+ *
+ * but doesn't allow to add it as a branch:
+ *
+ *  2.  [filter] --\
+ *                 v
+ *      [top] -> [base]
+ *
+ * So, inserting such filter should do all graph modifications and only then
+ * update permissions. If we try to go through intermediate state [2] and update
+ * permissions on it we'll fail.
+ *
+ * Let's check that bdrv_append() can append such a filter.
+ */
+static void test_append_greedy_filter(void)
+{
+    BlockDriverState *top = exclusive_writer_node("top");
+    BlockDriverState *base = no_perm_node("base");
+    BlockDriverState *fl = exclusive_writer_node("fl1");
+
+    bdrv_attach_child(top, base, "backing", &child_of_bds, BDRV_CHILD_COW,
+                      &error_abort);
+
+    bdrv_append(fl, base, &error_abort);
+    bdrv_unref(fl);
+    bdrv_unref(top);
+}
+
+int main(int argc, char *argv[])
+{
+    bdrv_init();
+    qemu_init_main_loop(&error_abort);
+
+    g_test_init(&argc, &argv, NULL);
+
+    g_test_add_func("/bdrv-graph-mod/update-perm-tree", test_update_perm_tree);
+    g_test_add_func("/bdrv-graph-mod/should-update-child",
+                    test_should_update_child);
+    g_test_add_func("/bdrv-graph-mod/parallel-perm-update",
+                    test_parallel_perm_update);
+    g_test_add_func("/bdrv-graph-mod/parallel-exclusive-write",
+                    test_parallel_exclusive_write);
+    g_test_add_func("/bdrv-graph-mod/append-greedy-filter",
+                    test_append_greedy_filter);
+
+    return g_test_run();
+}