[PATCH v8 0/4] block: small refactorings

[PATCH v8 0/4] block: small refactorings

[Vladimir Sementsov-Ogievskiy]

Hi all!

Here is 4-more simple already reviewed patches from
 "[PATCH v5 00/45] Transactional block-graph modifying API" [1]

Called v8 because first part of [1] was recently merged as
 "[PATCH v7 for-7.2 00/15] block: cleanup backing and file handling"

Vladimir Sementsov-Ogievskiy (4):
  block: drop bdrv_detach_child()
  block: drop bdrv_remove_filter_or_cow_child
  block: bdrv_refresh_perms(): allow external tran
  block: refactor bdrv_list_refresh_perms to allow any list of nodes

 block.c | 141 ++++++++++++++++++++++++++++----------------------------
 1 file changed, 71 insertions(+), 70 deletions(-)

-- 
2.34.1

[PATCH v8 1/4] block: drop bdrv_detach_child()

[Vladimir Sementsov-Ogievskiy]

From: Vladimir Sementsov-Ogievskiy <vladimir.sementsov-ogievskiy@openvz.org>

The only caller is bdrv_root_unref_child(), let's just do the logic
directly in it. It simplifies further convertion of
bdrv_root_unref_child() to transaction action.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@openvz.org>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
---
 block.c | 46 +++++++++++++++++++---------------------------
 1 file changed, 19 insertions(+), 27 deletions(-)

diff --git a/block.c b/block.c
index 3bd594eb2a..65f5bb96ed 100644
--- a/block.c
+++ b/block.c
@@ -3060,30 +3060,6 @@ static BdrvChild *bdrv_attach_child_noperm(BlockDriverState *parent_bs,
                                     tran, errp);
 }
 
-static void bdrv_detach_child(BdrvChild *child)
-{
-    BlockDriverState *old_bs = child->bs;
-
-    GLOBAL_STATE_CODE();
-    bdrv_replace_child_noperm(child, NULL);
-    bdrv_child_free(child);
-
-    if (old_bs) {
-        /*
-         * Update permissions for old node. We're just taking a parent away, so
-         * we're loosening restrictions. Errors of permission update are not
-         * fatal in this case, ignore them.
-         */
-        bdrv_refresh_perms(old_bs, NULL);
-
-        /*
-         * When the parent requiring a non-default AioContext is removed, the
-         * node moves back to the main AioContext
-         */
-        bdrv_try_change_aio_context(old_bs, qemu_get_aio_context(), NULL, NULL);
-    }
-}
-
 /*
  * This function steals the reference to child_bs from the caller.
  * That reference is later dropped by bdrv_root_unref_child().
@@ -3172,12 +3148,28 @@ out:
 /* Callers must ensure that child->frozen is false. */
 void bdrv_root_unref_child(BdrvChild *child)
 {
-    BlockDriverState *child_bs;
+    BlockDriverState *child_bs = child->bs;
 
     GLOBAL_STATE_CODE();
+    bdrv_replace_child_noperm(child, NULL);
+    bdrv_child_free(child);
+
+    if (child_bs) {
+        /*
+         * Update permissions for old node. We're just taking a parent away, so
+         * we're loosening restrictions. Errors of permission update are not
+         * fatal in this case, ignore them.
+         */
+        bdrv_refresh_perms(child_bs, NULL);
+
+        /*
+         * When the parent requiring a non-default AioContext is removed, the
+         * node moves back to the main AioContext
+         */
+        bdrv_try_change_aio_context(child_bs, qemu_get_aio_context(), NULL,
+                                    NULL);
+    }
 
-    child_bs = child->bs;
-    bdrv_detach_child(child);
     bdrv_unref(child_bs);
 }
 
-- 
2.34.1

[PATCH v8 2/4] block: drop bdrv_remove_filter_or_cow_child

[Vladimir Sementsov-Ogievskiy]

From: Vladimir Sementsov-Ogievskiy <vladimir.sementsov-ogievskiy@openvz.org>

Drop this simple wrapper used only in one place. We have too many graph
modifying functions even without it.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@openvz.org>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
---
 block.c | 15 +--------------
 1 file changed, 1 insertion(+), 14 deletions(-)

diff --git a/block.c b/block.c
index 65f5bb96ed..8acff7983d 100644
--- a/block.c
+++ b/block.c
@@ -93,8 +93,6 @@ static bool bdrv_recurse_has_child(BlockDriverState *bs,
 static void bdrv_replace_child_noperm(BdrvChild *child,
                                       BlockDriverState *new_bs);
 static void bdrv_remove_child(BdrvChild *child, Transaction *tran);
-static void bdrv_remove_filter_or_cow_child(BlockDriverState *bs,
-                                            Transaction *tran);
 
 static int bdrv_reopen_prepare(BDRVReopenState *reopen_state,
                                BlockReopenQueue *queue,
@@ -5055,17 +5053,6 @@ static void bdrv_remove_child(BdrvChild *child, Transaction *tran)
     tran_add(tran, &bdrv_remove_child_drv, child);
 }
 
-/*
- * A function to remove backing-chain child of @bs if exists: cow child for
- * format nodes (always .backing) and filter child for filters (may be .file or
- * .backing)
- */
-static void bdrv_remove_filter_or_cow_child(BlockDriverState *bs,
-                                            Transaction *tran)
-{
-    bdrv_remove_child(bdrv_filter_or_cow_child(bs), tran);
-}
-
 static int bdrv_replace_node_noperm(BlockDriverState *from,
                                     BlockDriverState *to,
                                     bool auto_skip, Transaction *tran,
@@ -5150,7 +5137,7 @@ static int bdrv_replace_node_common(BlockDriverState *from,
     }
 
     if (detach_subchain) {
-        bdrv_remove_filter_or_cow_child(to_cow_parent, tran);
+        bdrv_remove_child(bdrv_filter_or_cow_child(to_cow_parent), tran);
     }
 
     found = g_hash_table_new(NULL, NULL);
-- 
2.34.1

[PATCH v8 3/4] block: bdrv_refresh_perms(): allow external tran

[Vladimir Sementsov-Ogievskiy]

From: Vladimir Sementsov-Ogievskiy <vladimir.sementsov-ogievskiy@openvz.org>

Allow passing external Transaction pointer, stop creating extra
Transaction objects.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@openvz.org>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
---
 block.c | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/block.c b/block.c
index 8acff7983d..eed54f968d 100644
--- a/block.c
+++ b/block.c
@@ -2581,15 +2581,24 @@ char *bdrv_perm_names(uint64_t perm)
 }
 
 
-static int bdrv_refresh_perms(BlockDriverState *bs, Error **errp)
+/* @tran is allowed to be NULL. In this case no rollback is possible */
+static int bdrv_refresh_perms(BlockDriverState *bs, Transaction *tran,
+                              Error **errp)
 {
     int ret;
-    Transaction *tran = tran_new();
+    Transaction *local_tran = NULL;
     g_autoptr(GSList) list = bdrv_topological_dfs(NULL, NULL, bs);
     GLOBAL_STATE_CODE();
 
+    if (!tran) {
+        tran = local_tran = tran_new();
+    }
+
     ret = bdrv_list_refresh_perms(list, NULL, tran, errp);
-    tran_finalize(tran, ret);
+
+    if (local_tran) {
+        tran_finalize(local_tran, ret);
+    }
 
     return ret;
 }
@@ -2605,7 +2614,7 @@ int bdrv_child_try_set_perm(BdrvChild *c, uint64_t perm, uint64_t shared,
 
     bdrv_child_set_perm(c, perm, shared, tran);
 
-    ret = bdrv_refresh_perms(c->bs, &local_err);
+    ret = bdrv_refresh_perms(c->bs, tran, &local_err);
 
     tran_finalize(tran, ret);
 
@@ -3089,7 +3098,7 @@ BdrvChild *bdrv_root_attach_child(BlockDriverState *child_bs,
         goto out;
     }
 
-    ret = bdrv_refresh_perms(child_bs, errp);
+    ret = bdrv_refresh_perms(child_bs, tran, errp);
 
 out:
     tran_finalize(tran, ret);
@@ -3130,7 +3139,7 @@ BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs,
         goto out;
     }
 
-    ret = bdrv_refresh_perms(parent_bs, errp);
+    ret = bdrv_refresh_perms(parent_bs, tran, errp);
     if (ret < 0) {
         goto out;
     }
@@ -3158,7 +3167,7 @@ void bdrv_root_unref_child(BdrvChild *child)
          * we're loosening restrictions. Errors of permission update are not
          * fatal in this case, ignore them.
          */
-        bdrv_refresh_perms(child_bs, NULL);
+        bdrv_refresh_perms(child_bs, NULL, NULL);
 
         /*
          * When the parent requiring a non-default AioContext is removed, the
@@ -3400,7 +3409,7 @@ int bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd,
         goto out;
     }
 
-    ret = bdrv_refresh_perms(bs, errp);
+    ret = bdrv_refresh_perms(bs, tran, errp);
 out:
     tran_finalize(tran, ret);
 
@@ -5213,7 +5222,7 @@ int bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top,
         goto out;
     }
 
-    ret = bdrv_refresh_perms(bs_new, errp);
+    ret = bdrv_refresh_perms(bs_new, tran, errp);
 out:
     tran_finalize(tran, ret);
 
@@ -6513,7 +6522,7 @@ int bdrv_activate(BlockDriverState *bs, Error **errp)
      */
     if (bs->open_flags & BDRV_O_INACTIVE) {
         bs->open_flags &= ~BDRV_O_INACTIVE;
-        ret = bdrv_refresh_perms(bs, errp);
+        ret = bdrv_refresh_perms(bs, NULL, errp);
         if (ret < 0) {
             bs->open_flags |= BDRV_O_INACTIVE;
             return ret;
@@ -6658,7 +6667,7 @@ static int bdrv_inactivate_recurse(BlockDriverState *bs)
      * We only tried to loosen restrictions, so errors are not fatal, ignore
      * them.
      */
-    bdrv_refresh_perms(bs, NULL);
+    bdrv_refresh_perms(bs, NULL, NULL);
 
     /* Recursively inactivate children */
     QLIST_FOREACH(child, &bs->children, next) {
-- 
2.34.1

[PATCH v8 4/4] block: refactor bdrv_list_refresh_perms to allow any list of nodes

[Vladimir Sementsov-Ogievskiy]

From: Vladimir Sementsov-Ogievskiy <vladimir.sementsov-ogievskiy@openvz.org>

We are going to increase usage of collecting nodes in a list to then
update, and calling bdrv_topological_dfs() each time is not convenient,
and not correct as we are going to interleave graph modifying with
filling the node list.

So, let's switch to a function that takes any list of nodes, adds all
their subtrees and do topological sort. And finally, refresh
permissions.

While being here, make the function public, as we'll want to use it
from blockdev.c in near future.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@openvz.org>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
---
 block.c | 51 ++++++++++++++++++++++++++++++++-------------------
 1 file changed, 32 insertions(+), 19 deletions(-)

diff --git a/block.c b/block.c
index eed54f968d..4e039ee220 100644
--- a/block.c
+++ b/block.c
@@ -2511,8 +2511,12 @@ static int bdrv_node_refresh_perm(BlockDriverState *bs, BlockReopenQueue *q,
     return 0;
 }
 
-static int bdrv_list_refresh_perms(GSList *list, BlockReopenQueue *q,
-                                   Transaction *tran, Error **errp)
+/*
+ * @list is a product of bdrv_topological_dfs() (may be called several times) -
+ * a topologically sorted subgraph.
+ */
+static int bdrv_do_refresh_perms(GSList *list, BlockReopenQueue *q,
+                                 Transaction *tran, Error **errp)
 {
     int ret;
     BlockDriverState *bs;
@@ -2534,6 +2538,24 @@ static int bdrv_list_refresh_perms(GSList *list, BlockReopenQueue *q,
     return 0;
 }
 
+/*
+ * @list is any list of nodes. List is completed by all subtrees and
+ * topologically sorted. It's not a problem if some node occurs in the @list
+ * several times.
+ */
+static int bdrv_list_refresh_perms(GSList *list, BlockReopenQueue *q,
+                                   Transaction *tran, Error **errp)
+{
+    g_autoptr(GHashTable) found = g_hash_table_new(NULL, NULL);
+    g_autoptr(GSList) refresh_list = NULL;
+
+    for ( ; list; list = list->next) {
+        refresh_list = bdrv_topological_dfs(refresh_list, found, list->data);
+    }
+
+    return bdrv_do_refresh_perms(refresh_list, q, tran, errp);
+}
+
 void bdrv_get_cumulative_perm(BlockDriverState *bs, uint64_t *perm,
                               uint64_t *shared_perm)
 {
@@ -2594,7 +2616,7 @@ static int bdrv_refresh_perms(BlockDriverState *bs, Transaction *tran,
         tran = local_tran = tran_new();
     }
 
-    ret = bdrv_list_refresh_perms(list, NULL, tran, errp);
+    ret = bdrv_do_refresh_perms(list, NULL, tran, errp);
 
     if (local_tran) {
         tran_finalize(local_tran, ret);
@@ -4350,7 +4372,6 @@ int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp)
     BlockReopenQueueEntry *bs_entry, *next;
     AioContext *ctx;
     Transaction *tran = tran_new();
-    g_autoptr(GHashTable) found = NULL;
     g_autoptr(GSList) refresh_list = NULL;
 
     assert(qemu_get_current_aio_context() == qemu_get_aio_context());
@@ -4380,18 +4401,15 @@ int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp)
         bs_entry->prepared = true;
     }
 
-    found = g_hash_table_new(NULL, NULL);
     QTAILQ_FOREACH(bs_entry, bs_queue, entry) {
         BDRVReopenState *state = &bs_entry->state;
 
-        refresh_list = bdrv_topological_dfs(refresh_list, found, state->bs);
+        refresh_list = g_slist_prepend(refresh_list, state->bs);
         if (state->old_backing_bs) {
-            refresh_list = bdrv_topological_dfs(refresh_list, found,
-                                                state->old_backing_bs);
+            refresh_list = g_slist_prepend(refresh_list, state->old_backing_bs);
         }
         if (state->old_file_bs) {
-            refresh_list = bdrv_topological_dfs(refresh_list, found,
-                                                state->old_file_bs);
+            refresh_list = g_slist_prepend(refresh_list, state->old_file_bs);
         }
     }
 
@@ -5108,7 +5126,6 @@ static int bdrv_replace_node_common(BlockDriverState *from,
                                     Error **errp)
 {
     Transaction *tran = tran_new();
-    g_autoptr(GHashTable) found = NULL;
     g_autoptr(GSList) refresh_list = NULL;
     BlockDriverState *to_cow_parent = NULL;
     int ret;
@@ -5149,10 +5166,8 @@ static int bdrv_replace_node_common(BlockDriverState *from,
         bdrv_remove_child(bdrv_filter_or_cow_child(to_cow_parent), tran);
     }
 
-    found = g_hash_table_new(NULL, NULL);
-
-    refresh_list = bdrv_topological_dfs(refresh_list, found, to);
-    refresh_list = bdrv_topological_dfs(refresh_list, found, from);
+    refresh_list = g_slist_prepend(refresh_list, to);
+    refresh_list = g_slist_prepend(refresh_list, from);
 
     ret = bdrv_list_refresh_perms(refresh_list, NULL, tran, errp);
     if (ret < 0) {
@@ -5237,7 +5252,6 @@ int bdrv_replace_child_bs(BdrvChild *child, BlockDriverState *new_bs,
 {
     int ret;
     Transaction *tran = tran_new();
-    g_autoptr(GHashTable) found = NULL;
     g_autoptr(GSList) refresh_list = NULL;
     BlockDriverState *old_bs = child->bs;
 
@@ -5249,9 +5263,8 @@ int bdrv_replace_child_bs(BdrvChild *child, BlockDriverState *new_bs,
 
     bdrv_replace_child_tran(child, new_bs, tran);
 
-    found = g_hash_table_new(NULL, NULL);
-    refresh_list = bdrv_topological_dfs(refresh_list, found, old_bs);
-    refresh_list = bdrv_topological_dfs(refresh_list, found, new_bs);
+    refresh_list = g_slist_prepend(refresh_list, old_bs);
+    refresh_list = g_slist_prepend(refresh_list, new_bs);
 
     ret = bdrv_list_refresh_perms(refresh_list, NULL, tran, errp);
 
-- 
2.34.1

Re: [PATCH v8 0/4] block: small refactorings

[Kevin Wolf]

Am 07.11.2022 um 17:35 hat Vladimir Sementsov-Ogievskiy geschrieben:
> Hi all!
> 
> Here is 4-more simple already reviewed patches from
>  "[PATCH v5 00/45] Transactional block-graph modifying API" [1]
> 
> Called v8 because first part of [1] was recently merged as
>  "[PATCH v7 for-7.2 00/15] block: cleanup backing and file handling"

Thanks, applied to block-next.

Kevin