diff mbox

[26/34] block: reopen: Document option precedence and refactor accordingly

Message ID 1431105726-3682-27-git-send-email-kwolf@redhat.com
State New
Headers show

Commit Message

Kevin Wolf May 8, 2015, 5:21 p.m. UTC
The interesting part of reopening an image is from which sources the
effective options should be taken, i.e. which options take precedence
over which other options. This patch documents the precedence that will
be implemented in the following patches.

It also refactors bdrv_reopen_queue(), so that the top-level reopened
node is handled the same way as children are. Option/flag inheritance
from the parent becomes just one item in the list and is done at the
beginning of the function, similar to how the other items are/will be
handled.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block.c | 39 +++++++++++++++++++++++++++++++++------
 1 file changed, 33 insertions(+), 6 deletions(-)

Comments

Max Reitz May 13, 2015, 2:47 p.m. UTC | #1
On 08.05.2015 19:21, Kevin Wolf wrote:
> The interesting part of reopening an image is from which sources the
> effective options should be taken, i.e. which options take precedence
> over which other options. This patch documents the precedence that will
> be implemented in the following patches.
>
> It also refactors bdrv_reopen_queue(), so that the top-level reopened
> node is handled the same way as children are. Option/flag inheritance
> from the parent becomes just one item in the list and is done at the
> beginning of the function, similar to how the other items are/will be
> handled.
>
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>   block.c | 39 +++++++++++++++++++++++++++++++++------
>   1 file changed, 33 insertions(+), 6 deletions(-)

Reviewed-by: Max Reitz <mreitz@redhat.com>
diff mbox

Patch

diff --git a/block.c b/block.c
index 8a31d62..1e5625f 100644
--- a/block.c
+++ b/block.c
@@ -1617,9 +1617,13 @@  typedef struct BlockReopenQueueEntry {
  * bs_queue, or the existing bs_queue being used.
  *
  */
-BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,
-                                    BlockDriverState *bs,
-                                    QDict *options, int flags)
+static BlockReopenQueue *bdrv_reopen_queue_child(BlockReopenQueue *bs_queue,
+                                                 BlockDriverState *bs,
+                                                 QDict *options,
+                                                 int flags,
+                                                 const BdrvChildRole *role,
+                                                 QDict *parent_options,
+                                                 int parent_flags)
 {
     assert(bs != NULL);
 
@@ -1636,6 +1640,22 @@  BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,
         options = qdict_new();
     }
 
+    /*
+     * Precedence of options:
+     * 1. Explicitly passed in options (highest)
+     * 2. TODO Set in flags (only for top level)
+     * 3. TODO Retained from explicitly set options of bs
+     * 4. TODO Inherited from parent node
+     * 5. Retained from effective options of bs
+     */
+
+    /* Inherit from parent node */
+    if (parent_options) {
+        assert(!flags);
+        flags = role->inherit_flags(parent_flags);
+    }
+
+    /* Old values are used for options that aren't set yet */
     old_options = qdict_clone_shallow(bs->options);
     qdict_join(options, old_options, false);
     QDECREF(old_options);
@@ -1646,7 +1666,6 @@  BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,
     QLIST_FOREACH(child, &bs->children, next) {
         QDict *new_child_options;
         char *child_key_dot;
-        int child_flags;
 
         /* reopen can only change the options of block devices that were
          * implicitly created and inherited options. For other (referenced)
@@ -1659,8 +1678,8 @@  BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,
         qdict_extract_subqdict(options, &new_child_options, child_key_dot);
         g_free(child_key_dot);
 
-        child_flags = child->role->inherit_flags(flags);
-        bdrv_reopen_queue(bs_queue, child->bs, new_child_options, child_flags);
+        bdrv_reopen_queue_child(bs_queue, child->bs, new_child_options, 0,
+                                child->role, options, flags);
     }
 
     bs_entry = g_new0(BlockReopenQueueEntry, 1);
@@ -1673,6 +1692,14 @@  BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,
     return bs_queue;
 }
 
+BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,
+                                    BlockDriverState *bs,
+                                    QDict *options, int flags)
+{
+    return bdrv_reopen_queue_child(bs_queue, bs, options, flags,
+                                   NULL, NULL, 0);
+}
+
 /*
  * Reopen multiple BlockDriverStates atomically & transactionally.
  *