block: Rewrite the snapshot authorization mechanism for block filters.

This patch keep the recursive way of doing things but simplify it by giving
two responsabilities to all block filters implementors.

They will need to do two things:

-Set the is_filter field of their block driver to true.

-Implement the bdrv_recurse_is_first_non_filter method of their block driver like
it is done on the Quorum block driver. (block/quorum.c)

[Paolo Bonzini <pbonzini@redhat.com> pointed out that this patch changes
the semantics of blkverify, which now recurses down both bs->file and
s->test_file.
-- Stefan]

Reported-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

2 files changed, 17 insertions, 3 deletions

diff --git a/block/blkverify.c b/block/blkverify.c
index b98b08b..e1c3117 100644
--- a/block/blkverify.c
+++ b/block/blkverify.c
@@ -288,6 +288,20 @@ static BlockDriverAIOCB *blkverify_aio_flush(BlockDriverState *bs,
     return bdrv_aio_flush(s->test_file, cb, opaque);
 }
 
+static bool blkverify_recurse_is_first_non_filter(BlockDriverState *bs,
+                                                  BlockDriverState *candidate)
+{
+    BDRVBlkverifyState *s = bs->opaque;
+
+    bool perm = bdrv_recurse_is_first_non_filter(bs->file, candidate);
+
+    if (perm) {
+        return true;
+    }
+
+    return bdrv_recurse_is_first_non_filter(s->test_file, candidate);
+}
+
 static BlockDriver bdrv_blkverify = {
     .format_name            = "blkverify",
     .protocol_name          = "blkverify",
@@ -302,7 +316,8 @@ static BlockDriver bdrv_blkverify = {
     .bdrv_aio_writev        = blkverify_aio_writev,
     .bdrv_aio_flush         = blkverify_aio_flush,
 
-    .authorizations         = { true, false },
+    .is_filter              = true,
+    .bdrv_recurse_is_first_non_filter = blkverify_recurse_is_first_non_filter,
 };
 
 static void bdrv_blkverify_init(void)
diff --git a/block/quorum.c b/block/quorum.c
index bd997b7..33bf2ae 100644
--- a/block/quorum.c
+++ b/block/quorum.c
@@ -852,8 +852,6 @@ static BlockDriver bdrv_quorum = {
     .bdrv_file_open     = quorum_open,
     .bdrv_close         = quorum_close,
 
-    .authorizations     = { true, true },
-
     .bdrv_co_flush_to_disk = quorum_co_flush,
 
     .bdrv_getlength     = quorum_getlength,
@@ -862,6 +860,7 @@ static BlockDriver bdrv_quorum = {
     .bdrv_aio_writev    = quorum_aio_writev,
     .bdrv_invalidate_cache = quorum_invalidate_cache,
 
+    .is_filter           = true,
     .bdrv_recurse_is_first_non_filter = quorum_recurse_is_first_non_filter,
 };