[Qemu-devel] [PATCH v3 16/38] block: Add BlockBackendRootState

[Max Reitz <mreitz@redhat.com>]

This structure will store some of the state of the root BDS if the BDS
tree is removed, so that state can be restored once a new BDS tree is
inserted.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
---
 block/block-backend.c          | 26 ++++++++++++++++++++++++++
 include/block/block_int.h      |  9 +++++++++
 include/qemu/typedefs.h        |  1 +
 include/sysemu/block-backend.h |  2 ++
 4 files changed, 38 insertions(+)

diff --git a/block/block-backend.c b/block/block-backend.c
index 254b19f..bef09af 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -37,6 +37,10 @@ struct BlockBackend {
     /* the block size for which the guest device expects atomicity */
     int guest_block_size;
 
+    /* If the BDS tree is removed, some of its options are stored here (which
+     * can be used to restore those options in the new BDS on insert) */
+    BlockBackendRootState root_state;
+
     /* I/O stats (display with "info blockstats"). */
     BlockAcctStats stats;
 
@@ -1045,3 +1049,25 @@ int blk_probe_geometry(BlockBackend *blk, HDGeometry *geo)
 {
     return bdrv_probe_geometry(blk->bs, geo);
 }
+
+/*
+ * Updates the BlockBackendRootState object with data from the currently
+ * attached BlockDriverState.
+ */
+void blk_update_root_state(BlockBackend *blk)
+{
+    assert(blk->bs);
+
+    blk->root_state.open_flags    = blk->bs->open_flags;
+    blk->root_state.read_only     = blk->bs->read_only;
+    blk->root_state.detect_zeroes = blk->bs->detect_zeroes;
+
+    blk->root_state.io_limits_enabled = blk->bs->io_limits_enabled;
+    throttle_get_config(&blk->bs->throttle_state,
+                        &blk->root_state.throttle_config);
+}
+
+BlockBackendRootState *blk_get_root_state(BlockBackend *blk)
+{
+    return &blk->root_state;
+}
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 5ea9e6d..b5c08ec 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -426,6 +426,15 @@ struct BlockDriverState {
     NotifierWithReturn write_threshold_notifier;
 };
 
+struct BlockBackendRootState {
+    int open_flags;
+    bool read_only;
+    BlockdevDetectZeroesOptions detect_zeroes;
+
+    bool io_limits_enabled;
+    ThrottleConfig throttle_config;
+};
+
 
 /* Essential block drivers which must always be statically linked into qemu, and
  * which therefore can be accessed without using bdrv_find_format() */
diff --git a/include/qemu/typedefs.h b/include/qemu/typedefs.h
index cde3314..39a95dd 100644
--- a/include/qemu/typedefs.h
+++ b/include/qemu/typedefs.h
@@ -11,6 +11,7 @@ typedef struct AddressSpace AddressSpace;
 typedef struct AioContext AioContext;
 typedef struct AudioState AudioState;
 typedef struct BlockBackend BlockBackend;
+typedef struct BlockBackendRootState BlockBackendRootState;
 typedef struct BlockDriverState BlockDriverState;
 typedef struct BusClass BusClass;
 typedef struct BusState BusState;
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index d38553c..b98a86e 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -162,6 +162,8 @@ void blk_add_close_notifier(BlockBackend *blk, Notifier *notify);
 void blk_io_plug(BlockBackend *blk);
 void blk_io_unplug(BlockBackend *blk);
 BlockAcctStats *blk_get_stats(BlockBackend *blk);
+BlockBackendRootState *blk_get_root_state(BlockBackend *blk);
+void blk_update_root_state(BlockBackend *blk);
 
 void *blk_aio_get(const AIOCBInfo *aiocb_info, BlockBackend *blk,
                   BlockCompletionFunc *cb, void *opaque);
-- 
2.4.1