block: Add BlockBackend.ctx

This adds a new parameter to blk_new() which requires its callers to
declare from which AioContext this BlockBackend is going to be used (or
the locks of which AioContext need to be taken anyway).

The given context is only stored and kept up to date when changing
AioContexts. Actually applying the stored AioContext to the root node
is saved for another commit.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 15 insertions, 3 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index 390fde6f71..f03f14acb0 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -42,6 +42,7 @@ struct BlockBackend {
     char *name;
     int refcnt;
     BdrvChild *root;
+    AioContext *ctx;
     DriveInfo *legacy_dinfo;    /* null unless created by drive_new() */
     QTAILQ_ENTRY(BlockBackend) link;         /* for block_backends */
     QTAILQ_ENTRY(BlockBackend) monitor_link; /* for monitor_block_backends */
@@ -322,12 +323,13 @@ static const BdrvChildRole child_root = {
  *
  * Return the new BlockBackend on success, null on failure.
  */
-BlockBackend *blk_new(uint64_t perm, uint64_t shared_perm)
+BlockBackend *blk_new(AioContext *ctx, uint64_t perm, uint64_t shared_perm)
 {
     BlockBackend *blk;
 
     blk = g_new0(BlockBackend, 1);
     blk->refcnt = 1;
+    blk->ctx = ctx;
     blk->perm = perm;
     blk->shared_perm = shared_perm;
     blk_set_enable_write_cache(blk, true);
@@ -347,6 +349,7 @@ BlockBackend *blk_new(uint64_t perm, uint64_t shared_perm)
 
 /*
  * Creates a new BlockBackend, opens a new BlockDriverState, and connects both.
+ * The new BlockBackend is in the main AioContext.
  *
  * Just as with bdrv_open(), after having called this function the reference to
  * @options belongs to the block layer (even on failure).
@@ -382,7 +385,7 @@ BlockBackend *blk_new_open(const char *filename, const char *reference,
         perm |= BLK_PERM_RESIZE;
     }
 
-    blk = blk_new(perm, BLK_PERM_ALL);
+    blk = blk_new(qemu_get_aio_context(), perm, BLK_PERM_ALL);
     bs = bdrv_open(filename, reference, options, flags, errp);
     if (!bs) {
         blk_unref(blk);
@@ -1856,7 +1859,15 @@ void blk_op_unblock_all(BlockBackend *blk, Error *reason)
 
 AioContext *blk_get_aio_context(BlockBackend *blk)
 {
-    return bdrv_get_aio_context(blk_bs(blk));
+    BlockDriverState *bs = blk_bs(blk);
+
+    /* FIXME The AioContext of bs and blk can be inconsistent. For the moment,
+     * we prefer the one of bs for compatibility. */
+    if (bs) {
+        return bdrv_get_aio_context(blk_bs(blk));
+    }
+
+    return blk->ctx;
 }
 
 static AioContext *blk_aiocb_get_aio_context(BlockAIOCB *acb)
@@ -1888,6 +1899,7 @@ static int blk_do_set_aio_context(BlockBackend *blk, AioContext *new_context,
         }
     }
 
+    blk->ctx = new_context;
     return 0;
 }