[Qemu-devel] [PATCH 3/3] block: remove legacy_dinfo at blk_detach_dev time

[Paolo Bonzini <pbonzini@redhat.com>]

Currently, blockdev_del_drive (and before it blk_auto_del) does a blk_unref
that will cause blk_delete to be called and the DriveInfo to be freed.
But really, we want to free the drive info as soon as the device is
detached, even if there are other references for whatever reason, so
that the QemuOpts are freed as well and the id can be reused.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/block-backend.c     | 13 +++++++++----
 blockdev.c                |  9 +++++----
 include/sysemu/blockdev.h |  1 +
 3 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/block/block-backend.c b/block/block-backend.c
index ebdf78a..0a85c6a 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -65,8 +65,6 @@ static const AIOCBInfo block_backend_aiocb_info = {
     .aiocb_size = sizeof(BlockBackendAIOCB),
 };
 
-static void drive_info_del(DriveInfo *dinfo);
-
 /* All the BlockBackends (except for hidden ones) */
 static QTAILQ_HEAD(, BlockBackend) blk_backends =
     QTAILQ_HEAD_INITIALIZER(blk_backends);
@@ -165,6 +163,7 @@ static void blk_delete(BlockBackend *blk)
 {
     assert(!blk->refcnt);
     assert(!blk->dev);
+    assert(!blk->legacy_dinfo);
     if (blk->bs) {
         blk_remove_bs(blk);
     }
@@ -179,19 +178,25 @@ static void blk_delete(BlockBackend *blk)
         QTAILQ_REMOVE(&blk_backends, blk, link);
     }
     g_free(blk->name);
-    drive_info_del(blk->legacy_dinfo);
     block_acct_cleanup(&blk->stats);
     g_free(blk);
 }
 
-static void drive_info_del(DriveInfo *dinfo)
+void blk_release_legacy_dinfo(BlockBackend *blk)
 {
+    DriveInfo *dinfo = blk->legacy_dinfo;
+
     if (!dinfo) {
         return;
     }
     qemu_opts_del(dinfo->opts);
     g_free(dinfo->serial);
     g_free(dinfo);
+    blk->legacy_dinfo = NULL;
+    /* We are not interested anymore in retrieving the BlockBackend
+     * via blk_by_legacy_dinfo, so let it die.
+     */
+    blk_unref(blk);
 }
 
 int blk_get_refcnt(BlockBackend *blk)
diff --git a/blockdev.c b/blockdev.c
index 2dfb2d8..85f0cb5 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -120,10 +120,10 @@ void override_max_devs(BlockInterfaceType type, int max_devs)
  */
 void blockdev_del_drive(BlockBackend *blk)
 {
-    DriveInfo *dinfo = blk_legacy_dinfo(blk);
     BlockDriverState *bs = blk_bs(blk);
     AioContext *aio_context;
 
+    blk_ref(blk);
     if (bs) {
         aio_context = bdrv_get_aio_context(bs);
         aio_context_acquire(aio_context);
@@ -135,9 +135,10 @@ void blockdev_del_drive(BlockBackend *blk)
         aio_context_release(aio_context);
     }
 
-    if (dinfo) {
-        blk_unref(blk);
+    if (blk_legacy_dinfo(blk)) {
+        blk_release_legacy_dinfo(blk);
     }
+    blk_unref(blk);
 }
 
 /**
@@ -2811,7 +2812,7 @@ void hmp_drive_del(Monitor *mon, const QDict *qdict)
         blk_set_on_error(blk, BLOCKDEV_ON_ERROR_REPORT,
                          BLOCKDEV_ON_ERROR_REPORT);
     } else {
-        blk_unref(blk);
+        blockdev_del_drive(blk);
     }
 
     aio_context_release(aio_context);
diff --git a/include/sysemu/blockdev.h b/include/sysemu/blockdev.h
index ae7ad67..5722b9f 100644
--- a/include/sysemu/blockdev.h
+++ b/include/sysemu/blockdev.h
@@ -44,6 +44,7 @@ struct DriveInfo {
 DriveInfo *blk_legacy_dinfo(BlockBackend *blk);
 DriveInfo *blk_set_legacy_dinfo(BlockBackend *blk, DriveInfo *dinfo);
 BlockBackend *blk_by_legacy_dinfo(DriveInfo *dinfo);
+void blk_release_legacy_dinfo(BlockBackend *blk);
 
 void override_max_devs(BlockInterfaceType type, int max_devs);
 
-- 
2.5.0