block: Clean up remaining users of "removable"

BlockDriverState member removable is a confused mess.  It is true when
an ide-cd, scsi-cd or floppy qdev is attached, or when the
BlockDriverState was created with -drive if={floppy,sd} or -drive
if={ide,scsi,xen,none},media=cdrom ("created removable"), except when
an ide-hd, scsi-hd, scsi-generic or virtio-blk qdev is attached.

Three users remain:

1. eject_device(), via bdrv_is_removable() uses it to determine
   whether a block device can eject media.

2. bdrv_info() is monitor command "info block".  QMP documentation
   says "true if the device is removable, false otherwise".  From the
   monitor user's point of view, the only sensible interpretation of
   "is removable" is "can eject media with monitor commands eject and
   change".

A block device can eject media unless a device is attached that
doesn't support it.  Switch the two users over to new
bdrv_dev_has_removable_media() that returns exactly that.

3. bdrv_getlength() uses to suppress its length cache when media can
   change (see commit 46a4e4e6).  Media change is either monitor
   command change (updates the length cache), monitor command eject
   (doesn't update the length cache, easily fixable), or physical
   media change (invalidates length cache, not so easily fixable).

I'm refraining from improving anything here, because this series is
long enough already.  Instead, I simply switch it over to
bdrv_dev_has_removable_media() as well.

This changes the behavior of the length cache and of monitor commands
eject and change in two cases:

a. drive not created removable, no device attached

   The commit makes the drive removable, and defeats the length cache.

   Example: -drive if=none

b. drive created removable, but the attached drive is non-removable,
   and doesn't call bdrv_set_removable(..., 0) (most devices don't)

   The commit makes the drive non-removable, and enables the length
   cache.

   Example: -drive if=xen,media=cdrom -M xenpv

   The other non-removable devices that don't call
   bdrv_set_removable() can't currently use a drive created removable,
   either because they aren't qdevified, or because they lack a drive
   property.  Won't stay that way.

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

4 files changed, 19 insertions, 9 deletions

diff --git a/block.c b/block.c
index 7225b15bdf..fee45bfbf4 100644
--- a/block.c
+++ b/block.c
@@ -802,6 +802,9 @@ void bdrv_set_dev_ops(BlockDriverState *bs, const BlockDevOps *ops,
 {
     bs->dev_ops = ops;
     bs->dev_opaque = opaque;
+    if (bdrv_dev_has_removable_media(bs) && bs == bs_snapshots) {
+        bs_snapshots = NULL;
+    }
 }
 
 static void bdrv_dev_change_media_cb(BlockDriverState *bs)
@@ -811,6 +814,11 @@ static void bdrv_dev_change_media_cb(BlockDriverState *bs)
     }
 }
 
+bool bdrv_dev_has_removable_media(BlockDriverState *bs)
+{
+    return !bs->dev || (bs->dev_ops && bs->dev_ops->change_media_cb);
+}
+
 static void bdrv_dev_resize_cb(BlockDriverState *bs)
 {
     if (bs->dev_ops && bs->dev_ops->resize_cb) {
@@ -1329,7 +1337,7 @@ int64_t bdrv_getlength(BlockDriverState *bs)
     if (!drv)
         return -ENOMEDIUM;
 
-    if (bs->growable || bs->removable) {
+    if (bs->growable || bdrv_dev_has_removable_media(bs)) {
         if (drv->bdrv_getlength) {
             return drv->bdrv_getlength(bs);
         }
@@ -1614,11 +1622,6 @@ void bdrv_set_removable(BlockDriverState *bs, int removable)
     }
 }
 
-int bdrv_is_removable(BlockDriverState *bs)
-{
-    return bs->removable;
-}
-
 int bdrv_is_read_only(BlockDriverState *bs)
 {
     return bs->read_only;
@@ -1897,7 +1900,8 @@ void bdrv_info(Monitor *mon, QObject **ret_data)
 
         bs_obj = qobject_from_jsonf("{ 'device': %s, 'type': 'unknown', "
                                     "'removable': %i, 'locked': %i }",
-                                    bs->device_name, bs->removable,
+                                    bs->device_name,
+                                    bdrv_dev_has_removable_media(bs),
                                     bdrv_dev_is_medium_locked(bs));
 
         if (bs->drv) {
diff --git a/block.h b/block.h
index 4691090c8a..860e30d14f 100644
--- a/block.h
+++ b/block.h
@@ -34,6 +34,7 @@ typedef struct BlockDevOps {
      * Runs when virtual media changed (monitor commands eject, change)
      * Beware: doesn't run when a host device's physical media
      * changes.  Sure would be useful if it did.
+     * Device models with removable media must implement this callback.
      */
     void (*change_media_cb)(void *opaque);
     /*
@@ -99,6 +100,7 @@ void bdrv_detach_dev(BlockDriverState *bs, void *dev);
 void *bdrv_get_attached_dev(BlockDriverState *bs);
 void bdrv_set_dev_ops(BlockDriverState *bs, const BlockDevOps *ops,
                       void *opaque);
+bool bdrv_dev_has_removable_media(BlockDriverState *bs);
 bool bdrv_dev_is_medium_locked(BlockDriverState *bs);
 int bdrv_read(BlockDriverState *bs, int64_t sector_num,
               uint8_t *buf, int nb_sectors);
@@ -206,7 +208,6 @@ void bdrv_set_on_error(BlockDriverState *bs, BlockErrorAction on_read_error,
                        BlockErrorAction on_write_error);
 BlockErrorAction bdrv_get_on_error(BlockDriverState *bs, int is_read);
 void bdrv_set_removable(BlockDriverState *bs, int removable);
-int bdrv_is_removable(BlockDriverState *bs);
 int bdrv_is_read_only(BlockDriverState *bs);
 int bdrv_is_sg(BlockDriverState *bs);
 int bdrv_enable_write_cache(BlockDriverState *bs);
diff --git a/blockdev.c b/blockdev.c
index 3f00b2e61b..ddf1f8fb7b 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -636,7 +636,7 @@ out:
 
 static int eject_device(Monitor *mon, BlockDriverState *bs, int force)
 {
-    if (!bdrv_is_removable(bs)) {
+    if (!bdrv_dev_has_removable_media(bs)) {
         qerror_report(QERR_DEVICE_NOT_REMOVABLE, bdrv_get_device_name(bs));
         return -1;
     }
diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
index 1a49217e33..d6e838cdce 100644
--- a/hw/scsi-disk.c
+++ b/hw/scsi-disk.c
@@ -1172,12 +1172,17 @@ static void scsi_destroy(SCSIDevice *dev)
     blockdev_mark_auto_del(s->qdev.conf.bs);
 }
 
+static void scsi_cd_change_media_cb(void *opaque)
+{
+}
+
 static bool scsi_cd_is_medium_locked(void *opaque)
 {
     return ((SCSIDiskState *)opaque)->tray_locked;
 }
 
 static const BlockDevOps scsi_cd_block_ops = {
+    .change_media_cb = scsi_cd_change_media_cb,
     .is_medium_locked = scsi_cd_is_medium_locked,
 };