Am 05.03.2014 um 16:33 hat Benoît Canet geschrieben: > The Wednesday 05 Mar 2014 à 16:00:48 (+0100), Kevin Wolf wrote : > > The current iscsi block driver code makes the rather arbitrary decision > > that TYPE_MEDIUM_CHANGER and TYPE_TAPE devices have bs->sg = 1 and all > > other device types are disks. > > > > Instead of this, check for TYPE_DISK to expose the disk interface and > > make everything else bs->sg = 1. In particular, this includes devices > > with TYPE_STORAGE_ARRAY, which is what LUN 0 of an iscsi target is. > > (See https://bugzilla.redhat.com/show_bug.cgi?id=1067784 for the exact > > scenario.) > > > > Signed-off-by: Kevin Wolf <kw...@redhat.com> > > --- > > block/iscsi.c | 9 ++++----- > > 1 file changed, 4 insertions(+), 5 deletions(-) > > > > diff --git a/block/iscsi.c b/block/iscsi.c > > index 0a15f53..b490e98 100644 > > --- a/block/iscsi.c > > +++ b/block/iscsi.c > > @@ -1231,12 +1231,11 @@ static int iscsi_open(BlockDriverState *bs, QDict > > *options, int flags, > > bs->total_sectors = sector_lun2qemu(iscsilun->num_blocks, iscsilun); > > bs->request_alignment = iscsilun->block_size; > > > > - /* Medium changer or tape. We dont have any emulation for this so this > > must > > - * be sg ioctl compatible. We force it to be sg, otherwise qemu will > > try > > - * to read from the device to guess the image format. > > + /* We don't have any emulation for devices other than disks and > > CD-ROMs, so > > + * this must be sg ioctl compatible. We force it to be sg, otherwise > > qemu > > + * will try to read from the device to guess the image format. > > */ > > - if (iscsilun->type == TYPE_MEDIUM_CHANGER || > > - iscsilun->type == TYPE_TAPE) { > > + if (iscsilun->type != TYPE_DISK && iscsilun->type != TYPE_ROM) { > I don't understand you are talking about type TYPE_STORAGE_ARRAY in the commit > message but testing against TYPE_ROM and they are not the same. > Maybe a comment explaining the role of TYPE_ROM would give a clue to non scsi > savy persons like me.
TYPE_STORAGE_ARRAY is what exposed the bug (see the Bugzilla reference). It was previously bs->sg = 0, but becomes now bs->sg = 1. The reason for this is that the usual block layer operations only work on disks (i.e. hard disks = TYPE_DISK and CD-ROM drives = TYPE_ROM), so for all the rest we can only expose a generic SCSI device, but no real block device. Kevin
