On 06/14/2016 09:19 AM, Max Reitz wrote: > On 10.06.2016 23:59, John Snow wrote: >> If a device still has an attached BDS because the medium has not yet >> been removed, we will be unable to migrate to a new host because >> blk_flush will return an error for that backend. >> >> Replace the call to blk_is_available to blk_is_inserted to weaken >> the check and allow flushes from the backend to work, while still >> disallowing flushes from the frontend/device model to work. >> >> This fixes a regression present in 2.6.0 caused by the following commit: >> fe1a9cbc339bb54d20f1ca4c1e8788d16944d5cf >> block: Move some bdrv_*_all() functions to BB >> >> Signed-off-by: John Snow <js...@redhat.com> >> --- >> block/block-backend.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) > > I'm still not sure we shouldn't do the same for blk_{co,aio}_flush(). I > guess you exclude them here because you specifically want to fix the > issue mentioned in the commit message, but then we could just make > blk_flush_all() ignore an -ENOMEDIUM.
Yeah, I didn't investigate the full path. Just making the minimal fixes. Is there a concern that this may still leave certain pathways broken when the CDROM tray is open? I don't know of any immediately without digging again. > > I personally think we should make all blk_*flush() functions use > blk_is_inserted() instead of blk_is_available(). As we have discussed on > IRC, there are probably not that many cases a guest can flush a medium > in an open tray anyway (because the main use case are read-only > CD-ROMs), and even if so, that wouldn't change any data, so even if the > guest can actually flush something on an open tray, I don't think anyone > would complain. > > Max > I have difficulty making pragmatic arguments when purity is at stake, but I've already wandered outside of my device model, so I will defer to your judgment. >> diff --git a/block/block-backend.c b/block/block-backend.c >> index 34500e6..d1e875e 100644 >> --- a/block/block-backend.c >> +++ b/block/block-backend.c >> @@ -1122,7 +1122,7 @@ int blk_co_flush(BlockBackend *blk) >> >> int blk_flush(BlockBackend *blk) >> { >> - if (!blk_is_available(blk)) { >> + if (!blk_is_inserted(blk)) { >> return -ENOMEDIUM; >> } >> >> > > Is this a NACK unless I attempt to address the wider design issue?