Am 04.08.2017 um 03:49 hat Eric Blake geschrieben: > On 08/03/2017 10:21 AM, Eric Blake wrote: > > On 08/03/2017 10:02 AM, Kevin Wolf wrote: > >> BDRV_O_ALLOW_RDWR is a flag that tells whether qemu can internally > >> reopen a node read-write temporarily because the user requested > >> read-write for the top-level image, but qemu decided that read-only is > >> enough for this node (a backing file). > >> > >> bdrv_reopen() is different, it is also used for cases where the user > >> changed their mind and wants to update the options. There is no reason > >> to forbid making a node read-write in that case. > > > > Hmm, I wonder. https://bugzilla.redhat.com/show_bug.cgi?id=1465320 > > details a failure when starting qemu with a read-write NBD disk, then > > taking several snapshots (nbd <- snap1 <- snap2 <- snap3), then where > > intermediate commit (snap2 into nbd) works but live commit (snap3 into > > nbd) fails with a message that nbd does not support reopening. I'm > > presuming that your series may help to address that; I'll give it a spin > > and see what happens. > > Nope, even with your patches, I'm still getting: > > {'execute':'block-commit','arguments':{'device':'drive-image1','top':'bar2'}} > {"return": {}} > {"timestamp": {"seconds": 1501811285, "microseconds": 439748}, "event": > "BLOCK_JOB_COMPLETED", "data": {"device": "drive-image1", "len": > 2097152, "offset": 2097152, "speed": 0, "type": "commit"}} > > {'execute':'block-commit','arguments':{'device':'drive-image1','top':'bar3'}} > {"error": {"class": "GenericError", "desc": "Block format 'nbd' used by > node '#block048' does not support reopening files"}}
That's simply NBD not implementing .bdrv_reopen_*. In other words, not a bug, but just a missing feature. Kevin
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