Re: [Qemu-devel] [PATCH V3 0/6] ide: avoid main-loop hang on CDROM/NFS failure
On Fri, 11/06 09:42, Peter Lieven wrote: > This series aims at avoiding a hanging main-loop if a vserver has a > CDROM image mounted from a NFS share and that NFS share goes down. > Typical situation is that users mount an CDROM ISO to install something > and then forget to eject that CDROM afterwards. > As a consequence this mounted CD is able to bring down the > whole vserver if the backend NFS share is unreachable. This is bad > especially if the CDROM itself is not needed anymore at this point. If a storage backend is lost, would QEMU hang on guest reboot with this patch? If so, just for understanding the problem, what is the use case this series addresses? The code looks good to me apart from the two questions I left, and that I didn't fully understand the elementary transfer part. Thanks, Fam
Re: [Qemu-devel] [PATCH V3 0/6] ide: avoid main-loop hang on CDROM/NFS failure
Am 12.11.2015 um 12:33 schrieb Fam Zheng: On Fri, 11/06 09:42, Peter Lieven wrote: This series aims at avoiding a hanging main-loop if a vserver has a CDROM image mounted from a NFS share and that NFS share goes down. Typical situation is that users mount an CDROM ISO to install something and then forget to eject that CDROM afterwards. As a consequence this mounted CD is able to bring down the whole vserver if the backend NFS share is unreachable. This is bad especially if the CDROM itself is not needed anymore at this point. If a storage backend is lost, would QEMU hang on guest reboot with this patch? If so, just for understanding the problem, what is the use case this series addresses? Qemu would hang whenever the next request to the CDROM is made. This usually happens as soon as the CDROM is mounted (at least in Windows guests) even if there is no CDROM activity intiated by the user. This brings down every guest where the user just forgot to unmount the CDROM just because some NFS storage is unreachable. The code looks good to me apart from the two questions I left, and that I didn't fully understand the elementary transfer part. That indeed is not obvious. There was a long discussion on that topic in V1 of this series. Thanks, Peter
[Qemu-devel] [PATCH V3 0/6] ide: avoid main-loop hang on CDROM/NFS failure
This series aims at avoiding a hanging main-loop if a vserver has a CDROM image mounted from a NFS share and that NFS share goes down. Typical situation is that users mount an CDROM ISO to install something and then forget to eject that CDROM afterwards. As a consequence this mounted CD is able to bring down the whole vserver if the backend NFS share is unreachable. This is bad especially if the CDROM itself is not needed anymore at this point. v2->v3: - adressed Stefans comments on Patch 1 - added patches 2,4,5,6 - avoided the term cancel in Patch 3. Added an iovec, added a BH [Stefan] v1->v2: - fix offset for 2352 byte sector size [Kevin] - use a sync request if we continue an elementary transfer. As John pointed out we enter a race condition between next IDE command and async transfer otherwise. This is sill not optimal, but it fixes the NFS down problems for all cases where the NFS server goes down while there is no PIO CD activity. Of course, it could still happen during a PIO transfer, but I expect this to be the unlikelier case. I spent some effort trying to read more sectors at once and avoiding continuation of elementary transfers, but with whatever I came up it was destroying migration between different Qemu versions. I have a quite hackish patch that works and should survive migration, but I am not happy with it. So I would like to start with this version as it is a big improvement already. - Dropped Patch 5 because it is upstream meanwhile. Peter Lieven (6): ide/atapi: make PIO read requests async block: add blk_abort_aio_request ide: add support for IDEBufferedRequest ide: orphan all buffered requests on DMA cancel ide: enable buffered requests for ATAPI devices ide: enable buffered requests for PIO read requests block/block-backend.c | 17 +++ hw/ide/atapi.c | 103 +++-- hw/ide/core.c | 50 +++- hw/ide/internal.h | 14 ++ hw/ide/pci.c | 19 include/sysemu/block-backend.h | 3 ++ 6 files changed, 181 insertions(+), 25 deletions(-) -- 1.9.1
