Re: [Xen-devel] Failed to read /local/domain/0/backend/qdisk/26/51713/feature-flush-cache.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2013-10-29 at 12:02 +0800, ææå wrote:
> backend at /local/domain/0/backend/qdisk/26/51713
> Failed to
> read /local/domain/0/backend/qdisk/26/51713/feature-flush-cache. 

feature-* nodes are supposed to be optional and it appears that
qemu-xen-traditional's qdisk does not implement it. This particular node
indicates support for BLKIF_OP_FLUSH_DISKCACHE.

extras/mini-os/blkfront.c should deal with this. However it
unconditionally uses BLKIF_OP_FLUSH_DISKCACHE in blkfront_sync, I'm not
sure what the fallback (if any) is supposed to be. I doubt it can be
safely ignored, but that might be the only/best option?

qemu-xen (the upstream qemu) does seem to implement this feature, FWIW.

Ian.


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