Am 26.08.2015 um 17:31 schrieb Jeff Cody: > On Mon, Aug 24, 2015 at 10:13:16PM +0200, Max Reitz wrote: >> On 24.08.2015 21:34, Peter Lieven wrote: >>> Am 24.08.2015 um 20:39 schrieb Max Reitz: >>>> On 24.08.2015 10:06, Peter Lieven wrote: >>>>> If the file is readonly its not expected to grow so >>>>> save the blocking call to nfs_fstat_async and use >>>>> the value saved at connection time. Also important >>>>> the monitor (and thus the main loop) will not hang >>>>> if block device info is queried and the NFS share >>>>> is unresponsive. >>>>> >>>>> Signed-off-by: Peter Lieven <p...@kamp.de> >>>>> --- >>>>> v1->v2: update cache on reopen_prepare [Max] >>>>> >>>>> block/nfs.c | 35 +++++++++++++++++++++++++++++++++++ >>>>> 1 file changed, 35 insertions(+) >>>> Reviewed-by: Max Reitz <mre...@redhat.com> >>>> >>>> I hope you're ready for the "Stale actual-size value with >>>> cache=direct,read-only=on,format=raw files on NFS" reports. :-) >>> actually a good point, maybe the cache should only be used if >>> >>> !(bs->open_flags & BDRV_O_NOCACHE) >> Good enough a point to fix it? ;-) >> >> Max >> > It seems more inline with expected behavior, to add the cache checking > in before using the size cache. Would you be opposed to a v3 with > this check added in?
Of course, will send it tomorrow. > > One other concern I have is similar to a concern Max raised earlier - > about an external program modifying the raw image, while QEMU has it > opened r/o. In particular, I wonder about an NFS server making an > image either sparse / non-sparse. If it was exported read-only, it > may be a valid assumption that this could be done safely, as it would > not change the reported file size or contents, just the allocated size > on disk. This might be a use case. But if I allow caching the allocated filesize might not always be correct. This is even the case on a NFS share mounted through the kernel where some attributes a cached for some time. Anyway, would it hurt here if the actual filesize was too small? In fact it was incorrect since libnfs support was added :-) Peter
