On Wed, Sep 20, 2017 at 04:35:58PM +0300, Nikolay Shirokovskiy wrote: > > > On 20.09.2017 16:30, Daniel P. Berrange wrote: > > On Wed, Sep 20, 2017 at 02:58:55PM +0300, Nikolay Shirokovskiy wrote: > >> saferead is not suitable for direct reads. If file size is not multiple > >> of align size then we get EINVAL on the read(2) that is supposed to > >> return 0 because read buffer will not be aligned at this point. > >> > >> Let's not read again after partial read and check that we read > >> everything by comparing the number of total bytes read against file size. > > > > What scenario did you actually hit this problem in ? IIUC, we should > > only be using O_DIRECT against block devices or plain files, and in both > > those cases we should never see short-read unless we hit EOF. > > Yes. But saferead is generic function and rereads file after short read. > Here we got EINVAL because of misalignement. I understand that, but how have you actually hit this in the real world. AFAICT, the short-read and subsequent problem with misalignemt should be impossible to hit, because any files we use O_DIRECT on should not ever return a shortread. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
