Daniel P. Berrange wrote:
On Fri, Aug 15, 2014 at 12:55:58PM +0400, Roman Bogorodskiy wrote:
Daniel P. Berrange wrote:
On Fri, Aug 15, 2014 at 12:44:21PM +0400, Roman Bogorodskiy wrote:
virStorageBackendVolDownloadLocal and virStorageBackendVolUploadLocal use virFDStreamOpenFile function to work with the volume fd.
virFDStreamOpenFile calls virFDStreamOpenFileInternal that implements handling of the non-blocking I/O. If a file is not a character device and not a fifo, it uses libvirt_iohelper.
On FreeBSD, it doesn't work as expected because disks are exposed as character devices.
Why does that cause a problem ? The reason we use iohelper is because POSIX does not have O_NONBLOCK work on plain files, so we need to use the iohelper so that we have a pipe we can set O_NONBLOCK on. If FreeBSD disks are character devices though, O_NONBLOCK should work fine on them avoiding the need for iohelper.
O_NONBLOCK doesn't work for some reason, at least on ZFS volumes: fcntl() fails with:
fcntl: Inappropriate ioctl for device
I have asked a question on an appropriate mailing list:
https://lists.freebsd.org/pipermail/freebsd-fs/2014-August/019923.html
I've also included a test program I use to reproduce that there.
Ah ok, so can you update the commit message to explicitly mention that ZFS character devices are unusual in not supporting O_NOBLOBKJ
I did some more checks and it looks like O_NONBLOCK is not supported not only on ZFS volumes, but on other disk drivers as well; I got the same result for SATA and memory disks. I'll update a commit message to say something like this:
On FreeBSD, it doesn't work as expected because disks are exposed as character devices and do not support O_NONBLOCK.
I'll wait for other comments to avoid resending the series just because of a commit message change. Roman Bogorodskiy