Re: [libvirt] [PATCH v3 3/5] osdep: Enable qemu_open to dup pre-opened fd

On 06/15/2012 01:19 PM, Corey Bryant wrote: >>> There are some flags that I don't think we'll be able to change. For >>> example: O_RDONLY, O_WRONLY, O_RDWR. I assume libvirt would open all >>> files O_RDWR. >> >> I think we need to check all of them and fail qemu_open() if they don't >> match. Those that qemu can change, should be just changed, of course. >> > > Ok. I remember a scenario where QEMU opens a file read-only (perhaps to > check headers and determine the file format) before re-opening it > read-write. Perhaps this is only when format= isn't specified with > -drive. I'm thinking we may need to change flags to read-write where > they used to be read-only, in some circumstances. In those situations, libvirt would pass fd with O_RDWR, and qemu_open() would be fine requesting O_RDONLY the first time (subset is okay), and O_RDWR the second time. Where you have to error out is where libvirt passes O_RDONLY but qemu wants O_RDWR, and so forth.