On 06/14/2012 09:55 AM, Corey Bryant wrote: > This patch series adds the pass-fd QMP monitor command, which allows > an fd to be passed via SCM_RIGHTS, and returns the received file > descriptor. Support is also added to the block layer to allow QEMU > to dup the fd when the filename is of the /dev/fd/X format. This > is useful if MAC policy prevents QEMU from opening specific types > of files. Something to think about on how this will interact with Jeff's work on block-commit. That is an interface where qemu must reopen backing files which were previously O_RDONLY to now be O_RDWR. By default (when open() is supported in qemu, and qemu is using the actual file name), this means 'block-commit' works without needing any fd names. But with this new fd-passing approach, a file originally opened as O_RDONLY /dev/fd/21 will need to be reopened, but the reopened fd will (likely) not be 21. In other words, we need to make sure 'block-commit' supports the ability to pass in optional arguments that specify the file name of the backing file to be reopened, so that libvirt can pass in O_RDWR fds to replace the existing O_RDONLY fd, and be aware that the /dev/fd/nn naming of the reopen will be different. -- Eric Blake eblake@xxxxxxxxxx +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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