Re: [libvirt] [PATCH v8 7/7] block: Enable qemu_open/close to work with fd sets

When qemu_open is passed a filename of the "/dev/fdset/nnn" format (where nnn is the fdset ID), an fd with matching access mode flags will be searched for within the specified monitor fd set. If the fd is found, a dup of the fd will be returned from qemu_open. Each fd set has a reference count. The purpose of the reference count is to determine if an fd set contains file descriptors that have open dup() references that have not yet been closed. It is incremented on qemu_open and decremented on qemu_close. It is not until the refcount is zero that file desriptors in an fd set can be closed. If an fd set has dup() references open, then we must keep the other fds in the fd set open in case a reopen of the file occurs that requires an fd with a different access mode. Signed-off-by: Corey Bryant <coreyb(a)linux.vnet.ibm.com&gt;

@@ -78,6 +79,69 @@ int qemu_madvise(void *addr, size_t len, int advice) #endif } +/* + * Dups an fd and sets the flags + */ +static int qemu_dup(int fd, int flags)

+{ + int ret; + int serrno; + int dup_flags; + int setfl_flags; + + if (flags & O_CLOEXEC) { +#ifdef F_DUPFD_CLOEXEC + ret = fcntl(fd, F_DUPFD_CLOEXEC, 0); +#else + ret = dup(fd); + if (ret != -1) { + qemu_set_cloexec(ret); + } +#endif + } else { + ret = dup(fd); + }