From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:45936) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SzsAG-0001DR-Aa for qemu-devel@nongnu.org; Fri, 10 Aug 2012 12:34:22 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1SzsAF-0002LR-0t for qemu-devel@nongnu.org; Fri, 10 Aug 2012 12:34:20 -0400 Received: from mx1.redhat.com ([209.132.183.28]:31379) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SzsAE-0002LB-NI for qemu-devel@nongnu.org; Fri, 10 Aug 2012 12:34:18 -0400 Message-ID: <502537FF.8020701@redhat.com> Date: Fri, 10 Aug 2012 18:34:07 +0200 From: Kevin Wolf MIME-Version: 1.0 References: <1344564649-6272-1-git-send-email-coreyb@linux.vnet.ibm.com> <1344564649-6272-8-git-send-email-coreyb@linux.vnet.ibm.com> In-Reply-To: <1344564649-6272-8-git-send-email-coreyb@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v8 7/7] block: Enable qemu_open/close to work with fd sets List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Corey Bryant Cc: aliguori@us.ibm.com, stefanha@linux.vnet.ibm.com, libvir-list@redhat.com, qemu-devel@nongnu.org, lcapitulino@redhat.com, pbonzini@redhat.com, eblake@redhat.com Am 10.08.2012 04:10, schrieb Corey Bryant: > 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 > @@ -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) qemu_dup() is probably not a good name. We'll want to use it when we need to get a wrapper around dup(). And I suspect that we will need it for making bdrv_reopen() compatible with fdset refcounting. > +{ > + 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); > + } qemu_open() is supposed to add O_CLOEXEC by itself, so I think we should execute the then branch unconditionally (or we would have to change the qemu_dup() call below to add it - but the fact that O_CLOEXEC isn't even necessarily defined doesn't help with that). Kevin