From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49124) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aQxXI-0006Qw-0A for qemu-devel@nongnu.org; Wed, 03 Feb 2016 08:32:02 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aQxXD-0001OE-5Q for qemu-devel@nongnu.org; Wed, 03 Feb 2016 08:31:55 -0500 Received: from mx1.redhat.com ([209.132.183.28]:60849) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aQxXC-0001O9-TQ for qemu-devel@nongnu.org; Wed, 03 Feb 2016 08:31:51 -0500 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (Postfix) with ESMTPS id 58CC6E1B77 for ; Wed, 3 Feb 2016 13:31:50 +0000 (UTC) Date: Wed, 3 Feb 2016 13:31:46 +0000 From: "Daniel P. Berrange" Message-ID: <20160203133146.GL30222@redhat.com> References: <1452599056-27357-1-git-send-email-berrange@redhat.com> <1452599056-27357-4-git-send-email-berrange@redhat.com> <20160128175346.GC2911@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20160128175346.GC2911@work-vm> Subject: Re: [Qemu-devel] [PATCH v1 03/22] migration: ensure qemu_fflush() always writes full data amount Reply-To: "Daniel P. Berrange" List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" Cc: Amit Shah , qemu-devel@nongnu.org, Juan Quintela On Thu, Jan 28, 2016 at 05:53:46PM +0000, Dr. David Alan Gilbert wrote: > * Daniel P. Berrange (berrange@redhat.com) wrote: > > The QEMUFile writev_buffer / put_buffer functions are expected > > to write out the full set of requested data, blocking until > > complete. The qemu_fflush() caller does not expect to deal with > > partial writes. Clarify the function comments and add a sanity > > check to the code to catch mistaken implementations. > > > > Signed-off-by: Daniel P. Berrange > > --- > > include/migration/qemu-file.h | 6 ++++-- > > migration/qemu-file.c | 16 ++++++++++++---- > > 2 files changed, 16 insertions(+), 6 deletions(-) > > > > diff --git a/include/migration/qemu-file.h b/include/migration/qemu-file.h > > index b5d08d2..5debe8c 100644 > > --- a/include/migration/qemu-file.h > > +++ b/include/migration/qemu-file.h > > @@ -29,7 +29,8 @@ > > > > /* This function writes a chunk of data to a file at the given position. > > * The pos argument can be ignored if the file is only being used for > > - * streaming. The handler should try to write all of the data it can. > > + * streaming. The handler must write all of the data or return a negative > > + * errno value. > > */ > > typedef ssize_t (QEMUFilePutBufferFunc)(void *opaque, const uint8_t *buf, > > int64_t pos, size_t size); > > @@ -55,7 +56,8 @@ typedef int (QEMUFileCloseFunc)(void *opaque); > > typedef int (QEMUFileGetFD)(void *opaque); > > > > /* > > - * This function writes an iovec to file. > > + * This function writes an iovec to file. The handler must write all > > + * of the data or return a negative errno value. > > */ > > typedef ssize_t (QEMUFileWritevBufferFunc)(void *opaque, struct iovec *iov, > > int iovcnt, int64_t pos); > > diff --git a/migration/qemu-file.c b/migration/qemu-file.c > > index 0bbd257..f89e64e 100644 > > --- a/migration/qemu-file.c > > +++ b/migration/qemu-file.c > > @@ -107,11 +107,13 @@ bool qemu_file_is_writable(QEMUFile *f) > > * Flushes QEMUFile buffer > > * > > * If there is writev_buffer QEMUFileOps it uses it otherwise uses > > - * put_buffer ops. > > + * put_buffer ops. This will flush all pending data. If data was > > + * only partially flushed, it will set an error state. > > */ > > void qemu_fflush(QEMUFile *f) > > { > > ssize_t ret = 0; > > + ssize_t expect = 0; > > > > if (!qemu_file_is_writable(f)) { > > return; > > @@ -119,21 +121,27 @@ void qemu_fflush(QEMUFile *f) > > > > if (f->ops->writev_buffer) { > > if (f->iovcnt > 0) { > > + expect = iov_size(f->iov, f->iovcnt); > > ret = f->ops->writev_buffer(f->opaque, f->iov, f->iovcnt, f->pos); > > } > > } else { > > if (f->buf_index > 0) { > > + expect = f->buf_index; > > ret = f->ops->put_buffer(f->opaque, f->buf, f->pos, f->buf_index); > > } > > } > > + > > if (ret >= 0) { > > f->pos += ret; > > } > > - f->buf_index = 0; > > - f->iovcnt = 0; > > - if (ret < 0) { > > + /* We expect the QEMUFile write impl to send the full > > + * data set we requested, so sanity check that. > > + */ > > + if (ret < 0 || ret != expect) { > > qemu_file_set_error(f, ret); > > You could simplify that to if (ret != expect) couldn't you? > > In the case you're trying to guard against, the value past > to qemu_file_set_error is potentially truncated; which in the worst > case could make it appear as success; although I doubt that > can happen in our uses. qemu_file_set_error expects an errni, so in fact my code was buggy if the ret != expect part got evaluated, so I'll change this to if (ret != expect) { qemu_file_set_error(f, ret < 0 ? ret : -EIO); } > > Reviewed-by: Dr. David Alan Gilbert Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|