From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36259) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZXWdK-0005Kj-GZ for qemu-devel@nongnu.org; Thu, 03 Sep 2015 11:41:03 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZXWdF-000858-D8 for qemu-devel@nongnu.org; Thu, 03 Sep 2015 11:41:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39795) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZXWdE-00084k-TH for qemu-devel@nongnu.org; Thu, 03 Sep 2015 11:40:57 -0400 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) by mx1.redhat.com (Postfix) with ESMTPS id 98E90B0CE1 for ; Thu, 3 Sep 2015 15:40:56 +0000 (UTC) From: "Daniel P. Berrange" Date: Thu, 3 Sep 2015 16:39:15 +0100 Message-Id: <1441294768-8712-34-git-send-email-berrange@redhat.com> In-Reply-To: <1441294768-8712-1-git-send-email-berrange@redhat.com> References: <1441294768-8712-1-git-send-email-berrange@redhat.com> Subject: [Qemu-devel] [PATCH FYI 33/46] migration: ensure qemu_fflush() always writes full data amount List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Juan Quintela , "Dr. David Alan Gilbert" , Gerd Hoffmann , Amit Shah , Paolo Bonzini 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 f9242e8..a4e5468 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 int (QEMUFilePutBufferFunc)(void *opaque, const uint8_t *buf, int64_t pos, int 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 d1d2c17..9f42f5c 100644 --- a/migration/qemu-file.c +++ b/migration/qemu-file.c @@ -123,11 +123,13 @@ 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; @@ -135,21 +137,27 @@ 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); } + f->buf_index = 0; + f->iovcnt = 0; } void ram_control_before_iterate(QEMUFile *f, uint64_t flags) -- 2.4.3