From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55632) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ceqR2-0003Wu-Ni for qemu-devel@nongnu.org; Fri, 17 Feb 2017 16:51:25 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ceqR2-0006cy-0E for qemu-devel@nongnu.org; Fri, 17 Feb 2017 16:51:24 -0500 Date: Fri, 17 Feb 2017 16:51:17 -0500 From: Jeff Cody Message-ID: <20170217215117.GM19045@localhost.localdomain> References: <1487349541-10201-1-git-send-email-pl@kamp.de> <1487349541-10201-3-git-send-email-pl@kamp.de> <20170217213715.GJ19045@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [PATCH 2/2] block/nfs: try to avoid the bounce buffer in pwritev List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: Peter Lieven , kwolf@redhat.com, qemu-devel@nongnu.org, qemu-block@nongnu.org, mreitz@redhat.com On Fri, Feb 17, 2017 at 03:42:52PM -0600, Eric Blake wrote: > On 02/17/2017 03:37 PM, Jeff Cody wrote: > > On Fri, Feb 17, 2017 at 05:39:01PM +0100, Peter Lieven wrote: > >> if the passed qiov contains exactly one iov we can > >> pass the buffer directly. > >> > >> Signed-off-by: Peter Lieven > >> --- > >> block/nfs.c | 23 ++++++++++++++++------- > >> 1 file changed, 16 insertions(+), 7 deletions(-) > >> > >> diff --git a/block/nfs.c b/block/nfs.c > >> index ab5dcc2..bb4b75f 100644 > >> --- a/block/nfs.c > >> +++ b/block/nfs.c > >> @@ -295,20 +295,27 @@ static int coroutine_fn nfs_co_pwritev(BlockDriverState *bs, uint64_t offset, > >> NFSClient *client = bs->opaque; > >> NFSRPC task; > >> char *buf = NULL; > >> + bool my_buffer = false; > > > > g_free() is a nop if buf is NULL, so there is no need for the my_buffer > > variable & check. > > Umm, yes there is: > > >> + if (iov->niov != 1) { > >> + buf = g_try_malloc(bytes); > >> + if (bytes && buf == NULL) { > >> + return -ENOMEM; > >> + } > >> + qemu_iovec_to_buf(iov, 0, buf, bytes); > >> + my_buffer = true; > >> + } else { > >> + buf = iov->iov[0].iov_base; > > If we took the else branch, then we definitely do not want to be calling > g_free(buf). Doh! > > >> } > >> > >> - qemu_iovec_to_buf(iov, 0, buf, bytes); > >> - > >> if (nfs_pwrite_async(client->context, client->fh, > >> offset, bytes, buf, > >> nfs_co_generic_cb, &task) != 0) { > >> - g_free(buf); > >> + if (my_buffer) { > >> + g_free(buf); > >> + } > > It looks correct as-is to me. Indeed. Reviewed-by: Jeff Cody