From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:51338) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RGAIY-0001Vl-3h for qemu-devel@nongnu.org; Tue, 18 Oct 2011 10:05:47 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RGAIR-0003CL-S0 for qemu-devel@nongnu.org; Tue, 18 Oct 2011 10:05:41 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39836) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RGAIR-0003C2-Eo for qemu-devel@nongnu.org; Tue, 18 Oct 2011 10:05:35 -0400 Date: Tue, 18 Oct 2011 12:03:51 -0200 From: Marcelo Tosatti Message-ID: <20111018140351.GC21122@amt.cnet> References: <1318866452-30026-1-git-send-email-stefanha@linux.vnet.ibm.com> <1318866452-30026-6-git-send-email-stefanha@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1318866452-30026-6-git-send-email-stefanha@linux.vnet.ibm.com> Subject: Re: [Qemu-devel] [RFC 5/6] block: core copy-on-read logic List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: Kevin Wolf , Paolo Bonzini , qemu-devel@nongnu.org On Mon, Oct 17, 2011 at 04:47:31PM +0100, Stefan Hajnoczi wrote: > Signed-off-by: Stefan Hajnoczi > --- > block.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > trace-events | 1 + > 2 files changed, 70 insertions(+), 0 deletions(-) > > diff --git a/block.c b/block.c > index 0c22741..2aec6b4 100644 > --- a/block.c > +++ b/block.c > @@ -1409,6 +1409,55 @@ int bdrv_pwrite_sync(BlockDriverState *bs, int64_t offset, > return 0; > } > > +static int coroutine_fn bdrv_co_copy_on_readv(BlockDriverState *bs, > + int64_t sector_num, int nb_sectors, QEMUIOVector *qiov) > +{ > + void *bounce_buffer; > + struct iovec iov; > + QEMUIOVector bounce_qiov; > + int64_t cluster_sector_num; > + int cluster_nb_sectors; > + size_t skip_bytes; > + int ret; > + > + /* Cover entire cluster so no additional backing file I/O is required when > + * allocating cluster in the image file. > + */ > + round_to_clusters(bs, sector_num, nb_sectors, > + &cluster_sector_num, &cluster_nb_sectors); > + > + trace_bdrv_co_copy_on_readv(bs, sector_num, nb_sectors, > + cluster_sector_num, cluster_nb_sectors); > + > + iov.iov_len = cluster_nb_sectors * BDRV_SECTOR_SIZE; > + iov.iov_base = bounce_buffer = qemu_blockalign(bs, iov.iov_len); > + qemu_iovec_init_external(&bounce_qiov, &iov, 1); > + > + ret = bs->drv->bdrv_co_readv(bs, cluster_sector_num, cluster_nb_sectors, > + &bounce_qiov); > + if (ret < 0) { > + goto err; > + } > + > + ret = bs->drv->bdrv_co_writev(bs, cluster_sector_num, cluster_nb_sectors, > + &bounce_qiov); > + if (ret < 0) { > + /* It might be okay to ignore write errors for guest requests. If this > + * is a deliberate copy-on-read then we don't want to ignore the error. > + * Simply report it in all cases. > + */ > + goto err; > + } > + > + skip_bytes = (sector_num - cluster_sector_num) * BDRV_SECTOR_SIZE; > + qemu_iovec_from_buffer(qiov, bounce_buffer + skip_bytes, > + nb_sectors * BDRV_SECTOR_SIZE); > + > +err: > + qemu_vfree(bounce_buffer); > + return ret; > +} > + > /* > * Handle a read request in coroutine context > */ > @@ -1431,7 +1480,27 @@ static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs, > } > > req = tracked_request_add(bs, sector_num, nb_sectors, false); > + > + if (bs->copy_on_read) { > + int pnum; > + > + /* TODO it is not safe to call bdrv_is_allocated() in coroutine context > + * because it's a synchronous interface. We probably want a > + * bdrv_co_is_allocated(). */ > + ret = bdrv_is_allocated(bs, sector_num, nb_sectors, &pnum); > + if (ret < 0) { > + goto out; > + } This lacks shared base image support, BTW (as in copy should be performed only if cluster not in destination chain). Could be added later.