From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH 3/5] lguest: replace VIRTIO_F_BARRIER support with VIRTIO_F_FLUSH support Date: Thu, 19 Aug 2010 17:15:41 +0200 Message-ID: <4C6D4A9D.1020400@kernel.org> References: <1281977523-19335-1-git-send-email-tj@kernel.org> <1281977523-19335-4-git-send-email-tj@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: jaxboe@fusionio.com, linux-fsdevel@vger.kernel.org, linux-scsi@vger.kernel.org, linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, hch@lst.de, James.Bottomley@suse.de, tytso@mit.edu, chris.mason@oracle.com, swhiteho@redhat.com, konishi.ryusuke@lab.ntt.co.jp, dm-devel@redhat.com, vst@vlnb.net, jack@suse.cz, rwheeler@redhat.com, hare@suse.de, neilb@suse.de, rusty@rustcorp.com.au, mst@redhat.com, Tejun Heo To: Tejun Heo Return-path: In-Reply-To: <1281977523-19335-4-git-send-email-tj@kernel.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org VIRTIO_F_BARRIER is deprecated. Replace it with VIRTIO_F_FLUSH support. Signed-off-by: Tejun Heo Cc: Rusty Russell Cc: Christoph Hellwig --- FUA support dropped as suggested by Christoph. Rusty, can you please ack this version too? I tested it with the updated virtio_blk and it works fine. Thanks. Documentation/lguest/lguest.c | 29 +++++++++-------------------- 1 file changed, 9 insertions(+), 20 deletions(-) Index: block/Documentation/lguest/lguest.c =================================================================== --- block.orig/Documentation/lguest/lguest.c +++ block/Documentation/lguest/lguest.c @@ -1639,15 +1639,6 @@ static void blk_request(struct virtqueue off = out->sector * 512; /* - * The block device implements "barriers", where the Guest indicates - * that it wants all previous writes to occur before this write. We - * don't have a way of asking our kernel to do a barrier, so we just - * synchronize all the data in the file. Pretty poor, no? - */ - if (out->type & VIRTIO_BLK_T_BARRIER) - fdatasync(vblk->fd); - - /* * In general the virtio block driver is allowed to try SCSI commands. * It'd be nice if we supported eject, for example, but we don't. */ @@ -1679,6 +1670,13 @@ static void blk_request(struct virtqueue /* Die, bad Guest, die. */ errx(1, "Write past end %llu+%u", off, ret); } + + wlen = sizeof(*in); + *in = (ret >= 0 ? VIRTIO_BLK_S_OK : VIRTIO_BLK_S_IOERR); + } else if (out->type & VIRTIO_BLK_T_FLUSH) { + /* Flush */ + ret = fdatasync(vblk->fd); + verbose("FLUSH fdatasync: %i\n", ret); wlen = sizeof(*in); *in = (ret >= 0 ? VIRTIO_BLK_S_OK : VIRTIO_BLK_S_IOERR); } else { @@ -1702,15 +1700,6 @@ static void blk_request(struct virtqueue } } - /* - * OK, so we noted that it was pretty poor to use an fdatasync as a - * barrier. But Christoph Hellwig points out that we need a sync - * *afterwards* as well: "Barriers specify no reordering to the front - * or the back." And Jens Axboe confirmed it, so here we are: - */ - if (out->type & VIRTIO_BLK_T_BARRIER) - fdatasync(vblk->fd); - /* Finished that request. */ add_used(vq, head, wlen); } @@ -1735,8 +1724,8 @@ static void setup_block_file(const char vblk->fd = open_or_die(filename, O_RDWR|O_LARGEFILE); vblk->len = lseek64(vblk->fd, 0, SEEK_END); - /* We support barriers. */ - add_feature(dev, VIRTIO_BLK_F_BARRIER); + /* We support FLUSH. */ + add_feature(dev, VIRTIO_BLK_F_FLUSH); /* Tell Guest how many sectors this device has. */ conf.capacity = cpu_to_le64(vblk->len / 512);