From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=55461 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Pfjuu-0007ib-Ai for qemu-devel@nongnu.org; Wed, 19 Jan 2011 21:06:29 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Pfjut-0008Un-2z for qemu-devel@nongnu.org; Wed, 19 Jan 2011 21:06:28 -0500 Received: from mail-wy0-f173.google.com ([74.125.82.173]:44916) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Pfjus-0008Uh-SW for qemu-devel@nongnu.org; Wed, 19 Jan 2011 21:06:27 -0500 Received: by wyg36 with SMTP id 36so103838wyg.4 for ; Wed, 19 Jan 2011 18:06:26 -0800 (PST) MIME-Version: 1.0 Sender: tamura.yoshiaki@gmail.com In-Reply-To: <1295449188-17877-1-git-send-email-Pierre.Riteau@irisa.fr> References: <1295449188-17877-1-git-send-email-Pierre.Riteau@irisa.fr> Date: Thu, 20 Jan 2011 11:06:26 +0900 Message-ID: Subject: Re: [Qemu-devel] [PATCH] Fix block migration when the device size is not a multiple of 1 MB From: Yoshiaki Tamura Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Pierre Riteau Cc: kwolf@redhat.com, qemu-devel@nongnu.org 2011/1/19 Pierre Riteau : > b02bea3a85cc939f09aa674a3f1e4f36d418c007 added a check on the return > value of bdrv_write and aborts migration when it fails. However, if the > size of the block device to migrate is not a multiple of BLOCK_SIZE > (currently 1 MB), the last bdrv_write will fail with -EIO. > > Fixed by calling bdrv_write with the correct size of the last block. > --- > =A0block-migration.c | =A0 16 +++++++++++++++- > =A01 files changed, 15 insertions(+), 1 deletions(-) > > diff --git a/block-migration.c b/block-migration.c > index 1475325..eeb9c62 100644 > --- a/block-migration.c > +++ b/block-migration.c > @@ -635,6 +635,8 @@ static int block_load(QEMUFile *f, void *opaque, int = version_id) > =A0 =A0 int64_t addr; > =A0 =A0 BlockDriverState *bs; > =A0 =A0 uint8_t *buf; > + =A0 =A0int64_t total_sectors; > + =A0 =A0int nr_sectors; > > =A0 =A0 do { > =A0 =A0 =A0 =A0 addr =3D qemu_get_be64(f); > @@ -656,10 +658,22 @@ static int block_load(QEMUFile *f, void *opaque, in= t version_id) > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 return -EINVAL; > =A0 =A0 =A0 =A0 =A0 =A0 } > > + =A0 =A0 =A0 =A0 =A0 =A0total_sectors =3D bdrv_getlength(bs) >> BDRV_SEC= TOR_BITS; > + =A0 =A0 =A0 =A0 =A0 =A0if (total_sectors <=3D 0) { > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0fprintf(stderr, "Error getting length of= block device %s\n", device_name); > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0return -EINVAL; > + =A0 =A0 =A0 =A0 =A0 =A0} > + > + =A0 =A0 =A0 =A0 =A0 =A0if (total_sectors - addr < BDRV_SECTORS_PER_DIRT= Y_CHUNK) { > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0nr_sectors =3D total_sectors - addr; > + =A0 =A0 =A0 =A0 =A0 =A0} else { > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0nr_sectors =3D BDRV_SECTORS_PER_DIRTY_CH= UNK; > + =A0 =A0 =A0 =A0 =A0 =A0} > + > =A0 =A0 =A0 =A0 =A0 =A0 buf =3D qemu_malloc(BLOCK_SIZE); > > =A0 =A0 =A0 =A0 =A0 =A0 qemu_get_buffer(f, buf, BLOCK_SIZE); > - =A0 =A0 =A0 =A0 =A0 =A0ret =3D bdrv_write(bs, addr, buf, BDRV_SECTORS_P= ER_DIRTY_CHUNK); > + =A0 =A0 =A0 =A0 =A0 =A0ret =3D bdrv_write(bs, addr, buf, nr_sectors); > > =A0 =A0 =A0 =A0 =A0 =A0 qemu_free(buf); > =A0 =A0 =A0 =A0 =A0 =A0 if (ret < 0) { > -- > 1.7.3.5 > > > Hi Pierre, I don't think the fix above is correct. If you have a file which isn't aliened with BLOCK_SIZE, you won't get an error with the patch. However, the receiver doesn't know how much sectors which the sender wants to be written, so the guest may fail after migration because some data may not be written. IIUC, although changing bytestream should be prevented as much as possible, we should save/load total_sectors to check appropriate file is allocated on the receiver side. BTW, you should use error_report instead of fprintf(stderr, ...). Thanks, Yoshi