From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50825) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WNNSo-0007tV-Ug for qemu-devel@nongnu.org; Tue, 11 Mar 2014 10:15:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WNNSi-0000zv-Eh for qemu-devel@nongnu.org; Tue, 11 Mar 2014 10:15:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:23236) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WNNSi-0000zc-6a for qemu-devel@nongnu.org; Tue, 11 Mar 2014 10:15:20 -0400 Received: from int-mx02.intmail.prod.int.phx2.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id s2BEFGg4026938 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Tue, 11 Mar 2014 10:15:17 -0400 From: Kevin Wolf Date: Tue, 11 Mar 2014 15:15:03 +0100 Message-Id: <1394547303-9154-1-git-send-email-kwolf@redhat.com> Subject: [Qemu-devel] [PATCH] qcow2: Don't write with BDRV_O_INCOMING List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: kwolf@redhat.com, stefanha@redhat.com qcow2_open() causes writes when repairing an image with the dirty flag set and when clearing autoclear flags. It shouldn't do this when another qemu instance is still actively working on this image file. One effect of the bug is that images may have a cleared dirty flag while the migration source host still has it in use with lazy refcounts enabled, so refcounts are not accurate and the dirty flag must remain set. Signed-off-by: Kevin Wolf --- block/qcow2.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/block/qcow2.c b/block/qcow2.c index b5b1e8c..da82646 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -644,7 +644,7 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags, } /* Clear unknown autoclear feature bits */ - if (!bs->read_only && s->autoclear_features != 0) { + if (!bs->read_only && !(flags & BDRV_O_INCOMING) && s->autoclear_features) { s->autoclear_features = 0; ret = qcow2_update_header(bs); if (ret < 0) { @@ -657,7 +657,7 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags, qemu_co_mutex_init(&s->lock); /* Repair image if dirty */ - if (!(flags & BDRV_O_CHECK) && !bs->read_only && + if (!(flags & (BDRV_O_CHECK | BDRV_O_INCOMING)) && !bs->read_only && (s->incompatible_features & QCOW2_INCOMPAT_DIRTY)) { BdrvCheckResult result = {0}; @@ -1137,10 +1137,12 @@ static void qcow2_close(BlockDriverState *bs) /* else pre-write overlap checks in cache_destroy may crash */ s->l1_table = NULL; - qcow2_cache_flush(bs, s->l2_table_cache); - qcow2_cache_flush(bs, s->refcount_block_cache); + if (!(bs->open_flags & BDRV_O_INCOMING)) { + qcow2_cache_flush(bs, s->l2_table_cache); + qcow2_cache_flush(bs, s->refcount_block_cache); - qcow2_mark_clean(bs); + qcow2_mark_clean(bs); + } qcow2_cache_destroy(bs, s->l2_table_cache); qcow2_cache_destroy(bs, s->refcount_block_cache); -- 1.8.1.4