Blame SOURCES/kvm-block-drive-mirror-Check-for-NULL-backing_hd.patch

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From bcc312ef8d0c8ff3c8743e01bd24fd26c4cc96f6 Mon Sep 17 00:00:00 2001
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From: Max Reitz <mreitz@redhat.com>
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Date: Sun, 19 Jan 2014 18:07:57 +0100
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Subject: [PATCH 23/34] block/drive-mirror: Check for NULL backing_hd
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RH-Author: Max Reitz <mreitz@redhat.com>
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Message-id: <1390154881-17140-4-git-send-email-mreitz@redhat.com>
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Patchwork-id: 56816
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O-Subject: [RHEL-7.0 qemu-kvm PATCH v2 3/7] block/drive-mirror: Check for NULL backing_hd
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Bugzilla: 921890
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Jeffrey Cody <jcody@redhat.com>
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BZ: 921890
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It should be possible to execute the QMP "drive-mirror" command in
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"none" sync mode and "absolute-paths" mode even for block devices
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lacking a backing file.
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"absolute-paths" does in fact not require a backing file to be present,
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as can be seen from the "top" sync mode code path. "top" basically
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states that the device should indeed have a backing file - however, the
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current code catches the case if it doesn't and then simply treats it as
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"full" sync mode, creating a target image without a backing file (in
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"absolute-paths" mode). Thus, "absolute-paths" does not imply the target
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file must indeed have a backing file.
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Therefore, the target file may be left unbacked in case of "none" sync
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mode as well, if the specified device is not backed either. Currently,
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qemu will crash trying to dereference the backing file pointer since it
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assumes that it will always be non-NULL in that case ("none" with
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"absolute-paths").
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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Reviewed-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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(cherry picked from commit 1452686495922b81d6cf43edf025c1aef15965c0)
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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---
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 blockdev.c | 4 +++-
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 1 file changed, 3 insertions(+), 1 deletion(-)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 blockdev.c |    4 +++-
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 1 files changed, 3 insertions(+), 1 deletions(-)
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diff --git a/blockdev.c b/blockdev.c
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index 0ba2504..06bbf30 100644
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--- a/blockdev.c
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+++ b/blockdev.c
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@@ -1611,7 +1611,9 @@ void qmp_drive_mirror(const char *device, const char *target,
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         return;
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     }
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-    if (sync == MIRROR_SYNC_MODE_FULL && mode != NEW_IMAGE_MODE_EXISTING) {
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+    if ((sync == MIRROR_SYNC_MODE_FULL || !source)
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+        && mode != NEW_IMAGE_MODE_EXISTING)
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+    {
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         /* create new image w/o backing file */
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         assert(format && drv);
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         bdrv_img_create(target, format,
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-- 
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1.7.1
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