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block/vhdx.c: Don't blindly update the header

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The VHDX specification requires that before user data modification of
the vhdx image, the VHDX header file and data GUIDs need to be updated.
In vhdx_open(), if the image is set to RDWR, we go ahead and update the
header.

However, just because the image is set to RDWR does not mean we can go
ahead and write at this point - specifically, if the QEMU run state is
INMIGRATE, the underlying file BS may be set to inactive via the BDS
open flag of BDRV_O_INACTIVE.  Attempting to write under this condition
will cause an assert in bdrv_co_pwritev().

We can alternatively latch the first time the image is written.  And lo
and behold, we do just that, via vhdx_user_visible_write() in
vhdx_co_writev().  This means the call to vhdx_update_headers() in
vhdx_open() is likely just vestigial, and can be removed.

Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Tested-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Jeff Cody <jcody@redhat.com>
Message-id: 659e4cdba6ef4c651737852777c8c93d27b38040.1510059970.git.jcody@redhat.com
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Jeff Cody 2017-11-07 08:10:33 -05:00 committed by Max Reitz
parent d04c155503
commit 7479bf07c4
1 changed files with 0 additions and 7 deletions
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block/vhdx.c
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@ -1008,13 +1008,6 @@ static int vhdx_open(BlockDriverState *bs, QDict *options, int flags,
goto fail;
}
if (flags & BDRV_O_RDWR) {
ret = vhdx_update_headers(bs, s, false, NULL);
if (ret < 0) {
goto fail;
}
}
/* TODO: differencing files */
return 0;