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qcow2: Flush image after creation

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Opening the qcow2 image with BDRV_O_NO_FLUSH prevents any flushes during
the image creation. This means that the image has not yet been flushed
to disk when qemu-img create exits. This flush is delayed until the next
operation on the image involving opening it without BDRV_O_NO_FLUSH and
closing (or directly flushing) it. For large images and/or images with a
small cluster size and preallocated metadata, this flush may take a
significant amount of time and may occur unexpectedly.

Reopening the image without BDRV_O_NO_FLUSH right before the end of
qcow2_create2() results in hoisting the potentially costly flush into
the image creation, which is expected to take some time (whereas
successive image operations may be not).

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Max Reitz 2013-10-24 20:35:06 +02:00 committed by Kevin Wolf
parent ab6f2bbb28
commit ba2ab2f2ca
1 changed files with 10 additions and 0 deletions
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10
block/qcow2.c
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@ -1584,6 +1584,16 @@ static int qcow2_create2(const char *filename, int64_t total_size,
}
}
bdrv_close(bs);
/* Reopen the image without BDRV_O_NO_FLUSH to flush it before returning */
ret = bdrv_open(bs, filename, NULL,
BDRV_O_RDWR | BDRV_O_CACHE_WB, drv, &local_err);
if (error_is_set(&local_err)) {
error_propagate(errp, local_err);
goto out;
}
ret = 0;
out:
bdrv_unref(bs);