Commit ba2ab2f2 authored by Max Reitz's avatar Max Reitz Committed by Kevin Wolf
Browse files

qcow2: Flush image after creation 



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: default avatarMax Reitz <mreitz@redhat.com>
Reviewed-by: default avatarEric Blake <eblake@redhat.com>
Reviewed-by: default avatarBenoit Canet <benoit@irqsave.net>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent ab6f2bbb

block/qcow2.c

+10 −0
Original line number Diff line number Diff line
@@ -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);