Commit af7b708d authored by Stefan Hajnoczi's avatar Stefan Hajnoczi Committed by Kevin Wolf
Browse files

qcow2: fix autoclear image header update 



The autoclear feature bits can be used for qcow2 file format features
that are safe to "drop" by old programs that do not understand the
feature.  Upon opening the image file unknown autoclear feature bits are
cleared and the image file header is rewritten, but this was happening
too early in the code when critical header fields were not yet loaded.

Process autoclear feature bits after all necessary header information
has been loaded.

Signed-off-by: default avatarStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 093003b1

block/qcow2.c

+9 −8
Original line number Diff line number Diff line
@@ -297,14 +297,6 @@ static int qcow2_open(BlockDriverState *bs, int flags) 
        goto fail;

    }



    if (!bs->read_only && s->autoclear_features != 0) {

        s->autoclear_features = 0;

        ret = qcow2_update_header(bs);

        if (ret < 0) {

            goto fail;

        }

    }



    /* Check support for various header values */

    if (header.refcount_order != 4) {

        report_unsupported(bs, "%d bit reference counts",
@@ -408,6 +400,15 @@ static int qcow2_open(BlockDriverState *bs, int flags) 
        goto fail;

    }



    /* Clear unknown autoclear feature bits */

    if (!bs->read_only && s->autoclear_features != 0) {

        s->autoclear_features = 0;

        ret = qcow2_update_header(bs);

        if (ret < 0) {

            goto fail;

        }

    }



    /* Initialise locks */

    qemu_co_mutex_init(&s->lock);