Am 01.02.2012 04:06, schrieb Supriya Kannery:
> Struct BDRVReopenState along with three reopen related functions
> introduced for handling reopening of images safely. This can be
> extended by each of the block drivers to reopen respective
> image files.
>
> Signed-off-by: Supriya Kannery <supri...@linux.vnet.ibm.com>
>
> Index: qemu/block.c
> ===================================================================
> --- qemu.orig/block.c
> +++ qemu/block.c
> @@ -808,10 +808,32 @@ unlink_and_fail:
> return ret;
> }
>
> +int bdrv_reopen_prepare(BlockDriverState *bs, BDRVReopenState **prs, int
> flags)
> +{
> + BlockDriver *drv = bs->drv;
> +
> + return drv->bdrv_reopen_prepare(bs, prs, flags);
> +}
> +
> +void bdrv_reopen_commit(BlockDriverState *bs, BDRVReopenState *rs)
> +{
> + BlockDriver *drv = bs->drv;
> +
> + drv->bdrv_reopen_commit(bs, rs);
> +}
> +
> +void bdrv_reopen_abort(BlockDriverState *bs, BDRVReopenState *rs)
> +{
> + BlockDriver *drv = bs->drv;
> +
> + drv->bdrv_reopen_abort(bs, rs);
> +}
> +
> int bdrv_reopen(BlockDriverState *bs, int bdrv_flags)
> {
> BlockDriver *drv = bs->drv;
> int ret = 0, open_flags;
> + BDRVReopenState *reopen_state = NULL;
>
> /* Quiesce IO for the given block device */
> qemu_aio_flush();
> @@ -820,17 +842,32 @@ int bdrv_reopen(BlockDriverState *bs, in
> qerror_report(QERR_DATA_SYNC_FAILED, bs->device_name);
> return ret;
> }
> - open_flags = bs->open_flags;
> - bdrv_close(bs);
>
> - ret = bdrv_open(bs, bs->filename, bdrv_flags, drv);
> - if (ret < 0) {
> - /* Reopen failed. Try to open with original flags */
> - qerror_report(QERR_REOPEN_FILE_FAILED, bs->filename);
> - ret = bdrv_open(bs, bs->filename, open_flags, drv);
> + /* Use driver specific reopen() if available */
> + if (drv->bdrv_reopen_prepare) {
> + ret = bdrv_reopen_prepare(bs, &reopen_state, bdrv_flags);
> + if (ret < 0) {
> + bdrv_reopen_abort(bs, reopen_state);
> + qerror_report(QERR_REOPEN_FILE_FAILED, bs->filename);
> + return ret;
> + }
> +
> + bdrv_reopen_commit(bs, reopen_state);
> + bs->open_flags = bdrv_flags;
> +
> + } else {
> + open_flags = bs->open_flags;
> + bdrv_close(bs);
> +
> + ret = bdrv_open(bs, bs->filename, bdrv_flags, drv);
> if (ret < 0) {
> - /* Reopen failed with orig and modified flags */
> - abort();
> + /* Reopen failed. Try to open with original flags */
> + qerror_report(QERR_REOPEN_FILE_FAILED, bs->filename);
> + ret = bdrv_open(bs, bs->filename, open_flags, drv);
> + if (ret < 0) {
> + /* Reopen failed with orig and modified flags */
> + bs->drv = NULL;
> + }
> }
Most image formats don't have a bdrv_reopen_* implementation after this
series, so usually you'll have something like qcow2 on top of file. This
code uses bdrv_close/open for the whole stack, even though the file
layer could actually make use of a bdrv_reopen_* implementation and the
qcow2 open isn't likely to fail if the image file could be opened.
I think we can use drv->bdrv_close/open to reopen only one layer and try
using bdrv_reopen_* for the lower layer again.
This is an improvement that can be done in a separate patch, though.
Kevin
