Re: [Qemu-devel] [v9 Patch 5/6]Qemu: Framework for reopening images safely

[Luiz Capitulino <lcapitulino@redhat.com>]

On Fri, 11 Nov 2011 12:18:18 +0530
Supriya Kannery <supriyak@linux.vnet.ibm.com> wrote:

> Struct BDRVReopenState along with three reopen related functions
> introduced for handling reopen state of images safely. This can be
> extended by each of the block drivers to reopen respective
> image files.

Shouldn't this patch come before the one introducing the QMP command?

> 
> Signed-off-by: Supriya Kannery <supriyak@linux.vnet.ibm.com>
> 
> Index: qemu/block.c
> ===================================================================
> --- qemu.orig/block.c
> +++ qemu/block.c
> @@ -696,10 +696,33 @@ 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, int flags)
> +{
> +    BlockDriver *drv = bs->drv;
> +
> +    drv->bdrv_reopen_commit(bs, rs, flags);
> +    bs->open_flags = flags;
> +}
> +
> +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();
> @@ -708,17 +731,31 @@ 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, 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;
> +            }
>          }
>      }
>  
> Index: qemu/block_int.h
> ===================================================================
> --- qemu.orig/block_int.h
> +++ qemu/block_int.h
> @@ -56,6 +56,14 @@ struct BlockDriver {
>      int (*bdrv_probe)(const uint8_t *buf, int buf_size, const char *filename);
>      int (*bdrv_probe_device)(const char *filename);
>      int (*bdrv_open)(BlockDriverState *bs, int flags);
> +
> +    /* For handling image reopen for split or non-split files */
> +    int (*bdrv_reopen_prepare)(BlockDriverState *bs,
> +                               BDRVReopenState **prs,
> +                               int flags);
> +    void (*bdrv_reopen_commit)(BlockDriverState *bs, BDRVReopenState *rs,
> +                               int flags);
> +    void (*bdrv_reopen_abort)(BlockDriverState *bs, BDRVReopenState *rs);
>      int (*bdrv_file_open)(BlockDriverState *bs, const char *filename, int flags);
>      int (*bdrv_read)(BlockDriverState *bs, int64_t sector_num,
>                       uint8_t *buf, int nb_sectors);
> @@ -213,6 +221,11 @@ struct BlockDriverState {
>      void *private;
>  };
>  
> +struct BDRVReopenState {
> +    BlockDriverState *bs;
> +    int reopen_flags;
> +};
> +
>  struct BlockDriverAIOCB {
>      AIOPool *pool;
>      BlockDriverState *bs;
> Index: qemu/qemu-common.h
> ===================================================================
> --- qemu.orig/qemu-common.h
> +++ qemu/qemu-common.h
> @@ -203,6 +203,7 @@ typedef struct NICInfo NICInfo;
>  typedef struct HCIInfo HCIInfo;
>  typedef struct AudioState AudioState;
>  typedef struct BlockDriverState BlockDriverState;
> +typedef struct BDRVReopenState BDRVReopenState;
>  typedef struct DriveInfo DriveInfo;
>  typedef struct DisplayState DisplayState;
>  typedef struct DisplayChangeListener DisplayChangeListener;
> Index: qemu/block.h
> ===================================================================
> --- qemu.orig/block.h
> +++ qemu/block.h
> @@ -105,6 +105,9 @@ int bdrv_file_open(BlockDriverState **pb
>  int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
>                BlockDriver *drv);
>  int bdrv_reopen(BlockDriverState *bs, int bdrv_flags);
> +int bdrv_reopen_prepare(BlockDriverState *bs, BDRVReopenState **prs, int flags);
> +void bdrv_reopen_commit(BlockDriverState *bs, BDRVReopenState *rs,  int flags);
> +void bdrv_reopen_abort(BlockDriverState *bs, BDRVReopenState *rs);
>  void bdrv_close(BlockDriverState *bs);
>  int bdrv_attach_dev(BlockDriverState *bs, void *dev);
>  void bdrv_attach_dev_nofail(BlockDriverState *bs, void *dev);
>