Re: [Qemu-devel] [PATCH v3 3/3] scsi-block: Support rerror/werror

[Paolo Bonzini <pbonzini@redhat.com>]

On 18/08/2017 16:15, Fam Zheng wrote:
> This makes the werror/rerror options available on the scsi-block device,
> to allow user specify error handling policy similar to scsi-hd.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  hw/scsi/scsi-disk.c | 54 +++++++++++++++++++++++++++++++++++++++--------------
>  1 file changed, 40 insertions(+), 14 deletions(-)
> 
> diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
> index 5f1e5e8070..ec7dbe4a2d 100644
> --- a/hw/scsi/scsi-disk.c
> +++ b/hw/scsi/scsi-disk.c
> @@ -39,6 +39,7 @@ do { printf("scsi-disk: " fmt , ## __VA_ARGS__); } while (0)
>  #include "hw/block/block.h"
>  #include "sysemu/dma.h"
>  #include "qemu/cutils.h"
> +#include "scsi/scsi.h"
>  
>  #ifdef __linux
>  #include <scsi/sg.h>
> @@ -106,7 +107,7 @@ typedef struct SCSIDiskState
>      bool tray_locked;
>  } SCSIDiskState;
>  
> -static int scsi_handle_rw_error(SCSIDiskReq *r, int error, bool acct_failed);
> +static bool scsi_handle_rw_error(SCSIDiskReq *r, int error, bool acct_failed);
>  
>  static void scsi_free_request(SCSIRequest *req)
>  {
> @@ -184,19 +185,10 @@ static bool scsi_disk_req_check_error(SCSIDiskReq *r, int ret, bool acct_failed)
>          return true;
>      }
>  
> -    if (ret < 0) {
> +    if (ret < 0 || (r->status && *r->status)) {
>          return scsi_handle_rw_error(r, -ret, acct_failed);
>      }
>  
> -    if (r->status && *r->status) {
> -        if (acct_failed) {
> -            SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
> -            block_acct_failed(blk_get_stats(s->qdev.conf.blk), &r->acct);
> -        }
> -        scsi_req_complete(&r->req, *r->status);
> -        return true;
> -    }
> -
>      return false;
>  }
>  
> @@ -422,13 +414,13 @@ static void scsi_read_data(SCSIRequest *req)
>  }
>  
>  /*
> - * scsi_handle_rw_error has two return values.  0 means that the error
> - * must be ignored, 1 means that the error has been processed and the
> + * scsi_handle_rw_error has two return values.  False means that the error
> + * must be ignored, true means that the error has been processed and the
>   * caller should not do anything else for this request.  Note that
>   * scsi_handle_rw_error always manages its reference counts, independent
>   * of the return value.
>   */
> -static int scsi_handle_rw_error(SCSIDiskReq *r, int error, bool acct_failed)
> +static bool scsi_handle_rw_error(SCSIDiskReq *r, int error, bool acct_failed)
>  {
>      bool is_read = (r->req.cmd.mode == SCSI_XFER_FROM_DEV);
>      SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
> @@ -440,6 +432,11 @@ static int scsi_handle_rw_error(SCSIDiskReq *r, int error, bool acct_failed)
>              block_acct_failed(blk_get_stats(s->qdev.conf.blk), &r->acct);
>          }
>          switch (error) {
> +        case 0:
> +            /* The command has run, no need to fake sense.  */
> +            assert(r->status && *r->status);
> +            scsi_req_complete(&r->req, *r->status);
> +            break;
>          case ENOMEDIUM:
>              scsi_check_condition(r, SENSE_CODE(NO_MEDIUM));
>              break;
> @@ -457,6 +454,34 @@ static int scsi_handle_rw_error(SCSIDiskReq *r, int error, bool acct_failed)
>              break;
>          }
>      }
> +    if (!error) {
> +        int key, asc, ascq;
> +        assert(r->status && *r->status);
> +        switch (r->req.sense[0]) {
> +        case 0x70: /* Fixed format sense data. */
> +            key = r->req.sense[2] & 0xF;
> +            asc = r->req.sense[12];
> +            ascq = r->req.sense[13];
> +            error = scsi_sense_to_errno(key, asc, ascq);
> +            break;
> +        case 0x72: /* Descriptor format sense data. */
> +            key = r->req.sense[1] & 0xF;
> +            asc = r->req.sense[2];
> +            ascq = r->req.sense[3];
> +            error = scsi_sense_to_errno(key, asc, ascq);
> +            break;
> +        default:
> +            error = EIO;
> +            break;
> +        }

Maybe this switch statement should also be a function in util/iscsi.c
(scsi_sense_buf_to_errno)?
> +
> +        if (error == ECANCELED) {

... || error == EAGAIN || error == ENOTCONN || error == 0

?

> +            /* Command aborted shouldn't stop the VM. */
> +            scsi_req_complete(&r->req, *r->status);
> +            return true;
> +        }
> +    }
> +
>      blk_error_action(s->qdev.conf.blk, action, is_read, error);
>      if (action == BLOCK_ERROR_ACTION_STOP) {
>          scsi_req_retry(&r->req);
> @@ -2972,6 +2997,7 @@ static const TypeInfo scsi_cd_info = {
>  
>  #ifdef __linux__
>  static Property scsi_block_properties[] = {
> +    DEFINE_BLOCK_ERROR_PROPERTIES(SCSIDiskState, qdev.conf),         \
>      DEFINE_PROP_DRIVE("drive", SCSIDiskState, qdev.conf.blk),
>      DEFINE_PROP_END_OF_LIST(),
>  };
>