Re: [Qemu-devel] IDE disk FLUSH take more than 30 secs, the SUSE guest reports "lost interrupt and the file system becomes read-only"

[Stefan Hajnoczi]

On Sun, May 26, 2013 at 07:08:02PM +0200, Andreas Färber wrote:
> Am 21.05.2013 09:12, schrieb Gonglei (Arei):
> > Through analysis, I found that because the system call the fdatasync 
> > command in the Qemu over 30s, 
> > after the Guest's kernel thread detects the io transferation is timeout, 
> > went to check IDE disk state. 
> > But the IDE disk status is 0x50, rather than the BSY status, and then 
> > departed error process...
> > 
> > the path of kernel's action is :
> > scsi_softirq_done
> >  scsi_eh_scmd_add
> >    scsi_error_handler
> >      shost->transportt->eh_strategy_handler 
> >             ata_scsi_error 
> >                     ap->ops->lost_interrupt
> >                             ata_sff_lost_interrupt
> > Finally, the file system becomes read-only.
> > 
> > Why not set the IDE disk for the BSY status When 0xe7 command is executed 
> > in the Qemu?
> 
> Have you actually tried that out with a patch such as the following?
> 
> diff --git a/hw/ide/core.c b/hw/ide/core.c
> index c7a8041..bf1ff18 100644
> --- a/hw/ide/core.c
> +++ b/hw/ide/core.c
> @@ -795,6 +795,8 @@ static void ide_flush_cb(void *opaque, int ret)
>  {
>      IDEState *s = opaque;
> 
> +    s->status &= ~BUSY_STAT;
> +
>      if (ret < 0) {
>          /* XXX: What sector number to set here? */
>          if (ide_handle_rw_error(s, -ret, BM_STATUS_RETRY_FLUSH)) {
> @@ -814,6 +816,7 @@ void ide_flush_cache(IDEState *s)
>          return;
>      }
> 
> +    s->status |= BUSY_STAT;
>      bdrv_acct_start(s->bs, &s->acct, 0, BDRV_ACCT_FLUSH);
>      bdrv_aio_flush(s->bs, ide_flush_cb, s);
>  }
> 
> No clue if this is spec-compliant. ;)
> 
> Note however that qemu_fdatasync() is done in the flush callback of
> block/raw-posix.c, so IIUC everything calling bdrv_aio_flush() or
> bdrv_flush_all() may potentially run into issues beyond just ATA:

This is an IDE emulation bug.  virtio-blk, for example, doesn't have
this kind of busy status bit.  It's probably not an issue with SCSI
either.

Stefan