Re: [Qemu-devel] [PATCH] ide: Set BSY bit during FLUSH

[Kevin Wolf <kwolf@redhat.com>]

Am 28.05.2013 um 10:18 hat Andreas Färber geschrieben:
> The implementation of the ATA FLUSH command invokes a flush at the block
> layer, which may on raw files on POSIX entail a synchronous fdatasync().
> This may in some cases take so long that the SLES 11 SP1 guest driver
> reports I/O errors and filesystems get corrupted or remounted read-only.
> 
> Avoid this by setting BUSY_STAT, so that the guest is made aware we are
> in the middle of an operation and no ATA commands are attempted to be
> processed concurrently.
> 
> Addresses BNC#637297.
> 
> Suggested-by: Gonglei (Arei) <arei.gonglei@huawei.com>
> Signed-off-by: Andreas Färber <afaerber@suse.de>
> ---
>  hw/ide/core.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> 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;
> +

This part is unnecessary, the status is already reset.

>      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);
>  }

This should fix the bug, however in an one-off way. I was planning to
fix it by setting BSY for all commands and having an explicit command
completion everywhere. This part is a mess currently in IDE.

The other part why I haven't sent a fix yet is that I don't have a test
case for it. I guess I need to extend blkdebug first before this can be
reliably tested by qtest.

Kevin