Re: [PATCH v5 0/9] block: Add retry for werror=/rerror= mechanism

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Fri, Feb 05, 2021 at 06:13:06PM +0800, Jiahui Cen wrote:
> This patch series propose to extend the werror=/rerror= mechanism to add
> a 'retry' feature. It can automatically retry failed I/O requests on error
> without sending error back to guest, and guest can get back running smoothly
> when I/O is recovred.

This patch series implements a retry followed by werror/rerror=report
after a timeout. This mechanism could be made more generic (and the code
could be simplified) by removing the new werror/rerror=retry action and
instead implementing the retry/timeout followed by *any* werror=/rerror=
policy chosen by the user.

In other words, if the retry interval is non-zero, retry the request and
check for timeouts. When the timeout is reached, obey the
werror=/rerror= action.

This is more flexible than hard-coding werror=retry to mean retry
timeout followed by werror=report.

For example:

  werror=stop,write-retry-interval=1000,write-retry-timeout=15000,
  rerror=report,read-retry-interval=1000,read-retry-timeout=15000

Failed write requests will be retried once a second for 15 seconds.
If the timeout is reached the guest is stopped.

Failed read requests will be retried once a second for 15 seconds. If
the timeout is reached the error is reported to the guest.

Stefan

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