Re: Patch to improve reliability of postgresql on linux nfs

On Tue, Sep 13, 2011 at 7:30 AM, Florian Pflug <fgp(at)phlo(dot)org> wrote:

>
> Sorry for the self-reply. I realized only after hitting send that I
> got the ENOSPC handling wrong again - we probably ought to check for
> ENOSPC as well as ret == 0. Also, it seems preferable to return the
> number of bytes actually written instead of -1 if we hit an error during
> retry.
>
> With this version, any return value other than <amount> signals an
> error, the number of actually written bytes is reported even in the
> case of an error (to the best of pg_write_nointr's knowledge), and
> errno always indicates the kind of error.

Personally, I'ld think that's ripe for bugs. If the contract is that
ret != amount is the "error" case, then don't return -1 for an error
*sometimes*.

If you sometimes return -1 for an error, even though ret != amount is
the *real* test, I'm going to guess there will be lots of chance for
code to do:
if (pg_write_no_intr(...) < 0)
...

which will only catch some of the errors, and happily continue with the rest...

a.

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