Re: Postgres, fsync, and OSs (specifically linux)

On Sat, Apr 28, 2018 at 12:28 AM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> Before linux v4.13 errors in kernel writeback would be reported at most
> once, without a guarantee that that'd happen (IIUC memory pressure could
> lead to the relevant information being evicted) - but it was pretty
> likely. After v4.13 (see https://lwn.net/Articles/724307/) errors are
> reported exactly once to all open file descriptors for a file with an
> error - but never for files that have been opened after the error
> occurred.

snip

> == Proposed Linux Changes ==
>
> - Matthew Wilcox proposed (and posted a patch) that'd partially revert
> behaviour to the pre v4.13 world, by *also* reporting errors to
> "newer" file-descriptors if the error hasn't previously been
> reported. That'd still not guarantee that the error is reported
> (memory pressure could evict information without open fd), but in most
> situations we'll again get the error in the checkpointer.
>
> This seems largely be agreed upon. It's unclear whether it'll go into
> the stable backports for still-maintained >= v4.13 kernels.

This is now merged, if it's not reverted it will appear in v4.17.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fff75eb2a08c2ac96404a2d79685668f3cf5a7a3

The commit is cc-ed to stable so it should get picked up in the near future.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b4678df184b314a2bd47d2329feca2c2534aa12b