Re: Add pg_file_sync() to adminpack

On Mon, Jan 6, 2020 at 3:42 PM Michael Paquier <michael(at)paquier(dot)xyz> wrote:
>
> On Mon, Jan 06, 2020 at 03:20:13PM +0900, Arthur Zakirov wrote:
> > It isn't case if a file doesn't exist. But if there are no permissions on
> > the file:
> >
> > PANIC: could not open file "testfile": Permissions denied
> > server closed the connection unexpectedly
> >
> > It could be fixed by implementing a function like pg_file_sync_internal() or
> > by making the function fsync_fname_ext() external.
>
> The patch uses stat() to make sure that the file exists and has no
> issues. Though it could be a problem with any kind of TOCTOU-like
> issues (looking at you, Windows, for ENOPERM), so I agree that it
> would make more sense to use pg_fsync() here with a fd opened first.

I agree that it's not good for pg_file_sync() to cause a PANIC.
I updated the patch so that pg_file_sync() uses fsync_fname_ext()
instead of fsync_fname() as Arthur suggested.

It's one of ideas to make pg_file_sync() open the file and directly call
pg_fsync(). But fsync_fname_ext() has already such code and
I'd like to avoid the code duplication.

Attached is the updated version of the patch.

Regards,

--
Fujii Masao