From: Nathan Bossart <nathandbossart@gmail.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Justin Pryzby <pryzby@telsasoft.com>
Cc: Thomas Munro <thomas.munro@gmail.com>
Cc: David Steele <david@pgmasters.net>
Cc: Fujii Masao <masao.fujii@oss.nttdata.com>
Cc: Bruce Momjian <bruce@momjian.us>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Michael Brown <michael.brown@discourse.org>
Cc: pgsql-hackers@postgresql.org
Subject: Re: should frontend tools use syncfs() ?
Date: Wed, 16 Aug 2023 08:23:25 -0700
Message-ID: <20230816152325.GC2651383@nathanxps13> (raw)
In-Reply-To: <20230816151705.GB2651383@nathanxps13>
References: <20210930004340.GM831@telsasoft.com>
<YVUz0Ay9KshniWBe@paquier.xyz>
<20220413115412.GM26620@telsasoft.com>
<20230729214010.GA189456@nathanxps13>
<20230731175138.GA432880@nathanxps13>
<20230731183946.GB537853@nathanxps13>
<20230801163707.GA862840@nathanxps13>
<20230808200606.GA1384393@nathanxps13>
<ZNwF0u/89JFUOQiM@paquier.xyz>
<20230816151705.GB2651383@nathanxps13>
On Wed, Aug 16, 2023 at 08:17:05AM -0700, Nathan Bossart wrote:
> On Wed, Aug 16, 2023 at 08:10:10AM +0900, Michael Paquier wrote:
>> + pg_log_error("could not synchronize file system for file \"%s\": %m", path);
>> + (void) close(fd);
>> + exit(EXIT_FAILURE);
>>
>> walkdir() reports errors and does not consider these fatal. Why the
>> early exit()?
>
> I know it claims to, but fsync_fname() does exit when fsync() fails:
>
> returncode = fsync(fd);
>
> /*
> * Some OSes don't allow us to fsync directories at all, so we can ignore
> * those errors. Anything else needs to be reported.
> */
> if (returncode != 0 && !(isdir && (errno == EBADF || errno == EINVAL)))
> {
> pg_log_error("could not fsync file \"%s\": %m", fname);
> (void) close(fd);
> exit(EXIT_FAILURE);
> }
>
> I suspect that the current code does not treat failures for things like
> open() as fatal because it's likely due to a lack of permissions on the
> file, but it does treat failures to fsync() as fatal because it is more
> likely to indicate that Ń•omething is very wrong. I don't know whether this
> reasoning is sound, but I tried to match the current convention in the
> syncfs() code.
Ah, it looks like this code used to treat fsync() errors as non-fatal, but
it was changed in commit 1420617. I still find it a bit strange that some
errors that prevent a file from being sync'd are non-fatal while others
_are_ fatal, but that is probably a topic for another thread.
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
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To: pgsql-hackers@postgresql.org
Cc: nathandbossart@gmail.com, michael@paquier.xyz, pryzby@telsasoft.com, thomas.munro@gmail.com, david@pgmasters.net, masao.fujii@oss.nttdata.com, bruce@momjian.us, tgl@sss.pgh.pa.us, michael.brown@discourse.org
Subject: Re: should frontend tools use syncfs() ?
In-Reply-To: <20230816152325.GC2651383@nathanxps13>
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