Re: [Bug] Git ReadOnly Temp Packfile Causes "Bad file descriptor" And -13 Access Error With NFSv4

From: Jeff King <peff@peff.net>
Date: Feb 11, 2025, 21:39 UTC
Message-ID: <20250211213940.GB3113114@coredump.intra.peff.net>
In-Reply-To: <Z6p-eIxzrFepC3py@tapette.crustytoothpaste.net>

On Mon, Feb 10, 2025 at 10:32:24PM +0000, brian m. carlson wrote:

Show 6 quoted lines

> > This is an issue for active/passive HA file servers. Since NFSv4 evaluates file permissions at the time of opening a file, this FD will always get an access denied error if a failover occurs during git clone.
> 
> I'm not sure there's even a good way to solve this problem on the Git
> side, since I suspect that if we opened the file as 0644 and then
> immediately did an fchmod to 0444, if you'd still fail here if the file
> is reopened.  Is that correct?

We could probably create and write the tempfile as 0644, and then switch it to 0444 before renaming it into place. We already do something similar with adjust_shared_perm(), I think.

I don't know if it's worth doing it that way or not. It should just work even on systems that are happy with the current code, so I think the only downside would be a few extra lines of code and an extra chmod() syscall.

-Peff