From: Phillip Wood <phillip.wood123@gmail.com>
Date: Mon, 26 Feb 2024 15:32:14 GMT
Subject: Re: [BUG] 2.44.0 t7704.9 Fails on NonStop ia64
Message-ID: <5e807c1c-20a0-407b-9fc2-acd38521ba45@gmail.com>
In-Reply-To: <01ca01da682a$5f6a7b60$1e3f7220$@nexbridge.com>

Hi Randal

[cc'ing Patrick for the reftable writer]

On 25/02/2024 20:36, rsbecker@nexbridge.com wrote:
> On Sunday, February 25, 2024 2:20 PM, Torsten Bögershausen wrote:
>> On Sun, Feb 25, 2024 at 02:08:35PM -0500, rsbecker@nexbridge.com wrote:
>>> On Sunday, February 25, 2024 1:45 PM, I wrote:
>>>> To: git@vger.kernel.org
>> But I think that this should be used:
>> write_in_full()
> 
> My mailer autocorrected, yes, xwrite. write_in_full() would be safe,
> although a bit redundant since xwrite() does similar things and is used by
> write_in_full().

Note that unlike write_in_full(), xwrite() does not guarantee to write 
the whole buffer passed to it. In general unless a caller is writing a 
single byte or writing less than PIPE_BUF bytes to a pipe it should use 
write_in_full().

> The question is which call is bad? The cruft stuff is
> relatively new and I don't know the code.
> 
>>> reftable/writer.c:              int n = w->write(w->write_arg, zeroed,
>>> w->pending_padding);
>>> reftable/writer.c:      n = w->write(w->write_arg, data, len);

Neither of these appear to check for short writes and 
reftable_fd_write() is a thin wrapper around write(). Maybe 
reftable_fd_write() should be using write_in_full()?

>>> run-command.c:                  len = write(io->fd, io->u.out.buf,

This call to write() looks correct as it is in the io pump loop.

>>> t/helper/test-path-utils.c:                     if (write(1, buffer,
> count)
>>> < 0) >>> t/helper/test-windows-named-pipe.c:             write(1, buf, nbr);
>>> t/helper/test-windows-named-pipe.c:             write(1, buf, nbr);

In principle these all look like they are prone to short writes.

>>> trace2/tr2_dst.c:       bytes = write(fd, buf_line->buf, buf_line->len);

This caller explicitly says it prefers short writes over retrying

Best Wishes

Phillip