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Wed, 8 Apr 2026 14:12:56 -0400 (EDT) From: Junio C Hamano To: Jeff King Cc: rsbecker@nexbridge.com, git@vger.kernel.org Subject: Re: Git 2.54.0-rc1, subtests of t5310, t5326, t5327 In-Reply-To: <20260408173949.GB2850002@coredump.intra.peff.net> (Jeff King's message of "Wed, 8 Apr 2026 13:39:49 -0400") References: <00f401dcc6e6$7183c0f0$548b42d0$@nexbridge.com> <20260408041716.GA1324339@coredump.intra.peff.net> <011701dcc767$8c2ab400$a4801c00$@nexbridge.com> <013301dcc774$5e9fffb0$1bdfff10$@nexbridge.com> <20260408173949.GB2850002@coredump.intra.peff.net> Date: Wed, 08 Apr 2026 11:12:54 -0700 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Jeff King writes: > On Wed, Apr 08, 2026 at 12:25:47PM -0400, rsbecker@nexbridge.com wrote: > >> This is also impacting t5608 and t7700. Anywhere where writev() is >> used, seemingly. We went through MAX_IO_SIZE issues years ago, instead >> of using ssize_t as a basis of how big communication is. I think >> writev() is not valid. It worked on Lunix, but had issues elsewhere. >> This broke the compat layer. > > I wondered briefly if the problem could be that we're violating > MAX_IO_SIZE here, as our use of writev() does not respect it at all. But > the only spot that uses it is feeding pkt-line packets, which max out at > 64k. So unless your MAX_IO_SIZE is smaller than that, I doubt that is > the problem. Good point. The original did not use write(2) directly but used write_or_die(), that is write_in_full(), that loops over xwrite(), so it would have worked even with a lot lower MAX_IO_SIZE limit. According to man7.org, writev() is allowed to transfer fewer bytes than requested, so our use of writev() may have to be a bit more careful, though.