From: rsbecker@nexbridge.com Date: Wed, 08 Apr 2026 22:04:01 GMT Subject: RE: Git 2.54.0-rc1, subtests of t5310, t5326, t5327 Message-ID: <016e01dcc7a3$9f0d06e0$dd2714a0$@nexbridge.com> In-Reply-To: On April 8, 2026 5:43 PM, Junio C Hamano wrote: > writes: > >> On April 8, 2026 4:22 PM, Junio C Hamano wrote: >>> writes: >>> >>>> On my box, I have the following note: >>>> >>>> Specifying the sum of the iov_len values in the iov array greater >>>> than the OSS I/O size limit for that open causes the writev() >>>> function to return -1 and set errno to [EINVAL]. >>> >>>That is unexpected. >>> >>>writev() may fail if the sum of iov_len would not fit within ssize_t >>>with >> EINVAL, but >>>unless your "the OSS I/O size limit" is the same as SSIZE_MAX, what >>>you >> have above >>>is not quite the same. >>> >>>Does your build work with NO_WRITEV=Nope? I think I saw it asked a >>>few >> times >>>but I do not recall seeing it answered. At least we know >>>xwrite() seems to work well enough on your system, which is what the >>>writev() emulation is written in terms of, so I suspect it would. >> >> Yes, NO_WRITEV=Nope does compile and execute. I am including it in our >> CI/CD job for now. Can we plan on a fix for this? > >What I have heard so far indicate that the code that uses writev() would need to >loop over to prepare for short writes, but your >writev() that fails for "the OSS I/O size limit" (whatever it is) does not sound like >something we want to change the callers to chomp the writev() calls into smaller >chunks for. Such a platform is far better off using the compat/writev for the code >path we recently started using writev() in. > >To be quite honest, I am not sure if it is even worth using writev() if we need a loop >that protects against shrot writes, so unless I am grossly mistaken (e.g., perhaps >there is some guarantee that there won't be any short writes for writev() that sends >data smaller than 64k that I missed in the docs), the best course of action might be >to revert the change to use writev() and use the two write(2)s as before, *if* we >actually observe that the current code is broken by short writes. I am 100% sure that EINVAL is returned by writev() on NonStop if the size exceeds 52K In 32-bit models. Whether it supports 868K for 64-bit is conjecture. NO_WRITEV=Nope works, which I am trying for everything at RC1, then we can live with this.