Date: Sun, 22 May 2016 16:26:34 -0700 From: Conrad Meyer <cem@FreeBSD.org> To: Dirk Engling <erdgeist@erdgeist.org>, FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: read(2) and thus bsdiff is limited to 2^31 bytes Message-ID: <CAG6CVpWbYTBQCVQ5Eu576Tx6%2Bvd03RskkcF8UemVNeq%2BVF8Mvg@mail.gmail.com> In-Reply-To: <20160522231048.GA25503@britannica.bec.de> References: <b2515cae-b75d-66e9-4207-3cf100ab3ab0@erdgeist.org> <CAG6CVpWb7nvX%2BLFpLizkSx8Y-deXfXiWi=rL56iGZ71YPhmLbw@mail.gmail.com> <20160522231048.GA25503@britannica.bec.de>
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On Sun, May 22, 2016 at 4:10 PM, Joerg Sonnenberger <joerg@bec.de> wrote: > On Sun, May 22, 2016 at 03:56:33PM -0700, Conrad Meyer wrote: >> ERRORS >> The read(), readv(), pread() and preadv() system calls will succeed >> unless: >> ... >> [EINVAL] The value nbytes is greater than INT_MAX. >> >> It does seem silly to me given nbytes is a size_t. I think it should >> error if nbytes is greater than SSIZE_T_MAX, but on platforms where >> size_t is larger than int (e.g. amd64) it shouldn't error for nbytes >> in [INT_MAX, SSIZE_T_MAX - 1]. > > There are a lot of valid reasons for not doing arbitrarily large > operations, especially since a certain amount of atomicity is expected > for local IO. That doesn't mean that it can't be turned into a short > read/write instead. Erroring out seeems completely unjustified. Sure; those reasons also apply to INT_MAX-sized IOs (2 GB). Conrad
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