Hi, Thanks for the bug report and nice reproducer!
Ricardo Wurmus <rek...@elephly.net> skribis: > The guix-daemon's libutil/util.cc uses copy_file_range to copy a > downloaded file into the store. copy_file_range fails on files larger > than 4GB with an error like this: > > guix build: error: short write in copy_file_range `15' to `16': No such > file or directory > > The man page for copy_file_range says that it could return EFBIG when > the range exceeds the maximum range. The daemon code does not check any > limits and will attempt to copy the whole file. > > I believe our code ought to check the value of st.size and fall back to > a boring copy if it exceeds some "reasonable" value. The goal leading to this error message looks like this: copy_file_range(15, NULL, 16, NULL, 4294967297, 0) = 2147479552 … which is precisely 2 GiB - 4 KiB. Reading the man page, it’s entirely fine: like ‘write’, ‘copy_file_range’ might copy less than asked for, so it’s really a mistake of mine to assume that short writes can’t happen. Presumably there’s an internal limit here we’re reaching that explains why it won’t copy more than 2 GiB at once. With the following change, we get: newfstatat(15, "", {st_mode=S_IFREG|0644, st_size=4294967297, ...}, AT_EMPTY_PATH) = 0 copy_file_range(15, NULL, 16, NULL, 4294967297, 0) = 2147479552 copy_file_range(15, NULL, 16, NULL, 2147487745, 0) = 2147479552 copy_file_range(15, NULL, 16, NULL, 8193, 0) = 8193 fchown(16, 30001, 30000) = 0 Could you confirm that it works for you? Thanks, Ludo’.
>From efd9f3383756df9959651125c0f2e2e769630851 Mon Sep 17 00:00:00 2001 Message-ID: <efd9f3383756df9959651125c0f2e2e769630851.1715594931.git.l...@gnu.org> From: =?UTF-8?q?Ludovic=20Court=C3=A8s?= <l...@gnu.org> Date: Mon, 13 May 2024 12:02:30 +0200 Subject: [PATCH] =?UTF-8?q?daemon:=20Loop=20over=20=E2=80=98copy=5Ffile=5F?= =?UTF-8?q?range=E2=80=99=20upon=20short=20writes.?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Fixes <https://issues.guix.gnu.org/70877>. * nix/libutil/util.cc (copyFile): Loop over ‘copy_file_range’ instead of throwing upon short write. Reported-by: Ricardo Wurmus <rek...@elephly.net> Change-Id: Id7b8a65ea59006c2d91bc23732309a68665b9ca0 --- nix/libutil/util.cc | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/nix/libutil/util.cc b/nix/libutil/util.cc index 578d6572934..3206dea11b1 100644 --- a/nix/libutil/util.cc +++ b/nix/libutil/util.cc @@ -397,9 +397,14 @@ static void copyFile(int sourceFd, int destinationFd) } else { if (result < 0) throw SysError(format("copy_file_range `%1%' to `%2%'") % sourceFd % destinationFd); - if (result < st.st_size) - throw SysError(format("short write in copy_file_range `%1%' to `%2%'") - % sourceFd % destinationFd); + + /* If 'copy_file_range' copied less than requested, try again. */ + for (ssize_t copied = result; copied < st.st_size; copied += result) { + result = copy_file_range(sourceFd, NULL, destinationFd, NULL, + st.st_size - copied, 0); + if (result < 0) + throw SysError(format("copy_file_range `%1%' to `%2%'") % sourceFd % destinationFd); + } } } base-commit: 89cd778f6a45cd9b43a4dc1f236dcd0a87af955c -- 2.41.0