# Copyright (C) 2016-2020 all contributors # License: AGPL-3.0+ # # This allows vfork to be used for spawning subprocesses if # ~/.cache/public-inbox/inline-c is writable or if PERL_INLINE_DIRECTORY # is explicitly defined in the environment (and writable). # Under Linux, vfork can make a big difference in spawning performance # as process size increases (fork still needs to mark pages for CoW use). # Currently, we only use this for code intended for long running # daemons (inside the PSGI code (-httpd) and -nntpd). The short-lived # scripts (-mda, -index, -learn, -init) either use IPC::run or standard # Perl routines. # # There'll probably be more OS-level C stuff here, down the line. # We don't want too many DSOs: https://udrepper.livejournal.com/8790.html package PublicInbox::Spawn; use strict; use parent qw(Exporter); use Symbol qw(gensym); use PublicInbox::ProcessPipe; our @EXPORT_OK = qw/which spawn popen_rd nodatacow_dir/; our @RLIMITS = qw(RLIMIT_CPU RLIMIT_CORE RLIMIT_DATA); my $vfork_spawn = <<'VFORK_SPAWN'; #include #include #include #include #include #include /* some platforms need alloca.h, but some don't */ #if defined(__GNUC__) && !defined(alloca) # define alloca(sz) __builtin_alloca(sz) #endif #include #include /* * From the av_len apidoc: * Note that, unlike what the name implies, it returns * the highest index in the array, so to get the size of * the array you need to use "av_len(av) + 1". * This is unlike "sv_len", which returns what you would expect. */ #define AV2C_COPY(dst, src) do { \ I32 i; \ I32 top_index = av_len(src); \ I32 real_len = top_index + 1; \ I32 capa = real_len + 1; \ dst = alloca(capa * sizeof(char *)); \ for (i = 0; i < real_len; i++) { \ SV **sv = av_fetch(src, i, 0); \ dst[i] = SvPV_nolen(*sv); \ } \ dst[real_len] = 0; \ } while (0) /* needs to be safe inside a vfork'ed process */ static void exit_err(int *cerrnum) { *cerrnum = errno; _exit(1); } /* * unstable internal API. It'll be updated depending on * whatever we'll need in the future. * Be sure to update PublicInbox::SpawnPP if this changes */ int pi_fork_exec(SV *redirref, SV *file, SV *cmdref, SV *envref, SV *rlimref, const char *cd) { AV *redir = (AV *)SvRV(redirref); AV *cmd = (AV *)SvRV(cmdref); AV *env = (AV *)SvRV(envref); AV *rlim = (AV *)SvRV(rlimref); const char *filename = SvPV_nolen(file); pid_t pid; char **argv, **envp; sigset_t set, old, cset; int ret, perrnum, cerrnum = 0; AV2C_COPY(argv, cmd); AV2C_COPY(envp, env); ret = sigfillset(&set); assert(ret == 0 && "BUG calling sigfillset"); ret = sigprocmask(SIG_SETMASK, &set, &old); assert(ret == 0 && "BUG calling sigprocmask to block"); ret = sigemptyset(&cset); assert(ret == 0 && "BUG calling sigemptyset"); ret = sigaddset(&cset, SIGCHLD); assert(ret == 0 && "BUG calling sigaddset for SIGCHLD"); pid = vfork(); if (pid == 0) { int sig; I32 i, child_fd, max = av_len(redir); for (child_fd = 0; child_fd <= max; child_fd++) { SV **parent = av_fetch(redir, child_fd, 0); int parent_fd = SvIV(*parent); if (parent_fd == child_fd) continue; if (dup2(parent_fd, child_fd) < 0) exit_err(&cerrnum); } for (sig = 1; sig < NSIG; sig++) signal(sig, SIG_DFL); /* ignore errors on signals */ if (*cd && chdir(cd) < 0) exit_err(&cerrnum); max = av_len(rlim); for (i = 0; i < max; i += 3) { struct rlimit rl; SV **res = av_fetch(rlim, i, 0); SV **soft = av_fetch(rlim, i + 1, 0); SV **hard = av_fetch(rlim, i + 2, 0); rl.rlim_cur = SvIV(*soft); rl.rlim_max = SvIV(*hard); if (setrlimit(SvIV(*res), &rl) < 0) exit_err(&cerrnum); } /* * don't bother unblocking other signals for now, just SIGCHLD. * we don't want signals to the group taking out a subprocess */ (void)sigprocmask(SIG_UNBLOCK, &cset, NULL); execve(filename, argv, envp); exit_err(&cerrnum); } perrnum = errno; ret = sigprocmask(SIG_SETMASK, &old, NULL); assert(ret == 0 && "BUG calling sigprocmask to restore"); if (cerrnum) { if (pid > 0) waitpid(pid, NULL, 0); pid = -1; errno = cerrnum; } else if (perrnum) { errno = perrnum; } return (int)pid; } VFORK_SPAWN # btrfs on Linux is copy-on-write (COW) by default. As of Linux 5.7, # this still leads to fragmentation for SQLite and Xapian files where # random I/O happens, so we disable COW just for SQLite files and Xapian # directories. Disabling COW disables checksumming, so we only do this # for regeneratable files, and not canonical git storage (git doesn't # checksum refs, only data under $GIT_DIR/objects). my $set_nodatacow = $^O eq 'linux' ? <<'SET_NODATACOW' : ''; #include #include #include #include #include #include #include #include void nodatacow_fd(int fd) { struct statfs buf; int val = 0; if (fstatfs(fd, &buf) < 0) { fprintf(stderr, "fstatfs: %s\\n", strerror(errno)); return; } /* only btrfs is known to have this problem, so skip for non-btrfs */ if (buf.f_type != BTRFS_SUPER_MAGIC) return; if (ioctl(fd, FS_IOC_GETFLAGS, &val) < 0) { fprintf(stderr, "FS_IOC_GET_FLAGS: %s\\n", strerror(errno)); return; } val |= FS_NOCOW_FL; if (ioctl(fd, FS_IOC_SETFLAGS, &val) < 0) fprintf(stderr, "FS_IOC_SET_FLAGS: %s\\n", strerror(errno)); } void nodatacow_dir(const char *dir) { DIR *dh = opendir(dir); int fd; if (!dh) croak("opendir(%s): %s", dir, strerror(errno)); fd = dirfd(dh); if (fd >= 0) nodatacow_fd(fd); /* ENOTSUP probably won't happen under Linux... */ closedir(dh); } SET_NODATACOW my $inline_dir = $ENV{PERL_INLINE_DIRECTORY} //= ( $ENV{XDG_CACHE_HOME} // ( ($ENV{HOME} // '/nonexistent').'/.cache' ) ).'/public-inbox/inline-c'; $set_nodatacow = $vfork_spawn = undef unless -d $inline_dir && -w _; if (defined $vfork_spawn) { # Inline 0.64 or later has locking in multi-process env, # but we support 0.5 on Debian wheezy use Fcntl qw(:flock); eval { my $f = "$inline_dir/.public-inbox.lock"; open my $fh, '>', $f or die "failed to open $f: $!\n"; flock($fh, LOCK_EX) or die "LOCK_EX failed on $f: $!\n"; eval 'use Inline C => $vfork_spawn . $set_nodatacow'; my $err = $@; my $ndc_err; if ($err && $set_nodatacow) { # missing Linux kernel headers $ndc_err = $err; undef $set_nodatacow; eval 'use Inline C => $vfork_spawn'; } flock($fh, LOCK_UN) or die "LOCK_UN failed on $f: $!\n"; die $err if $err; warn $ndc_err if $ndc_err; }; if ($@) { warn "Inline::C failed for vfork: $@\n"; $set_nodatacow = $vfork_spawn = undef; } } unless (defined $vfork_spawn) { require PublicInbox::SpawnPP; *pi_fork_exec = \&PublicInbox::SpawnPP::pi_fork_exec } unless ($set_nodatacow) { require PublicInbox::NDC_PP; no warnings 'once'; *nodatacow_fd = \&PublicInbox::NDC_PP::nodatacow_fd; *nodatacow_dir = \&PublicInbox::NDC_PP::nodatacow_dir; } undef $set_nodatacow; undef $vfork_spawn; sub which ($) { my ($file) = @_; return $file if index($file, '/') >= 0; foreach my $p (split(':', $ENV{PATH})) { $p .= "/$file"; return $p if -x $p; } undef; } sub spawn ($;$$) { my ($cmd, $env, $opts) = @_; my $f = which($cmd->[0]); defined $f or die "$cmd->[0]: command not found\n"; my @env; $opts ||= {}; my %env = $env ? (%ENV, %$env) : %ENV; while (my ($k, $v) = each %env) { push @env, "$k=$v"; } my $redir = []; for my $child_fd (0..2) { my $parent_fd = $opts->{$child_fd}; if (defined($parent_fd) && $parent_fd !~ /\A[0-9]+\z/) { defined(my $fd = fileno($parent_fd)) or die "$parent_fd not an IO GLOB? $!"; $parent_fd = $fd; } $redir->[$child_fd] = $parent_fd // $child_fd; } my $rlim = []; foreach my $l (@RLIMITS) { defined(my $v = $opts->{$l}) or next; my $r = eval "require BSD::Resource; BSD::Resource::$l();"; unless (defined $r) { warn "$l undefined by BSD::Resource: $@\n"; next; } push @$rlim, $r, @$v; } my $cd = $opts->{'-C'} // ''; # undef => NULL mapping doesn't work? my $pid = pi_fork_exec($redir, $f, $cmd, \@env, $rlim, $cd); die "fork_exec @$cmd failed: $!\n" unless $pid > 0; $pid; } sub popen_rd { my ($cmd, $env, $opts) = @_; pipe(my ($r, $w)) or die "pipe: $!\n"; $opts ||= {}; $opts->{1} = fileno($w); my $pid = spawn($cmd, $env, $opts); return ($r, $pid) if wantarray; my $ret = gensym; tie *$ret, 'PublicInbox::ProcessPipe', $pid, $r; $ret; } 1;