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std: Make file copy ops use zero-copy mechanisms 

Use copy_file_range on Linux (if available), fcopyfile on Darwin,
sendfile on *BSDs (and on Linux kernels without copy_file_range).
master
LemonBoy 2020-10-03 12:31:17 +02:00
parent b358c28171
commit 0f248e0988
3 changed files with 102 additions and 11 deletions
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10
lib/std/c/darwin.zig
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@ -18,6 +18,16 @@ pub extern "c" fn _dyld_get_image_header(image_index: u32) ?*mach_header;
pub extern "c" fn _dyld_get_image_vmaddr_slide(image_index: u32) usize;
pub extern "c" fn _dyld_get_image_name(image_index: u32) [*:0]const u8;
pub const COPYFILE_ACL = 1 << 0;
pub const COPYFILE_STAT = 1 << 1;
pub const COPYFILE_XATTR = 1 << 2;
pub const COPYFILE_DATA = 1 << 3;
pub const copyfile_state_t = *@Type(.Opaque);
pub extern "c" fn copyfile_state_alloc() copyfile_state_t;
pub extern "c" fn copyfile_state_free(state: copyfile_state_t) c_int;
pub extern "c" fn fcopyfile(from: fd_t, to: fd_t, state: ?copyfile_state_t, flags: u32) c_int;
pub extern "c" fn @"realpath$DARWIN_EXTSN"(noalias file_name: [*:0]const u8, noalias resolved_name: [*]u8) ?[*:0]u8;
pub extern "c" fn __getdirentries64(fd: c_int, buf_ptr: [*]u8, buf_len: usize, basep: *i64) isize;

2
lib/std/fs.zig
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@ -1823,7 +1823,7 @@ pub const Dir = struct {
var atomic_file = try dest_dir.atomicFile(dest_path, .{ .mode = mode });
defer atomic_file.deinit();
try atomic_file.file.writeFileAll(in_file, .{ .in_len = size });
try os.copy_file(in_file.handle, atomic_file.file.handle, .{ .file_size = size });
return atomic_file.finish();
}

101
lib/std/os.zig
View File

@ -4981,19 +4981,15 @@ pub const CopyFileRangeError = error{
pub fn copy_file_range(fd_in: fd_t, off_in: u64, fd_out: fd_t, off_out: u64, len: usize, flags: u32) CopyFileRangeError!usize {
const use_c = std.c.versionCheck(.{ .major = 2, .minor = 27, .patch = 0 }).ok;
// TODO support for other systems than linux
const try_syscall = comptime std.Target.current.os.isAtLeast(.linux, .{ .major = 4, .minor = 5 }) != false;
if (use_c or try_syscall) {
if (std.Target.current.os.tag == .linux and
(use_c or has_copy_file_range_syscall.get() != 0))
{
const sys = if (use_c) std.c else linux;
var off_in_copy = @bitCast(i64, off_in);
var off_out_copy = @bitCast(i64, off_out);
const rc = sys.copy_file_range(fd_in, &off_in_copy, fd_out, &off_out_copy, len, flags);
// TODO avoid wasting a syscall every time if kernel is too old and returns ENOSYS https://github.com/ziglang/zig/issues/1018
switch (sys.getErrno(rc)) {
0 => return @intCast(usize, rc),
EBADF => unreachable,
@ -5005,9 +5001,14 @@ pub fn copy_file_range(fd_in: fd_t, off_in: u64, fd_out: fd_t, off_out: u64, len
EOVERFLOW => return error.Unseekable,
EPERM => return error.PermissionDenied,
ETXTBSY => return error.FileBusy,
EINVAL => {}, // these may not be regular files, try fallback
EXDEV => {}, // support for cross-filesystem copy added in Linux 5.3, use fallback
ENOSYS => {}, // syscall added in Linux 4.5, use fallback
// these may not be regular files, try fallback
EINVAL => {},
// support for cross-filesystem copy added in Linux 5.3, use fallback
EXDEV => {},
// syscall added in Linux 4.5, use fallback
ENOSYS => {
has_copy_file_range_syscall.set(0);
},
else => |err| return unexpectedErrno(err),
}
}
@ -5021,6 +5022,86 @@ pub fn copy_file_range(fd_in: fd_t, off_in: u64, fd_out: fd_t, off_out: u64, len
return pwrite(fd_out, buf[0..amt_read], off_out);
}
var has_copy_file_range_syscall = std.atomic.Int(u1).init(1);
pub const CopyFileOptions = struct {
/// Size in bytes of the source files, if available saves a call to stat().
file_size: ?u64 = null,
};
pub const CopyFileError = error{
SystemResources,
FileTooBig,
InputOutput,
IsDir,
OutOfMemory,
NoSpaceLeft,
Unseekable,
PermissionDenied,
FileBusy,
} || FStatError || SendFileError;
/// Transfer all the data between two file descriptors in the most efficient way.
/// No metadata is transferred over.
pub fn copy_file(fd_in: fd_t, fd_out: fd_t, options: CopyFileOptions) CopyFileError!void {
if (comptime std.Target.current.isDarwin()) {
const rc = system.fcopyfile(fd_in, fd_out, null, system.COPYFILE_DATA);
switch (errno(rc)) {
0 => return,
EINVAL => unreachable,
ENOMEM => return error.SystemResources,
// The source file was not a directory, symbolic link, or regular file.
// Try with the fallback path before giving up.
ENOTSUP => {},
else => |err| return unexpectedErrno(err),
}
}
const src_file_size = options.file_size orelse
@bitCast(u64, (try fstat(fd_in)).size);
var remaining = src_file_size;
if (std.Target.current.os.tag == .linux) {
// Try copy_file_range first as that works at the FS level and is the
// most efficient method (if available).
if (has_copy_file_range_syscall.get() != 0) {
cfr_loop: while (remaining > 0) {
const copy_amt = math.cast(usize, remaining) catch math.maxInt(usize);
const rc = linux.copy_file_range(fd_in, null, fd_out, null, copy_amt, 0);
switch (errno(rc)) {
0 => {},
EBADF => unreachable,
EFBIG => return error.FileTooBig,
EIO => return error.InputOutput,
EISDIR => return error.IsDir,
ENOMEM => return error.OutOfMemory,
ENOSPC => return error.NoSpaceLeft,
EOVERFLOW => return error.Unseekable,
EPERM => return error.PermissionDenied,
ETXTBSY => return error.FileBusy,
// these may not be regular files, try fallback
EINVAL => break :cfr_loop,
// support for cross-filesystem copy added in Linux 5.3, use fallback
EXDEV => break :cfr_loop,
// syscall added in Linux 4.5, use fallback
ENOSYS => {
has_copy_file_range_syscall.set(0);
break :cfr_loop;
},
else => |err| return unexpectedErrno(err),
}
remaining -= rc;
}
return;
}
}
// Sendfile is a zero-copy mechanism iff the OS supports it, otherwise the
// fallback code will copy the contents chunk by chunk.
const empty_iovec = [0]iovec_const{};
_ = try sendfile(fd_out, fd_in, 0, remaining, &empty_iovec, &empty_iovec, 0);
}
pub const PollError = error{
/// The kernel had no space to allocate file descriptor tables.
SystemResources,