Merge pull request #6895 from jorangreef/fallocate

linux: add fallocate()

lib/std/c/linux.zig

@@ -87,6 +87,8 @@ pub extern "c" fn sigaltstack(ss: ?*stack_t, old_ss: ?*stack_t) c_int;
 
 pub extern "c" fn memfd_create(name: [*:0]const u8, flags: c_uint) c_int;
 
+pub extern "c" fn fallocate(fd: fd_t, mode: c_int, offset: off_t, len: off_t) c_int;
+
 pub extern "c" fn ftruncate64(fd: c_int, length: off_t) c_int;
 
 pub extern "c" fn sendfile(

lib/std/os/bits/linux.zig

@@ -84,6 +84,27 @@ pub const AT_STATX_DONT_SYNC = 0x4000;
 /// Apply to the entire subtree
 pub const AT_RECURSIVE = 0x8000;
 
+/// Default is extend size
+pub const FALLOC_FL_KEEP_SIZE = 0x01;
+
+/// De-allocates range
+pub const FALLOC_FL_PUNCH_HOLE = 0x02;
+
+/// Reserved codepoint
+pub const FALLOC_FL_NO_HIDE_STALE = 0x04;
+
+/// Removes a range of a file without leaving a hole in the file
+pub const FALLOC_FL_COLLAPSE_RANGE = 0x08;
+
+/// Converts a range of file to zeros preferably without issuing data IO
+pub const FALLOC_FL_ZERO_RANGE = 0x10;
+
+/// Inserts space within the file size without overwriting any existing data
+pub const FALLOC_FL_INSERT_RANGE = 0x20;
+
+/// Unshares shared blocks within the file size without overwriting any existing data
+pub const FALLOC_FL_UNSHARE_RANGE = 0x40;
+
 pub const FUTEX_WAIT = 0;
 pub const FUTEX_WAKE = 1;
 pub const FUTEX_FD = 2;

lib/std/os/linux.zig

@@ -136,6 +136,30 @@ pub fn utimensat(dirfd: i32, path: ?[*:0]const u8, times: *const [2]timespec, fl
     return syscall4(.utimensat, @bitCast(usize, @as(isize, dirfd)), @ptrToInt(path), @ptrToInt(times), flags);
 }
 
+pub fn fallocate(fd: i32, mode: i32, offset: u64, length: u64) usize {
+    if (@sizeOf(usize) == 4) {
+        const offset_halves = splitValue64(offset);
+        const length_halves = splitValue64(length);
+        return syscall6(
+            .fallocate,
+            @bitCast(usize, @as(isize, fd)),
+            @bitCast(usize, @as(isize, mode)),
+            offset_halves[0],
+            offset_halves[1],
+            length_halves[0],
+            length_halves[1],
+        );
+    } else {
+        return syscall4(
+            .fallocate,
+            @bitCast(usize, @as(isize, fd)),
+            @bitCast(usize, @as(isize, mode)),
+            offset,
+            length,
+        );
+    }
+}
+
 pub fn futex_wait(uaddr: *const i32, futex_op: u32, val: i32, timeout: ?*timespec) usize {
     return syscall4(.futex, @ptrToInt(uaddr), futex_op, @bitCast(u32, val), @ptrToInt(timeout));
 }

lib/std/os/linux/test.zig

@@ -11,6 +11,25 @@ const elf = std.elf;
 const expect = std.testing.expect;
 const fs = std.fs;
 
+test "fallocate" {
+    const path = "test_fallocate";
+    const file = try fs.cwd().createFile(path, .{ .truncate = true, .mode = 0o666 });
+    defer file.close();
+    defer fs.cwd().deleteFile(path) catch {};
+
+    expect((try file.stat()).size == 0);
+
+    const len: u64 = 65536;
+    switch (linux.getErrno(linux.fallocate(file.handle, 0, 0, len))) {
+        0 => {},
+        linux.ENOSYS => return error.SkipZigTest,
+        linux.EOPNOTSUPP => return error.SkipZigTest,
+        else => |errno| std.debug.panic("unhandled errno: {}", .{ errno }),
+    }
+
+    expect((try file.stat()).size == len);
+}
+
 test "getpid" {
     expect(linux.getpid() != 0);
 }