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Adds Linux support for POSIX file locking with fcntl

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On Linux, locking fails with EAGAIN (vs. EACCES on other systems).
This commit also adds FcntlErrors for EDEADLK and ENOLCK.
This commit is contained in:
Anthony Carrico 2021-09-25 17:32:18 -04:00 committed by Veikka Tuominen
parent c6cd919a18
commit 078aa5f7b2
17 changed files with 150 additions and 73 deletions
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10
lib/std/c/darwin.zig
View File

@ -357,11 +357,11 @@ pub const off_t = i64;
pub const ino_t = u64;
pub const Flock = extern struct {
l_start: off_t,
l_len: off_t,
l_pid: pid_t,
l_type: i16,
l_whence: i16,
start: off_t,
len: off_t,
pid: pid_t,
type: i16,
whence: i16,
};
pub const Stat = extern struct {

10
lib/std/c/dragonfly.zig
View File

@ -929,11 +929,11 @@ pub const LOCK = struct {
};
pub const Flock = extern struct {
l_start: off_t,
l_len: off_t,
l_pid: pid_t,
l_type: c_short,
l_whence: c_short,
start: off_t,
len: off_t,
pid: pid_t,
type: c_short,
whence: c_short,
};
pub const addrinfo = extern struct {

12
lib/std/c/freebsd.zig
View File

@ -193,12 +193,12 @@ pub const dl_phdr_info = extern struct {
};
pub const Flock = extern struct {
l_start: off_t,
l_len: off_t,
l_pid: pid_t,
l_type: i16,
l_whence: i16,
l_sysid: i32,
start: off_t,
len: off_t,
pid: pid_t,
type: i16,
whence: i16,
sysid: i32,
__unused: [4]u8,
};

10
lib/std/c/haiku.zig
View File

@ -159,11 +159,11 @@ pub const dl_phdr_info = extern struct {
};
pub const Flock = extern struct {
l_type: c_short,
l_whence: c_short,
l_start: off_t,
l_len: off_t,
l_pid: pid_t,
type: c_short,
whence: c_short,
start: off_t,
len: off_t,
pid: pid_t,
};
pub const msghdr = extern struct {

10
lib/std/c/netbsd.zig
View File

@ -169,11 +169,11 @@ pub const dl_phdr_info = extern struct {
};
pub const Flock = extern struct {
l_start: off_t,
l_len: off_t,
l_pid: pid_t,
l_type: i16,
l_whence: i16,
start: off_t,
len: off_t,
pid: pid_t,
type: i16,
whence: i16,
};
pub const addrinfo = extern struct {

10
lib/std/c/openbsd.zig
View File

@ -94,11 +94,11 @@ pub const dl_phdr_info = extern struct {
};
pub const Flock = extern struct {
l_start: off_t,
l_len: off_t,
l_pid: pid_t,
l_type: c_short,
l_whence: c_short,
start: off_t,
len: off_t,
pid: pid_t,
type: c_short,
whence: c_short,
};
pub const addrinfo = extern struct {

12
lib/std/c/solaris.zig
View File

@ -116,13 +116,13 @@ pub const RTLD = struct {
};
pub const Flock = extern struct {
l_type: c_short,
l_whence: c_short,
l_start: off_t,
type: c_short,
whence: c_short,
start: off_t,
// len == 0 means until end of file.
l_len: off_t,
l_sysid: c_int,
l_pid: pid_t,
len: off_t,
sysid: c_int,
pid: pid_t,
__pad: [4]c_long,
};

8
lib/std/fs.zig
View File

@ -1045,6 +1045,8 @@ pub const Dir = struct {
error.FileBusy => unreachable,
error.Locked => unreachable,
error.PermissionDenied => unreachable,
error.DeadLock => unreachable,
error.LockedRegionLimitExceeded => unreachable,
else => |e| return e,
};
fl_flags &= ~@as(usize, os.O.NONBLOCK);
@ -1052,6 +1054,8 @@ pub const Dir = struct {
error.FileBusy => unreachable,
error.Locked => unreachable,
error.PermissionDenied => unreachable,
error.DeadLock => unreachable,
error.LockedRegionLimitExceeded => unreachable,
else => |e| return e,
};
}
@ -1197,6 +1201,8 @@ pub const Dir = struct {
error.FileBusy => unreachable,
error.Locked => unreachable,
error.PermissionDenied => unreachable,
error.DeadLock => unreachable,
error.LockedRegionLimitExceeded => unreachable,
else => |e| return e,
};
fl_flags &= ~@as(usize, os.O.NONBLOCK);
@ -1204,6 +1210,8 @@ pub const Dir = struct {
error.FileBusy => unreachable,
error.Locked => unreachable,
error.PermissionDenied => unreachable,
error.DeadLock => unreachable,
error.LockedRegionLimitExceeded => unreachable,
else => |e| return e,
};
}

14
lib/std/os.zig
View File

@ -4513,6 +4513,8 @@ pub const FcntlError = error{
FileBusy,
ProcessFdQuotaExceeded,
Locked,
DeadLock,
LockedRegionLimitExceeded,
} || UnexpectedError;
pub fn fcntl(fd: fd_t, cmd: i32, arg: usize) FcntlError!usize {
@ -4521,13 +4523,15 @@ pub fn fcntl(fd: fd_t, cmd: i32, arg: usize) FcntlError!usize {
switch (errno(rc)) {
.SUCCESS => return @intCast(usize, rc),
.INTR => continue,
.ACCES => return error.Locked,
.AGAIN, .ACCES => return error.Locked,
.BADF => unreachable,
.BUSY => return error.FileBusy,
.INVAL => unreachable, // invalid parameters
.PERM => return error.PermissionDenied,
.MFILE => return error.ProcessFdQuotaExceeded,
.NOTDIR => unreachable, // invalid parameter
.DEADLK => return error.DeadLock,
.NOLCK => return error.LockedRegionLimitExceeded,
else => |err| return unexpectedErrno(err),
}
}
@ -4542,6 +4546,8 @@ fn setSockFlags(sock: socket_t, flags: u32) !void {
error.FileBusy => unreachable,
error.Locked => unreachable,
error.PermissionDenied => unreachable,
error.DeadLock => unreachable,
error.LockedRegionLimitExceeded => unreachable,
else => |e| return e,
};
fd_flags |= FD_CLOEXEC;
@ -4549,6 +4555,8 @@ fn setSockFlags(sock: socket_t, flags: u32) !void {
error.FileBusy => unreachable,
error.Locked => unreachable,
error.PermissionDenied => unreachable,
error.DeadLock => unreachable,
error.LockedRegionLimitExceeded => unreachable,
else => |e| return e,
};
}
@ -4570,6 +4578,8 @@ fn setSockFlags(sock: socket_t, flags: u32) !void {
error.FileBusy => unreachable,
error.Locked => unreachable,
error.PermissionDenied => unreachable,
error.DeadLock => unreachable,
error.LockedRegionLimitExceeded => unreachable,
else => |e| return e,
};
fl_flags |= O.NONBLOCK;
@ -4577,6 +4587,8 @@ fn setSockFlags(sock: socket_t, flags: u32) !void {
error.FileBusy => unreachable,
error.Locked => unreachable,
error.PermissionDenied => unreachable,
error.DeadLock => unreachable,
error.LockedRegionLimitExceeded => unreachable,
else => |e| return e,
};
}

10
lib/std/os/linux/arm-eabi.zig
View File

@ -638,12 +638,12 @@ pub const HWCAP = struct {
};
pub const Flock = extern struct {
l_type: i16,
l_whence: i16,
type: i16,
whence: i16,
__pad0: [4]u8,
l_start: off_t,
l_len: off_t,
l_pid: pid_t,
start: off_t,
len: off_t,
pid: pid_t,
__unused: [4]u8,
};

10
lib/std/os/linux/arm64.zig
View File

@ -490,11 +490,11 @@ pub const VDSO = struct {
};
pub const Flock = extern struct {
l_type: i16,
l_whence: i16,
l_start: off_t,
l_len: off_t,
l_pid: pid_t,
type: i16,
whence: i16,
start: off_t,
len: off_t,
pid: pid_t,
__unused: [4]u8,
};

10
lib/std/os/linux/mips.zig
View File

@ -707,12 +707,12 @@ pub const VDSO = struct {
};
pub const Flock = extern struct {
l_type: i16,
l_whence: i16,
type: i16,
whence: i16,
__pad0: [4]u8,
l_start: off_t,
l_len: off_t,
l_pid: pid_t,
start: off_t,
len: off_t,
pid: pid_t,
__unused: [4]u8,
};

10
lib/std/os/linux/powerpc.zig
View File

@ -643,11 +643,11 @@ pub const VDSO = struct {
};
pub const Flock = extern struct {
l_type: i16,
l_whence: i16,
l_start: off_t,
l_len: off_t,
l_pid: pid_t,
type: i16,
whence: i16,
start: off_t,
len: off_t,
pid: pid_t,
};
pub const msghdr = extern struct {

10
lib/std/os/linux/powerpc64.zig
View File

@ -617,11 +617,11 @@ pub const VDSO = struct {
};
pub const Flock = extern struct {
l_type: i16,
l_whence: i16,
l_start: off_t,
l_len: off_t,
l_pid: pid_t,
type: i16,
whence: i16,
start: off_t,
len: off_t,
pid: pid_t,
__unused: [4]u8,
};

10
lib/std/os/linux/riscv64.zig
View File

@ -480,11 +480,11 @@ pub const timeval = extern struct {
};
pub const Flock = extern struct {
l_type: i16,
l_whence: i16,
l_start: off_t,
l_len: off_t,
l_pid: pid_t,
type: i16,
whence: i16,
start: off_t,
len: off_t,
pid: pid_t,
__unused: [4]u8,
};

10
lib/std/os/linux/sparc64.zig
View File

@ -648,11 +648,11 @@ pub const VDSO = struct {
};
pub const Flock = extern struct {
l_type: i16,
l_whence: i16,
l_start: off_t,
l_len: off_t,
l_pid: pid_t,
type: i16,
whence: i16,
start: off_t,
len: off_t,
pid: pid_t,
};
pub const msghdr = extern struct {

57
lib/std/os/test.zig
View File

@ -821,3 +821,60 @@ test "writev longer than IOV_MAX" {
const amt = try file.writev(&iovecs);
try testing.expectEqual(@as(usize, os.IOV_MAX), amt);
}
test "POSIX file locking with fcntl" {
if (native_os == .windows or native_os == .wasi) return error.SkipZigTest;
var tmp = std.testing.tmpDir(.{});
defer tmp.cleanup();
// Create a temporary lock file
var file = try tmp.dir.createFile("lock", .{ .read = true });
defer file.close();
try file.setEndPos(2);
const fd = file.handle;
// Place an exclusive lock on the first byte, and a shared lock on the second byte:
var struct_flock = std.mem.zeroInit(std.os.Flock, .{ .type = std.os.F.WRLCK });
_ = try std.os.fcntl(fd, std.os.F.SETLK, @ptrToInt(&struct_flock));
struct_flock.start = 1;
struct_flock.type = std.os.F.RDLCK;
_ = try std.os.fcntl(fd, std.os.F.SETLK, @ptrToInt(&struct_flock));
// Check the locks in a child process:
const pid = try std.os.fork();
if (pid == 0) {
// child expects be denied the exclusive lock:
struct_flock.start = 0;
struct_flock.type = std.os.F.WRLCK;
try expectError(error.Locked, std.os.fcntl(fd, std.os.F.SETLK, @ptrToInt(&struct_flock)));
// child expects to get the shared lock:
struct_flock.start = 1;
struct_flock.type = std.os.F.RDLCK;
_ = try std.os.fcntl(fd, std.os.F.SETLK, @ptrToInt(&struct_flock));
// child waits for the exclusive lock in order to test deadlock:
struct_flock.start = 0;
struct_flock.type = std.os.F.WRLCK;
_ = try std.os.fcntl(fd, std.os.F.SETLKW, @ptrToInt(&struct_flock));
// child exits without continuing:
std.os.exit(0);
} else {
// parent waits for child to get shared lock:
std.time.sleep(1 * std.time.ns_per_ms);
// parent expects deadlock when attempting to upgrade the shared lock to exclusive:
struct_flock.start = 1;
struct_flock.type = std.os.F.WRLCK;
try expectError(error.DeadLock, std.os.fcntl(fd, std.os.F.SETLKW, @ptrToInt(&struct_flock)));
// parent releases exclusive lock:
struct_flock.start = 0;
struct_flock.type = std.os.F.UNLCK;
_ = try std.os.fcntl(fd, std.os.F.SETLK, @ptrToInt(&struct_flock));
// parent releases shared lock:
struct_flock.start = 1;
struct_flock.type = std.os.F.UNLCK;
_ = try std.os.fcntl(fd, std.os.F.SETLK, @ptrToInt(&struct_flock));
// parent waits for child:
const result = std.os.waitpid(pid, 0);
try expect(result.status == 0 * 256);
}
}