From cf47d283d101e5d8e0d1ca7ec427d40efc40f358 Mon Sep 17 00:00:00 2001 From: Pat Tullmann Date: Sat, 19 Jul 2025 09:34:04 -0700 Subject: [PATCH] lib/std/posix/test.zig: don't compare blksize in "fstatat" In trying to reproduce the race in #24380, my system tripped over the stat "blocks" field changing in this test. The value was almost always 8 (effectively 4k) or very infrequently 0 (I saw the 0 from both `fstat` and `fstatat`). I believe the underlying filesystem is free to asynchronously change this value. For example, if it migrates a file between some "inline" or maybe journal storage, and actual on-disk blocks. So it seems plausible that its allowed to change between stat calls. Breaking up the struct comparison this way means we also don't compare any of the padding or "reserved" fields, too. And we can narrow down the s390x-linux work-around. --- lib/std/posix/test.zig | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-) diff --git a/lib/std/posix/test.zig b/lib/std/posix/test.zig index 8199be65aa..55a53518d9 100644 --- a/lib/std/posix/test.zig +++ b/lib/std/posix/test.zig @@ -395,11 +395,27 @@ test "fstatat" { // now repeat but using `fstatat` instead const statat = try posix.fstatat(tmp.dir.fd, "file.txt", posix.AT.SYMLINK_NOFOLLOW); - // s390x-linux does not have nanosecond precision for fstat(), but it does for fstatat(). As a - // result, comparing the two structures is doomed to fail. - if (builtin.cpu.arch == .s390x and builtin.os.tag == .linux) return error.SkipZigTest; + try expectEqual(stat.dev, statat.dev); + try expectEqual(stat.ino, statat.ino); + try expectEqual(stat.nlink, statat.nlink); + try expectEqual(stat.mode, statat.mode); + try expectEqual(stat.uid, statat.uid); + try expectEqual(stat.gid, statat.gid); + try expectEqual(stat.rdev, statat.rdev); + try expectEqual(stat.size, statat.size); + try expectEqual(stat.blksize, statat.blksize); - try expectEqual(stat, statat); + // The stat.blocks/statat.blocks count is managed by the filesystem and may + // change if the file is stored in a journal or "inline". + // try expectEqual(stat.blocks, statat.blocks); + + // s390x-linux does not have nanosecond precision for fstat(), but it does for + // fstatat(). As a result, comparing the timestamps isn't worth the effort + if (!(builtin.cpu.arch == .s390x and builtin.os.tag == .linux)) { + try expectEqual(stat.atime(), statat.atime()); + try expectEqual(stat.mtime(), statat.mtime()); + try expectEqual(stat.ctime(), statat.ctime()); + } } test "readlinkat" {