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filesystem: Paper over fadvise harmless failure on macos #12138

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filesystem: Paper over fadvise harmless failure on macos #12138

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1da615b
filesystem: Paper over fadvise harmless failure on macos
wingo Dec 8, 2025
2245190
An ungainly fix
wingo Dec 15, 2025
4605d10
Update test expectations
wingo Dec 15, 2025
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24 changes: 21 additions & 3 deletions crates/wasi/src/filesystem.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -752,9 +752,27 @@ impl File {
advice: system_interface::fs::Advice,
) -> Result<(), ErrorCode> {
use system_interface::fs::FileIoExt as _;
self.run_blocking(move |f| f.advise(offset, len, advice))
.await?;
Ok(())
let is_emulated_willneed = cfg!(any(target_os = "macos", target_os = "ios"))
&& advice == system_interface::fs::Advice::WillNeed;
match self
.run_blocking(move |f| f.advise(offset, len, advice))
.await
{
Err(err) => {
let code: ErrorCode = err.into();

// Paper over a difference in behavior; we implement
// MADV_WILLNEED on macos via the F_RDADVISE fnctl,
// which errors on out-of-bounds ranges whereas POSIX
// silently succeeds.
if is_emulated_willneed && matches!(code, ErrorCode::FileTooLarge) {
return Ok(());
}

Err(code)
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@wingo wingo Dec 15, 2025

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I find this patch to be pretty gross, for a few reasons:

  • advice doesn't implement copy, so it gets moved into the closure; have to check it beforehand, making it less amenable to #[cfg]
  • the whole system error vs errorcode thing; can't match on FileTooLarge directly, only on err.into()
  • ErrorCode doesn't implement PartialEq, so no ==

Any style tips are very welcome.

}
Ok(()) => Ok(()),
}
}

pub(crate) async fn set_size(&self, size: u64) -> Result<(), ErrorCode> {
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2 changes: 0 additions & 2 deletions tests/wasi.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,8 +20,6 @@ const KNOWN_FAILURES: &[&str] = &[
"filesystem-read-directory",
// FIXME(#11524)
"remove_directory_trailing_slashes",
#[cfg(target_vendor = "apple")]
"filesystem-advise",
// FIXME(WebAssembly/wasi-testsuite#128)
#[cfg(windows)]
"fd_fdstat_set_rights",
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