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Add MapFlags::map_hugetlb_with_size_log2 #2125

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Nov 14, 2023
Merged

Add MapFlags::map_hugetlb_with_size_log2 #2125

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6fd0d66
Add `MapFlags::map_hugetlb_with_size_log2`
newpavlov Oct 2, 2023
d2785bf
Add changelog
newpavlov Nov 13, 2023
47f5178
Add TODO note
newpavlov Nov 14, 2023
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1 change: 1 addition & 0 deletions changelog/2125.added.md
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@@ -0,0 +1 @@
Added `MapFlags::map_hugetlb_with_size_log2` method for Linux targets
27 changes: 27 additions & 0 deletions src/sys/mman.rs
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Expand Up @@ -190,6 +190,33 @@ libc_bitflags! {
}
}

impl MapFlags {
/// Create `MAP_HUGETLB` with provided size of huge page.
///
/// Under the hood it computes `MAP_HUGETLB | (huge_page_size_log2 << libc::MAP_HUGE_SHIFT`).
/// `huge_page_size_log2` denotes logarithm of huge page size to use and should be
/// between 16 and 63 (inclusively).
///
/// ```
/// # use nix::sys::mman::MapFlags;
/// let f = MapFlags::map_hugetlb_with_size_log2(30).unwrap();
/// assert_eq!(f, MapFlags::MAP_HUGETLB | MapFlags::MAP_HUGE_1GB);
/// ```
// TODO: support Andorid and Fuchsia when https://github.com/rust-lang/libc/pull/3444
// will be released
#[cfg(target_os = "linux")]
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This should probably include android and fuchsia, too. At least, libc defines MAP_HUGETLB for those platforms. But it doesn't define MAP_HUGE_SHIFT. Is that an oversight in libc?

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Is that an oversight in libc?

Maybe. Either way, we would need first introduce the constant to libc and only then add expand list of targets, so I think it's better to do it in a later PR.

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I filed a PR adding these symbols for Android or Linux: rust-lang/libc#3444

#[cfg_attr(docsrs, doc(cfg(all())))]
pub fn map_hugetlb_with_size_log2(huge_page_size_log2: u32) -> Option<Self> {
if (16..=63).contains(&huge_page_size_log2) {
let flag = libc::MAP_HUGETLB
| (huge_page_size_log2 << libc::MAP_HUGE_SHIFT) as i32;
Some(Self(flag.into()))
} else {
None
}
}
}

#[cfg(any(target_os = "linux", target_os = "netbsd"))]
libc_bitflags! {
/// Options for [`mremap`].
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