Add MAP_SHARED_VALIDATE & MAP_SYNC #2499
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This pull adds two flags: MAP_SHARED_VALIDATE & MAP_SYNC implemented on https://github.com/rust-lang/libc The MAP_SHARED_VALIDATE flag was added to linux since 4.15, its a flag that does two things: provide backwards compatibility with old mmap implementations that don't check for flags, and allow new flags to be added. MAP_SYNC, on the other hand, was added to allow mmap to utilize Direct Accses (DAX) on hardware that support it (non-volatile memory devices) or in general: any ram-shaped filesystem. both flags are available on both linux and android.
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I was using a local fork of nix that had these updates. Didn't realize I didn't create a branch for this pull request and it's very cluttered, @SteveLauC, I'm thinking we can close this PR and I'll create a new one? |
src/sys/mman.rs
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| /// Force mmap to check and fail on unknown flags. This also enables `MAP_SYNC`. | ||
| #[cfg(all(any(target_arch = "x86"), not(linux_android), not(target_os = "hurd"), not(target_env = "uclibc"), not(freebsdlike)))] |
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| /// Force mmap to check and fail on unknown flags. This also enables `MAP_SYNC`. | |
| #[cfg(all(any(target_arch = "x86"), not(linux_android), not(target_os = "hurd"), not(target_env = "uclibc"), not(freebsdlike)))] | |
| /// Force mmap to check and fail on unknown flags. This also enables `MAP_SYNC`. | |
| #[cfg(target_os = "linux")] |
This flag is available on all the Linux targets.
src/sys/mman.rs
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| /// Do not write through the page caches, write directly to the file. Used for Direct Access (DAX) enabled file systems. | ||
| #[cfg(all(any(target_arch = "x86"), not(linux_android), not(target_os = "hurd"), not(target_env = "uclibc"), not(freebsdlike)))] |
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This flag is not that lucky, uClibc does not have it, for the glibc and musl, seems that they all lack the support for the MIPS target, so this should work for now:
| /// Do not write through the page caches, write directly to the file. Used for Direct Access (DAX) enabled file systems. | |
| #[cfg(all(any(target_arch = "x86"), not(linux_android), not(target_os = "hurd"), not(target_env = "uclibc"), not(freebsdlike)))] | |
| /// Do not write through the page caches, write directly to the file. Used for Direct Access (DAX) enabled file systems. | |
| // Available on Linux glibc and musl, MIPS* target excluded. | |
| #[cfg(all(target_os = "linux", not(any(target_arch = "mips", target_arch = "mips64", target_arch = "mipsel", target_arch = "mips64el")), not(target_env = "uclibc")))] |
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That's great, thanks for the suggestions and apologies again for all the clutter
changelog/2499.added.md
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| @@ -0,0 +1 @@ | |||
| Added `MAP_SHARED_VALIDATE` & `MAP_SYNC` for x86. | |||
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When you apply the suggested changes, changelog should also be updated:)
You can, of course. But the current PR looks not bad👀 |
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They've all passed! again thanks for the CI magic! @SteveLauC |
This pull adds two flags: MAP_SHARED_VALIDATE & MAP_SYNC implemented on https://github.com/rust-lang/libc
The MAP_SHARED_VALIDATE flag was added to linux since 4.15, its a flag that does two things: provide backwards compatibility with old mmap implementations that don't check for unknown flags, and allow new flags to be added.
MAP_SYNC, on the other hand, was added to allow mmap to utilize Direct Accses (DAX) on hardware that support it (non-volatile memory devices) or in general: any ram-shaped filesystem.
both flags are available on both linux and android. (Edit: The android kernel does not support the flags)
Notice:
mmap always returns ENOTSUPP when MAP_SYNC is used on filesystems that are not mounted with DAX enabled (normal everyday filesystems), this means that this kind of test would not be possible on github CI.
What does this PR do
Checklist:
CONTRIBUTING.md