JDK-8030048: (fs) Support UserDefinedFileAttributeView/extended attributes on OS X / HFS+

[overheadhunter]

This adds support for UserDefinedFileAttributeView on macOS 10.4 and newer.

While the main audience for this will probably be macOS users, the relevant changes take place in (mostly existing) classes carrying BSD in their names as none of this is really macOS-specific.

Code is mostly copied from the Linux implementation except for three differences:

1. max length for attribute names is 127 bytes
2. we know for sure that APFS and HFS+ support extended attributes, therefore we simply return true from supportsFileAttributeView(UserDefinedFileAttributeView.class) for these two FS types, while for all other types support is determined experimentally in isExtendedAttributesEnabled(...)
3. For the aforementioned check the new UnixConstants.ENOATTR is added, which seems to be macOS and BSD-specific.

As discussed in the mailing list, for ease of tracking changes it is not a goal of this patch to modernize the existing Linux implementation, nor to deduplicate anything.

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change must be properly reviewed

Issue

• JDK-8030048: (fs) Support UserDefinedFileAttributeView/extended attributes on OS X / HFS+

Reviewers

• Alan Bateman (@AlanBateman - Reviewer)

Download

$ git fetch https://git.openjdk.java.net/jdk pull/2017/head:pull/2017
$ git checkout pull/2017

[bridgekeeper]

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[openjdk]

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[overheadhunter]

/covered This patch is submitted on behalf of Skymatic GmbH, for whom I've recently sent in the signed OCA.

[overheadhunter]

/covered

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[mlbridge]

Webrevs

• 03: Full - Incremental (9258c37)
• 02: Full - Incremental (bcd206c)
• 01: Full - Incremental (5d00aa6)
• 00: Full (7a3619d)

[AlanBateman]

Overall, this looks quite good and is easy to review.

I think the additions to BsdNativeDispatcher. will need a round or two of cleanup. They comments about XATTR_NOFOLLOW and other options documented in the man pages are a bit distracting. Also the style and excessive long lines aren't consistent with the existing code (and UnixNativeDispatcher).

One thing that we need to decide is whether the additional parameters (position, options) are exposed by BsdNativeDispatcher or not. I think I agree with your approach to have the signature match the methods in LinuxNativeDispatcher as that will make it easier to merge the two implementations later.

The comments that XATTR_NOFOLLOW is not applicable and other options not used is distracting and can be removed.

[overheadhunter]

One thing that we need to decide is whether the additional parameters (position, options) are exposed by BsdNativeDispatcher or not. I think I agree with your approach to have the signature match the methods in LinuxNativeDispatcher as that will make it easier to merge the two implementations later.

Just to discuss all options, we could as well hide both params from Java entirely (set them inside of BsdNativeDispatcher.c)

The comments that XATTR_NOFOLLOW is not applicable and other options not used is distracting and can be removed.

Sure, but maybe it should be documented somewhere that none of the flags are required for this use case? Or do you think it is reasonable to assume that anyone stumbling upon this code will just look up the system calls' documentation to see what flags might have been possible?

[AlanBateman]

Thanks for the updates. I can sponsor once, you'll need to enter "/integrate"

[openjdk]

@overheadhunter This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8030048: (fs) Support UserDefinedFileAttributeView/extended attributes on OS X / HFS+

Reviewed-by: alanb

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 147 new commits pushed to the master branch:

• d7d34dd: 8259799: vmTestbase/nsk/jvmti/Breakpoint/breakpoint001 is incorrect
• fe84ecd: 8259048: (tz) Upgrade time-zone data to tzdata2020f
• 9aa5672: 8259068: Streamline class loader locking
• 27a39c8: 8193031: Collections.addAll is likely to perform worse than Collection.addAll
• 5855d52: 8259651: [macOS] Replace JNF_COCOA_ENTER/EXIT macros
• 360c722: 8259729: Missed JNFInstanceOf -> IsInstanceOf conversion
• b78cd63: 8259846: [BACKOUT] JDK-8259278 Optimize Vector API slice and unslice operations
• eb7fa00: 8259216: javadoc omits method receiver for any nested type annotation
• bcf20a0: 8259777: Incorrect predication condition generated by ADLC
• bbac91a: 8257959: Add gtest run with -XX:+UseLargePages
• ... and 137 more: https://git.openjdk.java.net/jdk/compare/712014c5956cf74982531d212b03460843e4e5b6...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@AlanBateman) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

[overheadhunter]

/integrate

[openjdk]

@overheadhunter
Your change (at version 9258c37) is now ready to be sponsored by a Committer.

[mlbridge]

Mailing list message from Sebastian Stenzel on nio-dev:

Thank you, Alan, for guiding me through the process and reviewing the changes!

Regarding the deduplication I already have some ideas and questions, but I think I'll do this in a new thread in a couple of days.

[AlanBateman]

/integrate

[openjdk]

@AlanBateman Only the author (@overheadhunter) is allowed to issue the integrate command. As this PR is ready to be sponsored, and you are an eligible sponsor, did you mean to issue the /sponsor command?

[AlanBateman]

/sponsor

[openjdk]

@AlanBateman @overheadhunter Since your change was applied there have been 152 commits pushed to the master branch:

• bbb93ca: 8256126: Create implementation for NSAccessibilityImage protocol peer
• 90c73d0: 8259569: gtest os.dll_address_to_function_and_library_name_vm fails
• 536082d: Merge
• e85892b: 8258396: SIGILL in jdk.jfr.internal.PlatformRecorder.rotateDisk()
• d63388c: 8259266: com/sun/jdi/JdbOptions.java failed with "RuntimeException: 'prop[boo] = >foo 2<' missing from stdout/stderr"
• d7d34dd: 8259799: vmTestbase/nsk/jvmti/Breakpoint/breakpoint001 is incorrect
• fe84ecd: 8259048: (tz) Upgrade time-zone data to tzdata2020f
• 9aa5672: 8259068: Streamline class loader locking
• 27a39c8: 8193031: Collections.addAll is likely to perform worse than Collection.addAll
• 5855d52: 8259651: [macOS] Replace JNF_COCOA_ENTER/EXIT macros
• ... and 142 more: https://git.openjdk.java.net/jdk/compare/712014c5956cf74982531d212b03460843e4e5b6...master

Your commit was automatically rebased without conflicts.

Pushed as commit afd3f78.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

[mlbridge]

Mailing list message from Alan Bateman on nio-dev:

On 15/01/2021 20:19, Sebastian Stenzel wrote:

:
Thank you, Alan, for guiding me through the process and reviewing the changes!

Regarding the deduplication I already have some ideas and questions, but I think I'll do this in a new thread in a couple of days.

No problem, it's a good contribution for something that the maintainers
in this area never got time to work on.

One issue is that has come up since the commit is that
UserDefinedFileAttributeView/Basic.java is failing on macOS 10.13
systems. I've created JDK-8259865 [1] to track it. I can't duplicate it
on 10.14 and 10.15. I think the issue is that fgetxattr is not failing
with -1/ERANGE when the buffer is too small. We may have to disable
support for user defined file attributes on systems older than 10.14.

-Alan

[1] https://bugs.openjdk.java.net/browse/JDK-8259865