Report a file system's block size and space, as statvfs gives them - #42

This PR implements file system block size and space reporting via statvfs, fixing FileStore and File space methods that previously returned 0, and enabling direct I/O alignment. The VFS backend interface adds an optional space() method; NodeBackend implements it with fs.statfsSync. UnixNativeDispatcher.statvfs0 and UnixFileSystem.getSpace0 now populate UnixFileStoreAttributes and return block-size-scaled totals. setDirect0 returns the block size for direct buffer alignment. New test FileStores.java and four directio tests pass.

_{review-bot, model nvidia/nemotron-3-ultra-550b-a55b:free, verdict approve}

This PR implements statvfs support to report file system block size and space. Previously statvfs0 and getSpace0 were stubs returning 0, causing FileStore and File space methods to return 0 and direct I/O to fail with negative alignment. The changes add a Space interface, implement space() in VFS (defaulting to 4KB blocks for virtual file systems) and NodeBackend (using fs.statfsSync), wire up getSpace0 and statvfs0 natives to return block size and block counts, and make setDirect0 return the block size for direct I/O alignment. Four directio tests now pass and a new FileStores.java test validates the behavior. InterruptCopy.java is removed from passing tests because it requires 2GB usable space which exceeds CI's memory limit when java-web buffers files in memory.

_{review-bot, model nvidia/nemotron-3-ultra-550b-a55b:free, verdict approve}

The PR implements statvfs support so FileStore and File report real block size and space instead of zeros. A Space interface and optional Backend.space are added; VFS provides a 4 KB / zero-space fallback for virtual file systems. NodeBackend.space reads host figures via fs.statfsSync. UnixNativeDispatcher.statvfs0 and UnixFileSystem.getSpace0 now fill attributes and return block-size multiples, and setDirect0 returns the block size for direct I/O alignment. The four directio tests now pass and are added to passing.txt; InterruptCopy.java is removed because it now tries to copy a 1 GB file and exceeds CI memory. All typecheck and test runs pass.

_{review-bot, model nvidia/nemotron-3-ultra-550b-a55b:free, verdict approve}

This PR implements statvfs support so that FileStore reports the host file system's block size and space (total, free, usable) instead of zeros, and direct I/O gets the correct alignment. A Space interface is added to the VFS backend contract; NodeBackend implements it via fs.statfsSync, while other backends fall back to 4 KB blocks and no space. UnixNativeDispatcher.statvfs0 and UnixFileSystem.getSpace0 are wired to the new data, and UnixFileDispatcherImpl.setDirect0 returns the block size for direct I/O alignment. The four directio tests now pass and are added to passing.txt; InterruptCopy.java is removed because it needs 2 GB usable space and java-web buffers files in memory.

_{review-bot, model nvidia/nemotron-3-ultra-550b-a55b:free, verdict approve}

This PR implements file system block size and space reporting via statvfs. Previously statvfs0 and getSpace0 were stubs returning 0, causing FileStore and File space methods to return 0 and direct I/O to fail with negative buffer capacity. The change adds a Space interface, implements space() in VFS (defaulting to 4 KB blocks and no space for virtual file systems) and NodeBackend (using fs.statfsSync), wires getSpace0, statvfs0, and setDirect0 to use these values, and adds a test verifying block size, totals, missing-file behavior, and aligned direct buffers. Four direct I/O tests now pass; InterruptCopy.java is removed from the passing list because it requires 2 GB usable space and java-web buffers files in memory.

_{review-bot, model nvidia/nemotron-3-ultra-550b-a55b:free, verdict approve}

Actionable comments posted: 1

Additional comments: 1

src/node.ts-154-155: 1

154-155: Major · Stability & Availability · Heavy lift

Unverified finding
Verification ran but could not confirm this finding. It is shown for review, not as a verified issue.

Support large files before advertising host space.

A caller can now see enough usable space to start a large operation, while open files remain buffered in memory. The pinned JDK’s InterruptCopy test takes this path when it sees 2 GiB free and creates a 1 GiB file. The PR reports that this exceeds the CI memory limit. Reopening that file also exceeds NodeBackend.read’s 512 MiB limit. Use bounded, host-backed file I/O so space checks do not enable operations the VFS cannot complete. (raw.githubusercontent.com)

As per coding guidelines: “Small and memory efficient. It should run on low-end devices.”

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Inline comments:
Review comments at @src/natives/nio.ts:
- Line 454: Update setDirect0 to read the block size from the open file’s
filesystem path, falling back to its retained detached path when unlinking has
cleared the active path; preserve the existing behavior when the active path is
present.

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Files selected for processing: 6

• src/fs.ts
• src/natives/io.ts
• src/natives/nio.ts
• src/node.ts
• test/java/FileStores.java
• test/jtreg/passing.txt

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Files:

• src/natives/io.ts
• test/jtreg/passing.txt
• src/natives/nio.ts
• src/fs.ts
• test/java/FileStores.java
• src/node.ts

ast-grep (0.51.1)

test/java/FileStores.java

[warning] 16-16: Prevent path traversal
Context: new File(tmp.toFile(), "no-such-file")
Note: [CWE-22] Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'). Security best practice.

(path-traversal-java)

This PR implements file system space reporting via statvfs and direct I/O support. It adds a Space interface to the VFS, implements statvfs0 and getSpace0 natives to return block size and space figures from the host (NodeBackend uses fs.statfsSync), and makes setDirect0 return the block size for direct I/O alignment. Virtual file systems default to 4 KB blocks with zero space. Four directio tests now pass; InterruptCopy.java is removed from passing.txt because it requires 2 GB usable space which java-web cannot provide in-memory.

_{review-bot, model nvidia/nemotron-3-ultra-550b-a55b:free, verdict approve}