Bug fixes

• Rapid Bucket Startup Optimization: Accelerated startup for Rapid buckets by skipping redundant DirectPath connectivity checks [PR#5027]

Bug fixes & Improvements:

• Stat Cache Bug Fix: Addressed a bug where windowed listing operations incorrectly added negative entries to the stat cache in rare scenarios, resulting in erroneous ENOENT (File Not Found) responses for implicit directories [PR#5025].
• Mount Optimization: Disabled internal Go SDK retries for DirectPath connectivity verification to prevent mounting from getting stalled during transient network issues[PR#4993].
• Rapid Bucket Startup Optimization: Accelerated startup for Rapid buckets by skipping redundant DirectPath connectivity checks [PR#5027]

Dependency Upgrades / CVE fixes:

Several CVEs were fixed:

CVE Fixes:

Dependency Upgrades / CVE fixes

Fixed multiple CVEs: CVE-2026-33186 (gRPC 1.79.3), CVE-2026-27143 (Go 1.26.4), and 8 in x/crypto 0.52.0 (CVE-2026-42508, CVE-2026-39831, CVE-2026-46595, CVE-2026-39830, CVE-2026-39832, CVE-2026-39834, CVE-2026-39833, CVE-2025-22869).

Upgraded golang.org/x/crypto to v0.52.0 and golang to 1.26.5 to fix CVEs

New Features

• Kernel Reader Support for Regional Buckets: Extended Kernel Reader capabilities to Regional buckets to significantly improve read throughput. (Note: Kernel reader is the default read mode in Rapid buckets since 3.7.1 with no minimum kernel version requirements or changes to existing request sizes).

  • How It Works: The Kernel Reader path relies directly on the Linux kernel's readahead mechanism for prefetching and enables asynchronous reads. We have optimized the default kernel parameters to streamline the read pipeline and maximize throughput.

  • Prerequisites: To use this read path on regional buckets, GCSFuse configures a few kernel parameters. These configuration changes are fully managed in the GKE environment. On non-GKE environments, GCSFuse requires sudo permissions or users must manually configure fuse max pages limit before mount and read_ahead_kb, max_background, and congestion_threshold after mount. Default config values:

    • Fuse max pages limit: no. of pages needed for 16MB on the machine (4096 on a machine with 4K page size)
    • read_ahead_kb: 131072
    • max_background: min(max(12, 2*numCPU),96)
    • congestion_threshold: (3 * max_background)/4

    Manual configuration of these settings is shown below using a c4-standard-192 instance:

    ## Before mount
    echo 4096 | sudo tee /proc/sys/fs/fuse/max_pages_limit
    
    ## After mount
    export MOUNT_POINT=<mount path>
    
    echo 131072 | sudo tee /sys/class/bdi/0:$(stat -c "%d" $MOUNT_POINT)/read_ahead_kb
    echo 96 | sudo tee /sys/fs/fuse/connections/$(stat -c "%d" $MOUNT_POINT)/max_background
    echo 72 | sudo tee /sys/fs/fuse/connections/$(stat -c "%d" $MOUNT_POINT)/congestion_threshold

  • Opt-in & Kernel Requirements: You can opt in for kernel reader mode in Regional buckets using the --enable-kernel-reader command-line flag (or setting file-system.enable-kernel-reader: true in your configuration file). Using this feature requires Linux kernel 6.13+ or the latest Container-Optimized OS (COS) image (supported on COS with kernel 6.12 as well via cherry-picked patch).

  • Performance: On regional buckets, we see sequential read performance from a single user thread reaching up to 2.5 GB/s (~8x improvement over current read path). We also see performance improvement for large random reads (~3x for 16MB random reads).

  • Larger Request Processing: Support for larger FUSE request sizes is available when this feature is enabled(applicable only for regional buckets). Read requests up to 16MB are supported by default, while write requests are limited to 1MB.

  • Memory Usage Note (Regional Only): Enabling kernel reader on regional buckets increases the FUSE max pages limit and activates asynchronous reads. While this significantly accelerates large read operations, it may result in slightly higher overall memory consumption (up to 15MB per read request).

• Negative Stat Cache Enhancements: The existing negative stat cache has been updated to also store implicit directories. This optimizes the polling of missing directories when frequently checking for non-existent objects [PR#4729].

Bug fixes & Improvements

• LookupInode Latency: Optimized LookupInode latency for Hierarchical Namespace (HNS) buckets by executing GetFolder and StatObject calls concurrently as a race, cutting down the overall time to resolve inodes [PR#4772].
• Heap Allocation Optimization: Optimized the fetchCoreEntity internal function to avoid unnecessary heap allocations, improving memory efficiency during filesystem operations [PR#4790].
• Error Unwrapping for NotFoundError: Implemented error unwrapping for NotFoundError by adding an Unwrap() error method. This ensures that calling RmDir (or os.Remove) on an explicit directory deleted out-of-band directly in GCS correctly maps to a POSIX ENOENT (os.ErrNotExist) response instead of a generic syscall.EIO input/output error [PR#4709].
• Tracing Attributes: Enhanced telemetry by adding read.offset and read.size attributes to fs.file.read traces, providing more granular tracing support for file read operations [PR#4822].
• BufferedReader Leak Fix: Fixed a resource leak in BufferedReader by ensuring that inflight prefetch blocks are eagerly released on non-EOF read errors. Previously, repeated transient read errors would leak blocks, shrink the global block budget mount-wide, grow RSS memory, and cause the Destroy() method to block for its 10-second timeout [PR#4840].
• Log Severity Adjustment: Changed the log severity for the fallback action in streaming writes from INFO down to TRACE, which reduces noise in standard logs [PR#4854].
• Metrics Double Counting Fix: Fixed a double counting issue for the read bytes count metrics in both the Kernel Range Reader and Buffered Reader. This occurred because the underlying monitoringReadCloser (which wraps the GCS reader) already increments the read bytes count internally [PR#4879].

Dependency Upgrades / CVE fixes

• Bumped the go-dependencies group with 5 updates in the root directory, including OpenTelemetry (exporter/metric, exporter/trace) and golang.org/x packages (sync, sys, text) to ensure better stability and security [PR#4771].