[wangrong1069]

feat(fsmonitor): use recvmmsg for batch event receiving

Replace single-packet recv() with recvmmsg() to drain up to 64
fs_event messages per syscall, reducing system call overhead during
high-event bursts and lowering the risk of dispatcher buffer overflow.

The iovec and mmsghdr arrays are pre-allocated as member variables
and initialized in the VfsSocketReader constructor. Before each
recvmmsg batch call, the iovec pointers are reset because the kernel
may advance them while consuming messages.

The socket is already non-blocking (SOCK_NONBLOCK set by the
dispatcher's socketpair), so flag 0 is used instead of MSG_DONTWAIT.

Event handling logic (path resolution, mount refresh deferral,
pending batch coalescing) is unchanged.

Summary by Sourcery

Enhancements:

• Batch filesystem monitor event reception to process up to 64 messages per system call, reducing overhead and improving resilience during event bursts.

[sourcery-ai]

Reviewer's Guide

Replaces single-message recv() draining with nonblocking recvmmsg() batches of up to 64 fs_event messages, reducing syscall overhead during bursts while retaining the existing event-processing semantics.

Sequence diagram for batched filesystem event receiving

sequenceDiagram
    participant Dispatcher
    participant Reader as VfsSocketReader
    participant Kernel
    participant Watcher

    Dispatcher->>Kernel: send fs_event messages
    Kernel-->>Dispatcher: socketpair delivery
    Reader->>Kernel: recvmmsg(socketFd, msgHeaders, 64, 0, nullptr)
    Kernel-->>Reader: up to 64 fs_event messages
    loop each received message
        Reader->>Reader: resolveAndFilterFullPath(deviceId, event.path)
        Reader->>Reader: append pendingBatch
    end
    Reader->>Watcher: flushPendingBatch()
    Reader->>Kernel: recvmmsg(...)
    Kernel-->>Reader: EAGAIN

Loading

File-Level Changes

Change	Details	Files
Batch socket reads to process multiple filesystem events per system call.	Adds preallocated receive buffers, iovec entries, and message headers for 64 messages. Resets iovec state before each recvmmsg call and uses the existing nonblocking socket with flags set to zero. Iterates over each received message while preserving existing validation, path resolution, mount deferral, and event coalescing behavior.	src/index/fsmonitor/vfsmonitorwatcher.cpp

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[wangrong1069]

/merge

[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: lzwind, wangrong1069

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• debian/deepin/OWNERS

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