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01ae1faa96
Implement fsmonitor for Linux using the inotify API, bringing it to feature parity with existing Windows and macOS implementations. The Linux implementation uses inotify to monitor filesystem events. Unlike macOS's FSEvents which can watch a single root directory, inotify requires registering watches on every directory of interest. The implementation carefully handles directory renames and moves using inotify's cookie mechanism to track IN_MOVED_FROM/IN_MOVED_TO event pairs. Key implementation details: - Uses inotify_init1(O_NONBLOCK) for non-blocking event monitoring - Maintains bidirectional hashmaps between watch descriptors and paths for efficient event processing - Handles directory creation, deletion, and renames dynamically - Detects remote filesystems (NFS, CIFS, SMB, etc.) via statfs() - Falls back to $HOME/.git-fsmonitor-* for socket when .git is remote - Creates batches lazily (only for actual file events, not cookies) to avoid spurious sequence number increments Build configuration: - Enabled via FSMONITOR_DAEMON_BACKEND=linux and FSMONITOR_OS_SETTINGS=linux - Requires NO_PTHREADS and NO_UNIX_SOCKETS to be unset - Adds HAVE_LINUX_MAGIC_H for filesystem type detection Documentation updated to note that fsmonitor.socketDir is now supported on both Mac OS and Linux, and adds a section about inotify watch limits. Testing performed: - Build succeeds with standard flags and SANITIZE=address - All t7527-builtin-fsmonitor.sh tests pass on local filesystems - Remote filesystem detection correctly rejects network mounts Issues addressed from PR #1352 (git/git) review comments: - GPLv3 ME_REMOTE macro: Rewrote remote filesystem detection from scratch using statfs() and linux/magic.h constants (no GPLv3 code) - Memory leak on inotify_init1 failure: Added FREE_AND_NULL cleanup - Unsafe hashmap iteration in dtor: Collect entries first, then modify - Missing null checks in stop_async: Added proper guard conditions - dirname() modifying argument: Create copy with xstrdup() first - Non-portable f_fsid.__val: Use memcmp() for fsid comparison - Missing worktree null check: Added BUG() for null worktree - Header updates: Use git-compat-util.h, hash_to_hex_algop() - Code style: Use xstrdup() not xmemdupz(), proper pointer style Issues addressed from PR #1667 (git/git) review comments: - EINTR handling: read() now handles both EAGAIN and EINTR - Trailing pipe in log_mask_set: Added strbuf_strip_suffix() - Unchecked add_watch return: Now logs failure in rename_dir() - String building: Consolidated strbuf operations with strbuf_addf() - Translation markers: Added _() to all error_errno() messages Based on work from https://github.com/git/git/pull/1352 by Eric DeCosta, and https://github.com/git/git/pull/1667 by Marziyeh Esipreh, updated to work with the current codebase and address all review feedback. Signed-off-by: Paul Tarjan <github@paulisageek.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
127 lines
4.1 KiB
Plaintext
127 lines
4.1 KiB
Plaintext
git-fsmonitor{litdd}daemon(1)
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=============================
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NAME
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----
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git-fsmonitor--daemon - A Built-in Filesystem Monitor
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SYNOPSIS
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--------
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[verse]
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'git fsmonitor{litdd}daemon' start
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'git fsmonitor{litdd}daemon' run
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'git fsmonitor{litdd}daemon' stop
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'git fsmonitor{litdd}daemon' status
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DESCRIPTION
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-----------
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A daemon to watch the working directory for file and directory
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changes using platform-specific filesystem notification facilities.
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This daemon communicates directly with commands like `git status`
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using the link:technical/api-simple-ipc.html[simple IPC] interface
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instead of the slower linkgit:githooks[5] interface.
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This daemon is built into Git so that no third-party tools are
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required.
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OPTIONS
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-------
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start::
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Starts a daemon in the background.
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run::
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Runs a daemon in the foreground.
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stop::
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Stops the daemon running in the current working
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directory, if present.
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status::
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Exits with zero status if a daemon is watching the
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current working directory.
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REMARKS
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-------
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This daemon is a long running process used to watch a single working
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directory and maintain a list of the recently changed files and
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directories. Performance of commands such as `git status` can be
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increased if they just ask for a summary of changes to the working
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directory and can avoid scanning the disk.
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When `core.fsmonitor` is set to `true` (see linkgit:git-config[1])
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commands, such as `git status`, will ask the daemon for changes and
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automatically start it (if necessary).
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For more information see the "File System Monitor" section in
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linkgit:git-update-index[1].
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CAVEATS
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-------
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The fsmonitor daemon does not currently know about submodules and does
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not know to filter out filesystem events that happen within a
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submodule. If fsmonitor daemon is watching a super repo and a file is
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modified within the working directory of a submodule, it will report
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the change (as happening against the super repo). However, the client
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will properly ignore these extra events, so performance may be affected
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but it will not cause an incorrect result.
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By default, the fsmonitor daemon refuses to work with network-mounted
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repositories; this may be overridden by setting `fsmonitor.allowRemote` to
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`true`. Note, however, that the fsmonitor daemon is not guaranteed to work
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correctly with all network-mounted repositories, so such use is considered
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experimental.
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On Mac OS and Linux, the inter-process communication (IPC) between various Git
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commands and the fsmonitor daemon is done via a Unix domain socket (UDS) -- a
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special type of file -- which is supported by native Mac OS and Linux filesystems,
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but not on network-mounted filesystems, NTFS, or FAT32. Other filesystems
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may or may not have the needed support; the fsmonitor daemon is not guaranteed
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to work with these filesystems and such use is considered experimental.
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By default, the socket is created in the `.git` directory. However, if the
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`.git` directory is on a network-mounted filesystem, it will instead be
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created at `$HOME/.git-fsmonitor-*` unless `$HOME` itself is on a
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network-mounted filesystem, in which case you must set the configuration
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variable `fsmonitor.socketDir` to the path of a directory on a native
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filesystem in which to create the socket file.
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If none of the above directories (`.git`, `$HOME`, or `fsmonitor.socketDir`)
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is on a native filesystem the fsmonitor daemon will report an
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error that will cause the daemon and the currently running command to exit.
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LINUX CAVEATS
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~~~~~~~~~~~~~
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On Linux, the fsmonitor daemon uses inotify to monitor filesystem events.
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The inotify system has per-user limits on the number of watches that can
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be created. The default limit is typically 8192 watches per user.
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For large repositories with many directories, you may need to increase
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this limit. Check the current limit with:
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cat /proc/sys/fs/inotify/max_user_watches
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To temporarily increase the limit:
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sudo sysctl fs.inotify.max_user_watches=65536
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To make the change permanent, add to `/etc/sysctl.conf`:
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fs.inotify.max_user_watches=65536
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CONFIGURATION
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-------------
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include::includes/cmd-config-section-all.adoc[]
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include::config/fsmonitor--daemon.adoc[]
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GIT
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---
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Part of the linkgit:git[1] suite
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