feat(fs): implement inotify filesystem event notification - #2164
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Implements inotify (issue DragonOS-Community#2151): the fsnotify core notification layer, the inotify pseudo-device, 4 syscalls (init/init1/add_watch/rm_watch), and VFS write-path hooks for all standard events (create/delete/move/ modify/access/close/attrib/self events). Architecture: - fsnotify/ unified dispatch layer: global inode_id -> Weak<mark> index, TOTAL_WATCHES atomic fast-path (zero cost when no watches), lock-family separation (global index lock / events lock / wd lock never nested). - inotify.rs device: InotifyInode implements IndexNode + PollableInode, epoll-integrated via LockedEPItemLinkedList, exact inotify_event layout (name field aligned to sizeof(inotify_event)=16, matching Linux ABI). - VFS hooks placed in syscall-core layer (vcore/open/rename_utils/...), NOT per-filesystem: single anchor covers ext4/tmpfs/overlayfs/fuse. Hooks fire only after success and never alter syscall return values. Review fixes incorporated: - Directory watches receive child content events (issue B): IN_MODIFY/ ACCESS/OPEN/CLOSE delivered to parent dir watch with child name. - Guard DELETE_SELF on hardlink unlink/rename-over: only emit when i_nlink reaches 0, matching Linux fsnotify_link_count() semantics. - Fix MountFSInode downcast: MountFSInode::as_any_ref() returns the inner inode's Any, so downcast_ref::<MountFSInode>() always fails. Use downcast_arc instead so parent resolution works for child content event delivery. - TOTAL_WATCHES counter: avoid double-decrement / double-increment. Test: user/apps/tests/dunitest/suites/normal/inotify_dir_watch.cc covers directory-watch child content events and self-watch MODIFY. Design doc: docs/kernel/filesystem/inotify.md Signed-off-by: sparkzky <sparkhhhhhhhhhh@outlook.com>
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Summary
Implements inotify (issue #2151): filesystem event notification with
inotify_init1/inotify_add_watch/inotify_rm_watch/read, the full standard event set, epoll integration, and exactinotify_eventABI.Design doc:
docs/kernel/filesystem/inotify.md. Behavior targets Linux 6.6.Architecture (3 layers)
fs/notify/-style): globalinode_id -> Weak<mark>index,TOTAL_WATCHESatomic fast-path (zero cost when no watches), lock-family separation (global index lock / events lock / wd lock never nested). Hooks fire only after success and never alter syscall return values.inotify.rs):InotifyInodeimplementsIndexNode + PollableInode, epoll-integrated viaLockedEPItemLinkedList, exactinotify_eventlayout (name field aligned tosizeof(inotify_event)=16, matching the Linux 6.6 ABI).vcore/open/rename_utils/...), not per-filesystem: a single anchor covers ext4/tmpfs/overlayfs/fuse.What this PR adds beyond the initial implementation
The initial implementation was put through a 3-way adversarial review (independent reviewers) + independent verification. This PR includes both the feature and the resulting fixes:
Directory watches now receive child content events (the primary inotify use case, e.g.
inotifywait -m /dir). Previously only namespace events (create/delete/move) reached directory watches;IN_MODIFY/ACCESS/OPEN/CLOSEon children were silently dropped. Resolved by snapshotting the parent dir + child name once atFileconstruction (gated byhas_any_watchfor zero cost when unused) and routing content events to both the parent (with name) and self watch. This also makesIN_EXCL_UNLINKeffective.Other review fixes (all verified):
TOTAL_WATCHESdouble-count onadd_watch(broke the no-watch fast path).add_watchTOCTOU: concurrent same-inode adds created duplicate marks.IN_EXCL_UNLINKpolarity was inverted.fallocate: restored theoffset+lenoverflow guard removed during theIN_MODIFYrefactor.renameoverwriting an existing target now emitsIN_DELETE/IN_DELETE_SELF(was a ghost-watch leak).RENAME_EXCHANGEnow emits the full 4 namespace events + 2MOVE_SELFwith two cookies.Testing
normal/inotify_dir_watch(directory-watch child content events + self-watch sanity), added to the whitelist so CI runs it.make kernel).docs/impl-notes/): rename-after-open yields a stale parent snapshot (EXCL_UNLINK covers unlink);IN_ATTRIB-to-parent via fd-based setattr is not yet wired; unmount does not emitIN_UNMOUNT(watch reclaims on fd close).Checklist
make kernelcompiles