Store `fs` in `FsEventPublisher`

kernel/src/fs/notify/inotify.rs

@@ -145,7 +145,7 @@ impl InotifyFile {
                 continue;
             }
 
-            // The subscriber is dead because it's a one-shot subscriber or the inode is dead.
+            // The subscriber is dead because it's a one-shot subscriber.
             // The watch is considered removed.
             let Some(subscriber) = entry.subscriber.upgrade() else {
                 let wd = *wd;
@@ -182,7 +182,6 @@ impl InotifyFile {
                 "adding an inotify watch to a deleted inode is not supported yet"
             );
         }
-        inode.fs().fs_event_subscriber_stats().add_subscriber();
 
         let wd = inotify_subscriber.wd();
         let entry = SubscriberEntry {
@@ -209,13 +208,10 @@ impl InotifyFile {
             _ => return_errno_with_message!(Errno::EINVAL, "the inotify watch does not exist"),
         };
 
-        if inode
+        inode
             .fs_event_publisher()
             .unwrap()
-            .remove_subscriber(&(subscriber as _))
-        {
-            inode.fs().fs_event_subscriber_stats().remove_subscriber();
-        }
+            .remove_subscriber(&(subscriber as _));
 
         Ok(())
     }

kernel/src/fs/notify/mod.rs

@@ -17,7 +17,7 @@ use crate::{
 
 pub mod inotify;
 
-use super::utils::{Inode, InodeExt, InodeType};
+use super::utils::{FileSystem, Inode, InodeExt, InodeType};
 
 /// Publishes filesystem events to subscribers.
 ///
@@ -25,12 +25,14 @@ use super::utils::{Inode, InodeExt, InodeType};
 /// subscribers interested in filesystem events. When an event occurs, the publisher
 /// notifies all subscribers whose interesting events match the event.
 pub struct FsEventPublisher {
-    /// List of FS event subscribers.
+    /// A list of FS event subscribers.
     subscribers: RwLock<Vec<Arc<dyn FsEventSubscriber>>>,
     /// All interesting FS event types (aggregated from all subscribers).
     all_interesting_events: AtomicFsEvents,
     /// Whether this publisher still accepts new subscribers.
     accepts_new_subscribers: AtomicBool,
+    /// A weak reference to the file system.
+    fs: Weak<dyn FileSystem>,
 }
 
 impl Debug for FsEventPublisher {
@@ -41,18 +43,13 @@ impl Debug for FsEventPublisher {
     }
 }
 
-impl Default for FsEventPublisher {
-    fn default() -> Self {
-        Self::new()
-    }
-}
-
 impl FsEventPublisher {
-    pub fn new() -> Self {
+    pub fn new(fs: Weak<dyn FileSystem>) -> Self {
         Self {
             subscribers: RwLock::new(Vec::new()),
             all_interesting_events: AtomicFsEvents::new(FsEvents::empty()),
             accepts_new_subscribers: AtomicBool::new(true),
+            fs,
         }
     }
 
@@ -72,6 +69,10 @@ impl FsEventPublisher {
 
         subscribers.push(subscriber);
 
+        if let Some(fs) = self.fs.upgrade() {
+            fs.fs_event_subscriber_stats().add_subscriber();
+        }
+
         true
     }
 
@@ -87,6 +88,10 @@ impl FsEventPublisher {
             subscriber.deliver_event(FsEvents::IN_IGNORED, None);
         }
 
+        if let Some(fs) = self.fs.upgrade() {
+            fs.fs_event_subscriber_stats().remove_subscriber();
+        }
+
         removed
     }
 
@@ -104,6 +109,11 @@ impl FsEventPublisher {
         self.all_interesting_events
             .store(FsEvents::empty(), Ordering::Relaxed);
 
+        if let Some(fs) = self.fs.upgrade() {
+            fs.fs_event_subscriber_stats()
+                .remove_subscribers(num_subscribers);
+        }
+
         num_subscribers
     }
 

kernel/src/fs/utils/inode_ext.rs

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MPL-2.0
 
-use alloc::boxed::ThinBox;
+use alloc::{boxed::ThinBox, sync::Arc};
 
 use super::{FlockList, Inode, RangeLockList};
 use crate::fs::notify::FsEventPublisher;
@@ -59,7 +59,7 @@ impl InodeExt for dyn Inode {
     fn fs_event_publisher_or_init(&self) -> &FsEventPublisher {
         self.extension()
             .group1()
-            .call_once(|| ThinBox::new_unsize(FsEventPublisher::new()))
+            .call_once(|| ThinBox::new_unsize(FsEventPublisher::new(Arc::downgrade(&self.fs()))))
             .downcast_ref()
             .unwrap()
     }