Purge root caches after subvolume deletion

- Clear subprocess roots cache on SIGUSR1 signal to force re-resolution
  of roots after deletion
- Add generation checks to skip processing stale NewRootMessage and
  inode result messages in the main process
- Track deleted subvolume IDs during the deletion process
- Remove deleted subvolumes from globalRoots after deletion completes

This ensures deleted subvolumes are properly purged from all caches and
prevents stale root information from being processed after deletion.

Author: CyberShadow

source/btdu/sample.d

@@ -324,12 +324,15 @@ struct Root
 Root[u64] roots;
 uint generation;
 
-/// Set up SIGUSR1 handler to increment generation counter.
-/// This causes in-flight samples to be discarded by the main process.
+/// Set up SIGUSR1 handler to invalidate root cache and increment generation.
+/// This causes the subprocess to re-resolve roots and the main process to
+/// discard in-flight samples.
 void setupCacheInvalidationHandler()
 {
 	sigaction_t sa;
 	sa.sa_handler = (int) {
+		// Clear the roots cache - will be repopulated on next access
+		roots = null;
 		generation++;
 	};
 	sigemptyset(&sa.sa_mask);

source/btdu/subproc.d

@@ -162,6 +162,10 @@ struct Subprocess
 
 	void handleMessage(NewRootMessage m)
 	{
+		// Discard root info from before the last deletion
+		if (m.generation < currentGeneration)
+			return;
+
 		if (m.rootID in globalRoots)
 			return;
 
@@ -257,6 +261,10 @@ struct Subprocess
 
 	void handleMessage(ResultInodeStartMessage m)
 	{
+		// Skip processing if this sample will be discarded anyway
+		if (result.generation < currentGeneration)
+			return;
+
 		result.haveInode = true;
 		result.havePath = false;
 		result.inodeRoot = (m.rootID in globalRoots).enforce("Unknown inode root");
@@ -267,25 +275,33 @@ struct Subprocess
 
 	void handleMessage(ResultInodeErrorMessage m)
 	{
+		if (result.generation < currentGeneration)
+			return;
 		allPaths ~= GlobalPath(result.inodeRoot.path, subPathRoot.appendError(m.error));
 		result.category = DiskMap.SectorCategory.error;
 	}
 
 	void handleMessage(ResultMessage m)
 	{
+		if (result.generation < currentGeneration)
+			return;
 		result.havePath = true;
 		allPaths ~= GlobalPath(result.inodeRoot.path, subPathRoot.appendPath(m.path));
 	}
 
 	void handleMessage(ResultInodeEndMessage m)
 	{
+		if (result.generation < currentGeneration)
+			return;
 		cast(void) m; // empty message
 		if (!result.havePath)
 			allPaths ~= GlobalPath(result.inodeRoot.path, subPathRoot.appendPath("\0NO_PATH"));
 	}
 
 	void handleMessage(ResultErrorMessage m)
 	{
+		if (result.generation < currentGeneration)
+			return;
 		import core.stdc.errno : ENOENT;
 		allPaths ~= GlobalPath(null, subPathRoot.appendError(m.error));
 		result.haveInode = true;

source/btdu/ui/browser.d

@@ -402,6 +402,9 @@ struct Browser
 					showMessage(format!"Deleted %s."(deleter.items[0].browserPath.humanName));
 				else
 					showMessage(format!"Deleted %d item%s."(deleter.items.length, deleter.items.length > 1 ? "s" : ""));
+				// Purge deleted subvolumes from the root cache
+				foreach (subvolumeID; deleter.deletedSubvolumeIDs)
+					globalRoots.remove(subvolumeID);
 				foreach (item; deleter.items)
 					item.browserPath.remove(item.obeyMarks);
 				invalidateMark();

source/btdu/ui/deletion.d

@@ -33,6 +33,7 @@ import core.thread : Thread;
 import ae.sys.file : listDir, getMounts;
 
 import btrfs : getSubvolumeID, deleteSubvolume;
+import btrfs.c.kerncompat : u64;
 
 import btdu.paths : BrowserPath, Mark;
 import btdu.state : toFilesystemPath;
@@ -85,6 +86,9 @@ struct Deleter
 	}
 	Item[] items;
 
+	/// Subvolume IDs that were deleted (collected during deletion for cache purging)
+	u64[] deletedSubvolumeIDs;
+
 	void prepare(Item[] items)
 	{
 		assert(this.state.status == Status.none);
@@ -105,6 +109,7 @@ struct Deleter
 		assert(this.state.status == Status.ready);
 		this.state.stopping = false;
 		this.state.status = Status.progress;
+		this.deletedSubvolumeIDs = null;
 		this.subvolumeResume.initialize(false, false);
 		this.thread = new Thread(&threadFunc);
 		this.thread.start();
@@ -181,6 +186,10 @@ struct Deleter
 							auto subvolumeID = getSubvolumeID(fd);
 							deleteSubvolume(fd, subvolumeID);
 
+							// Track deleted subvolume for cache purging
+							synchronized (this.thread)
+								this.deletedSubvolumeIDs ~= subvolumeID;
+
 							this.state.status = Status.progress;
 							return; // The ioctl will also unlink the directory entry
 						}