kernel/fs: Notify node monitor when opening files with O_TRUNC

Opening files with the O_TRUNC flag will now notify the node monitor if
this resulted in the file size changing.
Implemented on filesystems with write support:
 * BFS
 * EXT2
 * FAT
 * NTFS
 * write_overlay

Change-Id: I4ae7d6b93727a9cc83f64d649b118beb94b16657
Reviewed-on: https://review.haiku-os.org/c/haiku/+/10923
Reviewed-by: waddlesplash <[email protected]>
Haiku-Format: Haiku-format Bot <[email protected]>
Tested-by: Commit checker robot <[email protected]>

src/add-ons/kernel/file_systems/bfs/kernel_interface.cpp

@@ -1384,6 +1384,11 @@ bfs_open(fs_volume* _volume, fs_vnode* _node, int openMode, void** _cookie)
 			status = transaction.Done();
 		if (status != B_OK)
 			return status;
+
+		if (cookie->last_size != 0) {
+			cookie->last_size = inode->Size();
+			notify_stat_changed(volume->ID(), inode->ParentID(), inode->ID(), B_STAT_SIZE);
+		}
 	}
 
 	fileCacheEnabler.Detach();

src/add-ons/kernel/file_systems/ext2/kernel_interface.cpp

@@ -1164,7 +1164,10 @@ ext2_open(fs_volume* _volume, fs_vnode* _node, int openMode, void** _cookie)
 		if (status != B_OK)
 			return status;
 
-		// TODO: No need to notify file size changed?
+		if (cookie->last_size != 0) {
+			cookie->last_size = inode->Size();
+			notify_stat_changed(volume->ID(), -1, inode->ID(), B_STAT_SIZE);
+		}
 	}
 
 	fileCacheEnabler.Detach();

src/add-ons/kernel/file_systems/fat/kernel_interface.cpp

@@ -2207,6 +2207,11 @@ dosfs_open(fs_volume* volume, fs_vnode* vnode, int openMode, void** _cookie)
 		status = file_cache_set_size(bsdNode->v_cache, 0);
 		if (status != B_OK)
 			RETURN_ERROR(status);
+
+		if (cookie->fLastSize != 0) {
+			cookie->fLastSize = fatNode->de_FileSize;
+			notify_stat_changed(volume->id, bsdNode->v_parent, fatNode->de_inode, B_STAT_SIZE);
+		}
 	}
 
 	cookieDeleter.Detach();

src/add-ons/kernel/file_systems/layers/write_overlay/write_overlay.cpp

@@ -582,9 +582,11 @@ OverlayInode::Open(int openMode, void **_cookie)
 	*_cookie = cookie;
 
 	if (fIsVirtual) {
-		if (openMode & O_TRUNC) {
+		if ((openMode & O_TRUNC) && fStat.st_size != 0) {
 			fStat.st_size = 0;
 			_TrimBuffers();
+
+			notify_stat_changed(SuperVolume()->id, -1, fInodeNumber, B_STAT_SIZE);
 		}
 
 		return B_OK;
@@ -600,6 +602,8 @@ OverlayInode::Open(int openMode, void **_cookie)
 			_TrimBuffers();
 			if (!fIsDataModified)
 				SetDataModified();
+
+			notify_stat_changed(SuperVolume()->id, -1, fInodeNumber, B_STAT_SIZE);
 		}
 	}
 

src/add-ons/kernel/file_systems/ntfs/kernel_interface.cpp

@@ -831,6 +831,8 @@ fs_open(fs_volume* _volume, fs_vnode* _node, int openMode, void** _cookie)
 	ObjectDeleter<file_cookie> cookieDeleter(cookie);
 
 	cookie->open_mode = openMode;
+	cookie->last_size = node->size;
+	cookie->last_notification = system_time();
 
 	// We don't actually support uncached mode; it would require us to handle
 	// passing user buffers to libntfs, among other things.
@@ -858,6 +860,11 @@ fs_open(fs_volume* _volume, fs_vnode* _node, int openMode, void** _cookie)
 			return errno;
 		node->size = na->data_size;
 		file_cache_set_size(node->file_cache, node->size);
+
+		if (cookie->last_size != 0) {
+			cookie->last_size = node->size;
+			notify_stat_changed(_volume->id, node->parent_inode, node->inode, B_STAT_SIZE);
+		}
 	}
 
 	cookieDeleter.Detach();