Linux 6.17: fuse: bound the attribute timeout of an inode a DLM lock was taken on

fs/fuse/file.c

@@ -3497,6 +3497,8 @@ static int fuse_get_page_mkwrite_lock(struct file *file, loff_t offset, size_t l
 		fuse_abort_conn(fc);
 		err = -EINVAL;
 	}
+	if (!err && fc->dlm)
+		fuse_dlm_attr_timeout(get_fuse_inode(inode));
 	return err;
 }
 

fs/fuse/fuse_dlm_cache.c

@@ -827,6 +827,8 @@ int fuse_get_dlm_lock(struct file *file, loff_t offset,
 	if (err)
 		return err;
 
+	fuse_dlm_attr_timeout(fi);
+
 	if (inarg.start < outarg.start || inarg.end > outarg.end) {
 		/* fuse server is seriously broken */
 		pr_warn("fuse: dlm lock request for %llu:%llu returned %llu:%llu bytes\n",

fs/fuse/fuse_i.h

@@ -338,6 +338,12 @@ enum {
 	 * See fuse_reverse_inval_inode()/fuse_file_io_open().
 	 */
 	FUSE_I_FORCE_DIO,
+	/*
+	 * A DLM lock was taken on this inode and no attribute reply has
+	 * arrived since: i_time is bounded to dlm_attr_timeout seconds from
+	 * the lock, see fuse_dlm_attr_timeout().
+	 */
+	FUSE_I_DLM_LOCKED,
 };
 
 struct fuse_conn;
@@ -1633,6 +1639,9 @@ struct inode *fuse_ilookup(struct fuse_conn *fc, u64 nodeid,
 int fuse_reverse_inval_inode(struct fuse_conn *fc, u64 nodeid,
 			     loff_t offset, loff_t len);
 
+/* A DLM lock was taken on @fi: bound its attribute timeout until the next reply */
+void fuse_dlm_attr_timeout(struct fuse_inode *fi);
+
 /**
  * File-system tells the kernel to invalidate parent attributes and
  * the dentry matching parent/name.

fs/fuse/inode.c

@@ -55,6 +55,39 @@ module_param(enable_notify_dio, bool, 0644);
 MODULE_PARM_DESC(enable_notify_dio,
 		 "Latch a contended inode to direct IO on an invalidation notify storm");
 
+/*
+ * Attribute timeout of an inode once a DLM lock was taken on it, in
+ * seconds: i_time is bounded to it until the next attribute reply from
+ * the server, so a GETATTR goes out at most this long after the lock.
+ * 0 leaves the server's timeout alone.
+ */
+static unsigned int __read_mostly dlm_attr_timeout = 30;
+module_param(dlm_attr_timeout, uint, 0644);
+MODULE_PARM_DESC(dlm_attr_timeout,
+		 "Seconds until the attributes of an inode a DLM lock was taken on are fetched again (0 = server's timeout)");
+
+void fuse_dlm_attr_timeout(struct fuse_inode *fi)
+{
+	struct fuse_conn *fc = get_fuse_conn(&fi->inode);
+	unsigned int timeout = READ_ONCE(dlm_attr_timeout);
+	u64 valid;
+
+	if (!timeout)
+		return;
+	valid = get_jiffies_64() + secs_to_jiffies(timeout);
+
+	spin_lock(&fi->lock);
+	/*
+	 * Only a reply to a request sent after the lock may end the bound:
+	 * one to an earlier request is discarded by fuse_change_attributes_i().
+	 */
+	if (!test_and_set_bit(FUSE_I_DLM_LOCKED, &fi->state))
+		fi->attr_version = atomic64_inc_return(&fc->attr_version);
+	if (time_after64(fi->i_time, valid))
+		fi->i_time = valid;
+	spin_unlock(&fi->lock);
+}
+
 static struct kmem_cache *fuse_inode_cachep;
 struct list_head fuse_conn_list;
 DEFINE_MUTEX(fuse_mutex);
@@ -402,6 +435,9 @@ void fuse_change_attributes_common(struct inode *inode, struct fuse_attr *attr,
 
 	lockdep_assert_held(&fi->lock);
 
+	/* The first attribute reply after a DLM lock ends the bounded timeout */
+	clear_bit(FUSE_I_DLM_LOCKED, &fi->state);
+
 	if (sx) {
 		return fuse_change_attributes_common_sx(inode, attr, sx,
 							attr_valid, cache_mask,