@@ -180,6 +180,11 @@ static inline void locks_wake_up(struct file_lock *fl)
wake_up(&fl->c.flc_wait);
}
+static inline bool locks_can_async_lock(const struct file_operations *fops)
+{
+ return !fops->lock || fops->fop_flags & FOP_ASYNC_LOCK;
+}
+
/* fs/locks.c */
void locks_free_lock_context(struct inode *inode);
void locks_free_lock(struct file_lock *fl);
@@ -2074,6 +2074,8 @@ struct file_operations {
#define FOP_DIO_PARALLEL_WRITE ((__force fop_flags_t)(1 << 3))
/* Contains huge pages */
#define FOP_HUGE_PAGES ((__force fop_flags_t)(1 << 4))
+/* Supports asynchronous lock callbacks */
+#define FOP_ASYNC_LOCK ((__force fop_flags_t)(1 << 5))
/* Wrap a directory iterator that needs exclusive inode access */
int wrap_directory_iterator(struct file *, struct dir_context *,
Some lock managers (NLM, kNFSD) fastidiously avoid blocking their kernel threads while servicing blocking locks. If a filesystem supports asynchronous lock requests those lock managers can use notifications to quickly inform clients they have acquired a file lock. Historically, only posix_lock_file() was capable of supporting asynchronous locks so the check for support was simply file_operations->lock(), but with recent changes in DLM, both GFS2 and OCFS2 also support asynchronous locks and have started signalling their support with EXPORT_OP_ASYNC_LOCK. We recently noticed that those changes dropped the checks for whether a filesystem simply defaults to posix_lock_file(), so async lock notifications have not been attempted for NLM and NFSv4.1+ for most filesystems. While trying to fix this it has become clear that testing both the export flag combined with testing ->lock() creates quite a layering mess. It seems appropriate to signal support with a fop_flag. Add FOP_ASYNC_LOCK so that filesystems with ->lock() can signal their capability to handle lock requests asynchronously. Add a helper for lock managers to properly test that support. Signed-off-by: Benjamin Coddington <bcodding@redhat.com> --- include/linux/filelock.h | 5 +++++ include/linux/fs.h | 2 ++ 2 files changed, 7 insertions(+)