On Thu, 2024-09-12 at 13:32 +0200, Christian Brauner wrote: > On Thu, Sep 12, 2024 at 07:08:07AM GMT, Jeff Layton wrote: > > On Wed, 2024-09-11 at 15:42 -0400, Benjamin Coddington wrote: > > > Last year both GFS2 and OCFS2 had some work done to make their locking more > > > robust when exported over NFS. Unfortunately, part of that work caused both > > > NLM (for NFS v3 exports) and kNFSD (for NFSv4.1+ exports) to no longer send > > > lock notifications to clients. > > > > > > This in itself is not a huge problem because most NFS clients will still > > > poll the server in order to acquire a conflicted lock, but now that I've > > > noticed it I can't help but try to fix it because there are big advantages > > > for setups that might depend on timely lock notifications, and we've > > > supported that as a feature for a long time. > > > > > > Its important for NLM and kNFSD that they do not block their kernel threads > > > inside filesystem's file_lock implementations because that can produce > > > deadlocks. We used to make sure of this by only trusting that > > > posix_lock_file() can correctly handle blocking lock calls asynchronously, > > > so the lock managers would only setup their file_lock requests for async > > > callbacks if the filesystem did not define its own lock() file operation. > > > > > > However, when GFS2 and OCFS2 grew the capability to correctly > > > handle blocking lock requests asynchronously, they started signalling this > > > behavior with EXPORT_OP_ASYNC_LOCK, and the check for also trusting > > > posix_lock_file() was inadvertently dropped, so now most filesystems no > > > longer produce lock notifications when exported over NFS. > > > > > > I tried to fix this by simply including the old check for lock(), but the > > > resulting include mess and layering violations was more than I could accept. > > > There's a much cleaner way presented here using an fop_flag, which while > > > potentially flag-greedy, greatly simplifies the problem and grooms the > > > way for future uses by both filesystems and lock managers alike. > > > > > > Criticism welcomed, > > > Ben > > > > > > Benjamin Coddington (4): > > > fs: Introduce FOP_ASYNC_LOCK > > > gfs2/ocfs2: set FOP_ASYNC_LOCK > > > NLM/NFSD: Fix lock notifications for async-capable filesystems > > > exportfs: Remove EXPORT_OP_ASYNC_LOCK > > > > > > Documentation/filesystems/nfs/exporting.rst | 7 ------- > > > fs/gfs2/export.c | 1 - > > > fs/gfs2/file.c | 2 ++ > > > fs/lockd/svclock.c | 5 ++--- > > > fs/nfsd/nfs4state.c | 19 ++++--------------- > > > fs/ocfs2/export.c | 1 - > > > fs/ocfs2/file.c | 2 ++ > > > include/linux/exportfs.h | 13 ------------- > > > include/linux/filelock.h | 5 +++++ > > > include/linux/fs.h | 2 ++ > > > 10 files changed, 17 insertions(+), 40 deletions(-) > > > > > > > Thanks for fixing this up, Ben! > > > > Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx> > > It might be a bit late for v6.12 so I would stuff this into a branch for > v6.13. Sound ok? Ok. I figured Chuck would take this set, but I guess it is more VFS-y. I think this is reasonably safe though, so if Ben needs it before then, we could pull it in sooner. -- Jeff Layton <jlayton@xxxxxxxxxx>
