While looking at the problem that Li Lingfeng reported [1] around callback queueing failures, I noticed that there were potential scenarios where the callback workqueue jobs could run concurrently with an rpc_task. Since they touch some of the same fields, this is incorrect at best and potentially dangerous. This patchset adds a new mechanism for ensuring that the same nfsd4_callback can't run concurrently with itself, regardless of where it is in its execution. This also gives us a more sure mechanism for handling the places where we need to take and hold a reference on an object while the callback is running. This should also fix the problem that Li Lingfeng reported, since queueing the work from nfsd4_cb_release() should never fail. Note that their earlier patch (fdf5c9413ea) should be dropped from nfsd-testing before this will apply cleanly. [1]: https://lore.kernel.org/linux-nfs/20250218135423.1487309-1-lilingfeng3@xxxxxxxxxx/ Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> --- Changes in v2: - added patche to handle rpc_call_async() errors - rename NFSD4_CALLBACK_RESTART to NFSD4_CALLBACK_REQUEUE - add patch to replace CB_GETATTR_BUSY with NFSD4_CALLBACK_REQUEUE - Link to v1: https://lore.kernel.org/r/20250218-nfsd-callback-v1-0-14f966967dd8@xxxxxxxxxx --- Jeff Layton (5): nfsd: prevent callback tasks running concurrently nfsd: eliminate cl_ra_cblist and NFSD4_CLIENT_CB_RECALL_ANY nfsd: replace CB_GETATTR_BUSY with NFSD4_CALLBACK_RUNNING nfsd: move cb_need_restart flag into cb_flags nfsd: handle errors from rpc_call_async() fs/nfsd/nfs4callback.c | 26 +++++++++++++++++--------- fs/nfsd/nfs4layouts.c | 7 ++++--- fs/nfsd/nfs4proc.c | 2 +- fs/nfsd/nfs4state.c | 31 ++++++++++++++----------------- fs/nfsd/state.h | 18 +++++++++++------- fs/nfsd/trace.h | 2 +- 6 files changed, 48 insertions(+), 38 deletions(-) --- base-commit: b7e85fd7c8964e31f8fa1cf7333b12f442b642f1 change-id: 20250218-nfsd-callback-f723b8498c78 Best regards, -- Jeff Layton <jlayton@xxxxxxxxxx>
