This series of patches implement the NFSv4 Courteous Server. A server which does not immediately expunge the state on lease expiration is known as a Courteous Server. A Courteous Server continues to recognize previously generated state tokens as valid until conflict arises between the expired state and the requests from another client, or the server reboots. v2 patch includes: . add new callback, lm_expire_lock, to lock_manager_operations to allow the lock manager to take appropriate action with conflict lock. . handle conflicts of NFSv4 locks with NFSv3/NLM and local locks. . expire courtesy client after 24hr if client has not reconnected. . do not allow expired client to become courtesy client if there are waiters for client's locks. . modify client_info_show to show courtesy client and seconds from last renew. . fix a problem with NFSv4.1 server where the it keeps returning SEQ4_STATUS_CB_PATH_DOWN in the successful SEQUENCE reply, after the courtesy client reconnects, causing the client to keep sending BCTS requests to server. v3 patch includes: . modified posix_test_lock to check and resolve conflict locks to handle NLM TEST and NFSv4 LOCKT requests. . separate out fix for back channel stuck in SEQ4_STATUS_CB_PATH_DOWN. v4 patch includes: . rework nfsd_check_courtesy to avoid dead lock of fl_lock and client_lock by asking the laudromat thread to destroy the courtesy client. . handle NFSv4 share reservation conflicts with courtesy client. This includes conflicts between access mode and deny mode and vice versa. . drop the patch for back channel stuck in SEQ4_STATUS_CB_PATH_DOWN. v5 patch includes: . fix recursive locking of file_rwsem from posix_lock_file. . retest with LOCKDEP enabled. v6 patch includes: . merge witn 5.15-rc7 . fix a bug in nfs4_check_deny_bmap that did not check for matched nfs4_file before checking for access/deny conflict. This bug causes pynfs OPEN18 to fail since the server taking too long to release lots of un-conflict clients' state. . enhance share reservation conflict handler to handle case where a large number of conflict courtesy clients need to be expired. The 1st 100 clients are expired synchronously and the rest are expired in the background by the laundromat and NFS4ERR_DELAY is returned to the NFS client. This is needed to prevent the NFS client from timing out waiting got the reply. v7 patch includes: . Fix race condition in posix_test_lock and posix_lock_inode after dropping spinlock. . Enhance nfsd4_fl_expire_lock to work with with new lm_expire_lock callback . Always resolve share reservation conflicts asynchrously. . Fix bug in nfs4_laundromat where spinlock is not used when scanning cl_ownerstr_hashtbl. . Fix bug in nfs4_laundromat where idr_get_next was called with incorrect 'id'. . Merge nfs4_destroy_courtesy_client into nfsd4_fl_expire_lock. v8 patch includes: . Fix warning in nfsd4_fl_expire_lock reported by test robot. v9 patch includes: . Simplify lm_expire_lock API by (1) remove the 'testonly' flag and (2) specifying return value as true/false to indicate whether conflict was succesfully resolved. . Rework nfsd4_fl_expire_lock to mark client with NFSD4_DESTROY_COURTESY_CLIENT then tell the laundromat to expire the client in the background. . Add a spinlock in nfs4_client to synchronize access to the NFSD4_COURTESY_CLIENT and NFSD4_DESTROY_COURTESY_CLIENT flag to handle race conditions when resolving lock and share reservation conflict. . Courtesy client that was marked as NFSD4_DESTROY_COURTESY_CLIENT are now consisdered 'dead', waiting for the laundromat to expire it. This client is no longer allowed to use its states if it reconnects before the laundromat finishes expiring the client. For v4.1 client, the detection is done in the processing of the SEQUENCE op and returns NFS4ERR_BAD_SESSION to force the client to re-establish new clientid and session. For v4.0 client, the detection is done in the processing of the RENEW and state-related ops and return NFS4ERR_EXPIRE to force the client to re-establish new clientid. v10 patch includes: Resolve deadlock in v9 by avoiding getting cl_client and cl_cs_lock together. The laundromat needs to determine whether the expired client has any state and also has no blockers on its locks. Both of these conditions are allowed to change after the laundromat transits an expired client to courtesy client. When this happens, the laundromat will detect it on the next run and and expire the courtesy client. Remove client persistent record before marking it as COURTESY_CLIENT and add client persistent record before clearing the COURTESY_CLIENT flag to allow the courtesy client to transist to normal client to continue to use its state. Lock/delegation/share reversation conflict with courtesy client is resolved by marking the courtesy client as DESTROY_COURTESY_CLIENT, effectively disable it, then allow the current request to proceed immediately. Courtesy client marked as DESTROY_COURTESY_CLIENT is not allowed to reconnect to reuse itsstate. It is expired by the laundromat asynchronously in the background. Move processing of expired clients from nfs4_laudromat to a separate function, nfs4_get_client_reaplist, that creates the reaplist and also to process courtesy clients. Update Documentation/filesystems/locking.rst to include new lm_lock_conflict call. Modify leases_conflict to call lm_breaker_owns_lease only if there is real conflict. This is to allow the lock manager to resolve the delegation conflict if possible. v11 patch includes: Add comment for lm_lock_conflict callback. Replace static const courtesy_client_expiry with macro. Remove courtesy_clnt argument from find_in_sessionid_hashtbl. Callers use nfs4_client->cl_cs_client boolean to determined if it's the courtesy client and take appropriate actions. Rename NFSD4_COURTESY_CLIENT and NFSD4_DESTROY_COURTESY_CLIENT with NFSD4_CLIENT_COURTESY and NFSD4_CLIENT_DESTROY_COURTESY. v12 patch includes: Remove unnecessary comment in nfs4_get_client_reaplist. Replace nfs4_client->cl_cs_client boolean with NFSD4_CLIENT_COURTESY_CLNT flag. Remove courtesy_clnt argument from find_client_in_id_table and find_clp_in_name_tree. Callers use NFSD4_CLIENT_COURTESY_CLNT to determined if it's the courtesy client and take appropriate actions. v13 patch includes: Merge with 5.17-rc3. Cleanup Documentation/filesystems/locking.rst: replace i_lock with flc_lock, update API's that use flc_lock. Rename lm_lock_conflict to lm_lock_expired(). Remove comment of lm_lock_expired API in lock_manager_operations. Same information is in patch description. Update commit messages of 4/4. Add some comment for NFSD4_CLIENT_COURTESY_CLNT. Add nfsd4_discard_courtesy_clnt() to eliminate duplicate code of discarding courtesy client; setting NFSD4_DESTROY_COURTESY_CLIENT. v14 patch includes: . merge with Chuck's public for-next branch. . remove courtesy_client_expiry, use client's last renew time. . simplify comment of nfs4_check_access_deny_bmap. . add comment about race condition in nfs4_get_client_reaplist. . add list_del when walking cslist in nfs4_get_client_reaplist. . remove duplicate INIT_LIST_HEAD(&reaplist) from nfs4_laundromat . Modify find_confirmed_client and find_confirmed_client_by_name to detect courtesy client and destroy it. . refactor lookup_clientid to use find_client_in_id_table directly instead of find_confirmed_client. . refactor nfsd4_setclientid to call find_clp_in_name_tree directly instead of find_confirmed_client_by_name. . remove comment of NFSD4_CLIENT_COURTESY. . replace NFSD4_CLIENT_DESTROY_COURTESY with NFSD4_CLIENT_EXPIRED. . replace NFSD4_CLIENT_COURTESY_CLNT with NFSD4_CLIENT_RECONNECTED. v15 patch includes: . add helper locks_has_blockers_locked in fs.h to check for lock blockers . rename nfs4_conflict_clients to nfs4_resolve_deny_conflicts_locked . update nfs4_upgrade_open() to handle courtesy clients. . add helper nfs4_check_and_expire_courtesy_client and nfs4_is_courtesy_client_expired to deduplicate some code. . update nfs4_anylock_blocker: . replace list_for_each_entry_safe with list_for_each_entry . break nfs4_anylock_blocker into 2 smaller functions. . update nfs4_get_client_reaplist: . remove unnecessary commets . acquire cl_cs_lock before setting NFSD4_CLIENT_COURTESY flag . update client_info_show to show 'time since last renew: 00:00:38' instead of 'seconds from last renew: 38'.
