Re: [PATCH RFC v9 0/2] nfsd: Initial implementation of NFSv4 Courteous Server

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 




On 1/12/22 10:59 AM, J. Bruce Fields wrote:
Could you look back over previous comments?  I notice there's a couple
unaddressed (circular locking dependency, Documentation/filesystems/).

I think v9 addresses the circular locking dependency. I will update the
Documentation/filesystems/locking.rst in v10.


I agree with Chuck that we don't need to reschedule the laundromat, it's
OK if it takes longer to get around to cleaning up a dead client.

Yes, it is now implemented for lock conflict and share reservation
resolution. I'm doing the same for delegation conflict.

-Dai


--b.

On Mon, Jan 10, 2022 at 10:50:51AM -0800, Dai Ngo wrote:
Hi Bruce, Chuck

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.

The v2 patch includes the following:

. 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 re-connects, causing the client to keep sending
   BCTS requests to server.

The v3 patch includes the following:

. 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.

The 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.

The v5 patch includes:

. fix recursive locking of file_rwsem from posix_lock_file.

. retest with LOCKDEP enabled.

The 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.

The 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.

The v8 patch includes:

. Fix warning in nfsd4_fl_expire_lock reported by test robot.

The V9 patch include:

. 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
   re-connects 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.



[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [NTFS 3]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [NTFS 3]     [Samba]     [Device Mapper]     [CEPH Development]

  Powered by Linux