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NFSv4: fairly test all delegations on a SEQ4_ revocation 

When the client is required to use TEST_STATEID to discover which
delegation(s) have been revoked, it may continually test delegations at the
head of the list if the server continues to be unsatisfied and send
SEQ4_STATUS_RECALLABLE_STATE_REVOKED.  For a large number of delegations
this behavior is prone to live-lock because the client may never be able to
test and free revoked state at the end of the list since the
SEQ4_STATUS_RECALLABLE_STATE_REVOKED will cause us to flag delegations at
the head of the list to be tested.  This problem is further exacerbated by
the state manager's willingness to be scheduled out on a busy system while
testing the list of delegations.

Keep a generation counter for each attempt to test all delegations, and
skip delegations that have already been tested in the current pass.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Tested-by: Torkil Svensgaard <torkil@drcmr.dk>
Tested-by: Ruben Vestergaard <rubenv@drcmr.dk>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
This commit is contained in:
Benjamin Coddington 2023-08-24 14:52:19 -04:00 committed by Trond Myklebust
parent 59464b262f
commit a9b8d90f87
3 changed files with 8 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
fs/nfs/delegation.c
View File

@ -448,6 +448,7 @@ int nfs_inode_set_delegation(struct inode *inode, const struct cred *cred,
delegation->cred = get_cred(cred);
delegation->inode = inode;
delegation->flags = 1<<NFS_DELEGATION_REFERENCED;
delegation->test_gen = 0;
spin_lock_init(&delegation->lock);
spin_lock(&clp->cl_lock);
@ -1294,6 +1295,8 @@ static int nfs_server_reap_expired_delegations(struct nfs_server *server,
struct inode *inode;
const struct cred *cred;
nfs4_stateid stateid;
unsigned long gen = ++server->delegation_gen;
restart:
rcu_read_lock();
restart_locked:
@ -1303,7 +1306,8 @@ restart_locked:
test_bit(NFS_DELEGATION_RETURNING,
&delegation->flags) ||
test_bit(NFS_DELEGATION_TEST_EXPIRED,
&delegation->flags) == 0)
&delegation->flags) == 0 ||
delegation->test_gen == gen)
continue;
inode = nfs_delegation_grab_inode(delegation);
if (inode == NULL)
@ -1312,6 +1316,7 @@ restart_locked:
cred = get_cred_rcu(delegation->cred);
nfs4_stateid_copy(&stateid, &delegation->stateid);
spin_unlock(&delegation->lock);
delegation->test_gen = gen;
clear_bit(NFS_DELEGATION_TEST_EXPIRED, &delegation->flags);
rcu_read_unlock();
nfs_delegation_test_free_expired(inode, &stateid, cred);

1
fs/nfs/delegation.h
View File

@ -21,6 +21,7 @@ struct nfs_delegation {
fmode_t type;
unsigned long pagemod_limit;
__u64 change_attr;
unsigned long test_gen;
unsigned long flags;
refcount_t refcount;
spinlock_t lock;

1
include/linux/nfs_fs_sb.h
View File

@ -239,6 +239,7 @@ struct nfs_server {
struct list_head delegations;
struct list_head ss_copies;
unsigned long delegation_gen;
unsigned long mig_gen;
unsigned long mig_status;
#define NFS_MIG_IN_TRANSITION (1)