Author: rmacklem
Date: Sat Aug 28 21:41:18 2010
New Revision: 211951
URL: http://svn.freebsd.org/changeset/base/211951
Log:
The timer routine in the experimental NFS server did not acquire
the correct mutex when checking nfsv4root_lock. Although this
could be fixed by adding mutex lock/unlock calls, zack.kirsch at
isilon.com suggested a better fix that uses a non-blocking
acquisition of a reference count on nfsv4root_lock. This fix
allows the weird NFSLOCKSTATE(); NFSUNLOCKSTATE(); synchronization
to be deleted. This patch applies this fix.
Tested by: zack.kirsch at isilon.com
MFC after: 2 weeks
Modified:
head/sys/fs/nfs/nfs_commonsubs.c
head/sys/fs/nfs/nfs_var.h
head/sys/fs/nfsserver/nfs_nfsdsocket.c
head/sys/fs/nfsserver/nfs_nfsdstate.c
Modified: head/sys/fs/nfs/nfs_commonsubs.c
==============================================================================
--- head/sys/fs/nfs/nfs_commonsubs.c Sat Aug 28 21:15:00 2010
(r211950)
+++ head/sys/fs/nfs/nfs_commonsubs.c Sat Aug 28 21:41:18 2010
(r211951)
@@ -1824,6 +1824,21 @@ nfsv4_getref(struct nfsv4lock *lp, int *
}
/*
+ * Get a reference as above, but return failure instead of sleeping if
+ * an exclusive lock is held.
+ */
+APPLESTATIC int
+nfsv4_getref_nonblock(struct nfsv4lock *lp)
+{
+
+ if ((lp->nfslock_lock & NFSV4LOCK_LOCK) != 0)
+ return (0);
+
+ lp->nfslock_usecnt++;
+ return (1);
+}
+
+/*
* Test for a lock. Return 1 if locked, 0 otherwise.
*/
APPLESTATIC int
Modified: head/sys/fs/nfs/nfs_var.h
==============================================================================
--- head/sys/fs/nfs/nfs_var.h Sat Aug 28 21:15:00 2010 (r211950)
+++ head/sys/fs/nfs/nfs_var.h Sat Aug 28 21:41:18 2010 (r211951)
@@ -251,6 +251,7 @@ int nfsv4_lock(struct nfsv4lock *, int,
void nfsv4_unlock(struct nfsv4lock *, int);
void nfsv4_relref(struct nfsv4lock *);
void nfsv4_getref(struct nfsv4lock *, int *, void *);
+int nfsv4_getref_nonblock(struct nfsv4lock *);
int nfsv4_testlock(struct nfsv4lock *);
int nfsrv_mtostr(struct nfsrv_descript *, char *, int);
int nfsrv_checkutf8(u_int8_t *, int);
Modified: head/sys/fs/nfsserver/nfs_nfsdsocket.c
==============================================================================
--- head/sys/fs/nfsserver/nfs_nfsdsocket.c Sat Aug 28 21:15:00 2010
(r211950)
+++ head/sys/fs/nfsserver/nfs_nfsdsocket.c Sat Aug 28 21:41:18 2010
(r211951)
@@ -533,8 +533,6 @@ nfsrvd_compound(struct nfsrv_descript *n
NFSV4ROOTLOCKMUTEXPTR);
NFSUNLOCKV4ROOTMUTEX();
if (igotlock) {
- NFSLOCKSTATE(); /* to avoid a race with */
- NFSUNLOCKSTATE(); /* nfsrv_servertimer() */
/*
* If I got the lock, I can update the stable storage file.
* Done when the grace period is over or a client has long
Modified: head/sys/fs/nfsserver/nfs_nfsdstate.c
==============================================================================
--- head/sys/fs/nfsserver/nfs_nfsdstate.c Sat Aug 28 21:15:00 2010
(r211950)
+++ head/sys/fs/nfsserver/nfs_nfsdstate.c Sat Aug 28 21:41:18 2010
(r211951)
@@ -164,8 +164,6 @@ nfsrv_setclient(struct nfsrv_descript *n
NFSV4ROOTLOCKMUTEXPTR);
} while (!igotlock);
NFSUNLOCKV4ROOTMUTEX();
- NFSLOCKSTATE(); /* to avoid a race with */
- NFSUNLOCKSTATE(); /* nfsrv_servertimer() */
/*
* Search for a match in the client list.
@@ -416,8 +414,6 @@ nfsrv_getclient(nfsquad_t clientid, int
NFSV4ROOTLOCKMUTEXPTR);
} while (!igotlock);
NFSUNLOCKV4ROOTMUTEX();
- NFSLOCKSTATE(); /* to avoid a race with */
- NFSUNLOCKSTATE(); /* nfsrv_servertimer() */
} else if (opflags != CLOPS_RENEW) {
NFSLOCKSTATE();
}
@@ -547,8 +543,6 @@ nfsrv_adminrevoke(struct nfsd_clid *revo
NFSV4ROOTLOCKMUTEXPTR);
} while (!igotlock);
NFSUNLOCKV4ROOTMUTEX();
- NFSLOCKSTATE(); /* to avoid a race with */
- NFSUNLOCKSTATE(); /* nfsrv_servertimer() */
/*
* Search for a match in the client list.
@@ -824,11 +818,8 @@ nfsrv_dumplocks(vnode_t vp, struct nfsd_
/*
* Server timer routine. It can scan any linked list, so long
- * as it holds the spin lock and there is no exclusive lock on
+ * as it holds the spin/mutex lock and there is no exclusive lock on
* nfsv4rootfs_lock.
- * Must be called by a kernel thread and not a timer interrupt,
- * so that it only runs when the nfsd threads are sleeping on a
- * uniprocessor and uses the State spin lock for an SMP system.
* (For OpenBSD, a kthread is ok. For FreeBSD, I think it is ok
* to do this from a callout, since the spin locks work. For
* Darwin, I'm not sure what will work correctly yet.)
@@ -839,7 +830,7 @@ nfsrv_servertimer(void)
{
struct nfsclient *clp, *nclp;
struct nfsstate *stp, *nstp;
- int i;
+ int got_ref, i;
/*
* Make sure nfsboottime is set. This is used by V3 as well
@@ -867,13 +858,14 @@ nfsrv_servertimer(void)
}
/*
- * Return now if an nfsd thread has the exclusive lock on
- * nfsv4rootfs_lock. The dirty trick here is that we have
- * the spin lock already and the nfsd threads do a:
- * NFSLOCKSTATE, NFSUNLOCKSTATE after getting the exclusive
- * lock, so they won't race with code after this check.
+ * Try and get a reference count on the nfsv4rootfs_lock so that
+ * no nfsd thread can acquire an exclusive lock on it before this
+ * call is done. If it is already exclusively locked, just return.
*/
- if (nfsv4rootfs_lock.nfslock_lock & NFSV4LOCK_LOCK) {
+ NFSLOCKV4ROOTMUTEX();
+ got_ref = nfsv4_getref_nonblock(&nfsv4rootfs_lock);
+ NFSUNLOCKV4ROOTMUTEX();
+ if (got_ref == 0) {
NFSUNLOCKSTATE();
return;
}
@@ -945,6 +937,9 @@ nfsrv_servertimer(void)
}
}
NFSUNLOCKSTATE();
+ NFSLOCKV4ROOTMUTEX();
+ nfsv4_relref(&nfsv4rootfs_lock);
+ NFSUNLOCKV4ROOTMUTEX();
}
/*
@@ -4224,8 +4219,6 @@ nfsrv_clientconflict(struct nfsclient *c
NFSV4ROOTLOCKMUTEXPTR);
} while (!gotlock);
NFSUNLOCKV4ROOTMUTEX();
- NFSLOCKSTATE(); /* to avoid a race with */
- NFSUNLOCKSTATE(); /* nfsrv_servertimer() */
*haslockp = 1;
NFSVOPLOCK(vp, LK_EXCLUSIVE | LK_RETRY, p);
return (1);
@@ -4390,8 +4383,6 @@ nfsrv_delegconflict(struct nfsstate *stp
NFSV4ROOTLOCKMUTEXPTR);
} while (!gotlock);
NFSUNLOCKV4ROOTMUTEX();
- NFSLOCKSTATE(); /* to avoid a race with */
- NFSUNLOCKSTATE(); /* nfsrv_servertimer() */
*haslockp = 1;
NFSVOPLOCK(vp, LK_EXCLUSIVE | LK_RETRY, p);
return (-1);
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