Author: rmacklem
Date: Wed Jan 27 15:22:20 2010
New Revision: 203072
URL: http://svn.freebsd.org/changeset/base/203072
Log:
Fix a race that can occur when nfs nfsiod threads are being created.
Without this patch it was possible for a different thread that calls
nfs_asyncio() to snitch a newly created nfsiod thread that was
intended for another caller of nfs_asyncio(), because the nfs_iod_mtx
mutex was unlocked while the new nfsiod thread was created. This patch
labels the newly created nfsiod, so that it is not taken by another
caller of nfs_asyncio(). This is believed to fix the problem reported
on the freebsd-stable email list under the subject:
FreeBSD NFS client/Linux NFS server issue.
Tested by: to DOT my DOT trociny AT gmail DOT com
Reviewed by: jhb
MFC after: 2 weeks
Modified:
head/sys/nfsclient/nfs.h
head/sys/nfsclient/nfs_bio.c
head/sys/nfsclient/nfs_nfsiod.c
head/sys/nfsclient/nfs_subs.c
head/sys/nfsclient/nfs_vnops.c
head/sys/nfsclient/nfsnode.h
Modified: head/sys/nfsclient/nfs.h
==============================================================================
--- head/sys/nfsclient/nfs.h Wed Jan 27 14:54:48 2010 (r203071)
+++ head/sys/nfsclient/nfs.h Wed Jan 27 15:22:20 2010 (r203072)
@@ -252,7 +252,7 @@ int nfs_writerpc(struct vnode *, struct
int nfs_commit(struct vnode *vp, u_quad_t offset, int cnt,
struct ucred *cred, struct thread *td);
int nfs_readdirrpc(struct vnode *, struct uio *, struct ucred *);
-int nfs_nfsiodnew(void);
+int nfs_nfsiodnew(int);
int nfs_asyncio(struct nfsmount *, struct buf *, struct ucred *, struct
thread *);
int nfs_doio(struct vnode *, struct buf *, struct ucred *, struct thread *);
void nfs_doio_directwrite (struct buf *);
Modified: head/sys/nfsclient/nfs_bio.c
==============================================================================
--- head/sys/nfsclient/nfs_bio.c Wed Jan 27 14:54:48 2010
(r203071)
+++ head/sys/nfsclient/nfs_bio.c Wed Jan 27 15:22:20 2010
(r203072)
@@ -1377,7 +1377,7 @@ again:
* Find a free iod to process this request.
*/
for (iod = 0; iod < nfs_numasync; iod++)
- if (nfs_iodwant[iod]) {
+ if (nfs_iodwant[iod] == NFSIOD_AVAILABLE) {
gotiod = TRUE;
break;
}
@@ -1386,7 +1386,7 @@ again:
* Try to create one if none are free.
*/
if (!gotiod) {
- iod = nfs_nfsiodnew();
+ iod = nfs_nfsiodnew(1);
if (iod != -1)
gotiod = TRUE;
}
@@ -1398,7 +1398,7 @@ again:
*/
NFS_DPF(ASYNCIO, ("nfs_asyncio: waking iod %d for mount %p\n",
iod, nmp));
- nfs_iodwant[iod] = NULL;
+ nfs_iodwant[iod] = NFSIOD_NOT_AVAILABLE;
nfs_iodmount[iod] = nmp;
nmp->nm_bufqiods++;
wakeup(&nfs_iodwant[iod]);
Modified: head/sys/nfsclient/nfs_nfsiod.c
==============================================================================
--- head/sys/nfsclient/nfs_nfsiod.c Wed Jan 27 14:54:48 2010
(r203071)
+++ head/sys/nfsclient/nfs_nfsiod.c Wed Jan 27 15:22:20 2010
(r203072)
@@ -113,7 +113,7 @@ sysctl_iodmin(SYSCTL_HANDLER_ARGS)
* than the new minimum, create some more.
*/
for (i = nfs_iodmin - nfs_numasync; i > 0; i--)
- nfs_nfsiodnew();
+ nfs_nfsiodnew(0);
out:
mtx_unlock(&nfs_iod_mtx);
return (0);
@@ -147,7 +147,7 @@ sysctl_iodmax(SYSCTL_HANDLER_ARGS)
*/
iod = nfs_numasync - 1;
for (i = 0; i < nfs_numasync - nfs_iodmax; i++) {
- if (nfs_iodwant[iod])
+ if (nfs_iodwant[iod] == NFSIOD_AVAILABLE)
wakeup(&nfs_iodwant[iod]);
iod--;
}
@@ -160,7 +160,7 @@ SYSCTL_PROC(_vfs_nfs, OID_AUTO, iodmax,
"Max number of nfsiod kthreads");
int
-nfs_nfsiodnew(void)
+nfs_nfsiodnew(int set_iodwant)
{
int error, i;
int newiod;
@@ -176,12 +176,17 @@ nfs_nfsiodnew(void)
}
if (newiod == -1)
return (-1);
+ if (set_iodwant > 0)
+ nfs_iodwant[i] = NFSIOD_CREATED_FOR_NFS_ASYNCIO;
mtx_unlock(&nfs_iod_mtx);
error = kproc_create(nfssvc_iod, nfs_asyncdaemon + i, NULL, RFHIGHPID,
0, "nfsiod %d", newiod);
mtx_lock(&nfs_iod_mtx);
- if (error)
+ if (error) {
+ if (set_iodwant > 0)
+ nfs_iodwant[i] = NFSIOD_NOT_AVAILABLE;
return (-1);
+ }
nfs_numasync++;
return (newiod);
}
@@ -199,7 +204,7 @@ nfsiod_setup(void *dummy)
nfs_iodmin = NFS_MAXASYNCDAEMON;
for (i = 0; i < nfs_iodmin; i++) {
- error = nfs_nfsiodnew();
+ error = nfs_nfsiodnew(0);
if (error == -1)
panic("nfsiod_setup: nfs_nfsiodnew failed");
}
@@ -236,7 +241,8 @@ nfssvc_iod(void *instance)
goto finish;
if (nmp)
nmp->nm_bufqiods--;
- nfs_iodwant[myiod] = curthread->td_proc;
+ if (nfs_iodwant[myiod] == NFSIOD_NOT_AVAILABLE)
+ nfs_iodwant[myiod] = NFSIOD_AVAILABLE;
nfs_iodmount[myiod] = NULL;
/*
* Always keep at least nfs_iodmin kthreads.
@@ -303,7 +309,7 @@ finish:
nfs_asyncdaemon[myiod] = 0;
if (nmp)
nmp->nm_bufqiods--;
- nfs_iodwant[myiod] = NULL;
+ nfs_iodwant[myiod] = NFSIOD_NOT_AVAILABLE;
nfs_iodmount[myiod] = NULL;
/* Someone may be waiting for the last nfsiod to terminate. */
if (--nfs_numasync == 0)
Modified: head/sys/nfsclient/nfs_subs.c
==============================================================================
--- head/sys/nfsclient/nfs_subs.c Wed Jan 27 14:54:48 2010
(r203071)
+++ head/sys/nfsclient/nfs_subs.c Wed Jan 27 15:22:20 2010
(r203072)
@@ -347,7 +347,7 @@ nfs_init(struct vfsconf *vfsp)
nfs_ticks = 1;
/* Ensure async daemons disabled */
for (i = 0; i < NFS_MAXASYNCDAEMON; i++) {
- nfs_iodwant[i] = NULL;
+ nfs_iodwant[i] = NFSIOD_NOT_AVAILABLE;
nfs_iodmount[i] = NULL;
}
nfs_nhinit(); /* Init the nfsnode table */
@@ -375,7 +375,7 @@ nfs_uninit(struct vfsconf *vfsp)
mtx_lock(&nfs_iod_mtx);
nfs_iodmax = 0;
for (i = 0; i < nfs_numasync; i++)
- if (nfs_iodwant[i])
+ if (nfs_iodwant[i] == NFSIOD_AVAILABLE)
wakeup(&nfs_iodwant[i]);
/* The last nfsiod to exit will wake us up when nfs_numasync hits 0 */
while (nfs_numasync)
Modified: head/sys/nfsclient/nfs_vnops.c
==============================================================================
--- head/sys/nfsclient/nfs_vnops.c Wed Jan 27 14:54:48 2010
(r203071)
+++ head/sys/nfsclient/nfs_vnops.c Wed Jan 27 15:22:20 2010
(r203072)
@@ -212,7 +212,7 @@ static int nfs_renameit(struct vnode *sd
* Global variables
*/
struct mtx nfs_iod_mtx;
-struct proc *nfs_iodwant[NFS_MAXASYNCDAEMON];
+enum nfsiod_state nfs_iodwant[NFS_MAXASYNCDAEMON];
struct nfsmount *nfs_iodmount[NFS_MAXASYNCDAEMON];
int nfs_numasync = 0;
vop_advlock_t *nfs_advlock_p = nfs_dolock;
Modified: head/sys/nfsclient/nfsnode.h
==============================================================================
--- head/sys/nfsclient/nfsnode.h Wed Jan 27 14:54:48 2010
(r203071)
+++ head/sys/nfsclient/nfsnode.h Wed Jan 27 15:22:20 2010
(r203072)
@@ -177,10 +177,23 @@ struct nfsnode {
#define NFS_TIMESPEC_COMPARE(T1, T2) (((T1)->tv_sec != (T2)->tv_sec) ||
((T1)->tv_nsec != (T2)->tv_nsec))
/*
+ * NFS iod threads can be in one of these three states once spawned.
+ * NFSIOD_NOT_AVAILABLE - Cannot be assigned an I/O operation at this time.
+ * NFSIOD_AVAILABLE - Available to be assigned an I/O operation.
+ * NFSIOD_CREATED_FOR_NFS_ASYNCIO - Newly created for nfs_asyncio() and
+ * will be used by the thread that called nfs_asyncio().
+ */
+enum nfsiod_state {
+ NFSIOD_NOT_AVAILABLE = 0,
+ NFSIOD_AVAILABLE = 1,
+ NFSIOD_CREATED_FOR_NFS_ASYNCIO = 2,
+};
+
+/*
* Queue head for nfsiod's
*/
extern TAILQ_HEAD(nfs_bufq, buf) nfs_bufq;
-extern struct proc *nfs_iodwant[NFS_MAXASYNCDAEMON];
+extern enum nfsiod_state nfs_iodwant[NFS_MAXASYNCDAEMON];
extern struct nfsmount *nfs_iodmount[NFS_MAXASYNCDAEMON];
#if defined(_KERNEL)
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