Module Name: src
Committed By: hannken
Date: Sat Nov 23 13:46:22 UTC 2013
Modified Files:
src/sys/kern: vfs_vnode.c
src/sys/sys: vnode.h
Log Message:
Replace VI_INACTNOW and VI_INACTREDO with a new flag VI_CHANGING that gets
set while a vnode changes state from active to inactive or from active
or inactive to clean and protects "vclean(); vrelel()" and "vrelel()"
against "vget()".
Presented on tech-kern.
To generate a diff of this commit:
cvs rdiff -u -r1.25 -r1.26 src/sys/kern/vfs_vnode.c
cvs rdiff -u -r1.240 -r1.241 src/sys/sys/vnode.h
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/vfs_vnode.c
diff -u src/sys/kern/vfs_vnode.c:1.25 src/sys/kern/vfs_vnode.c:1.26
--- src/sys/kern/vfs_vnode.c:1.25 Thu Nov 7 09:48:34 2013
+++ src/sys/kern/vfs_vnode.c Sat Nov 23 13:46:22 2013
@@ -1,4 +1,4 @@
-/* $NetBSD: vfs_vnode.c,v 1.25 2013/11/07 09:48:34 hannken Exp $ */
+/* $NetBSD: vfs_vnode.c,v 1.26 2013/11/23 13:46:22 hannken Exp $ */
/*-
* Copyright (c) 1997-2011 The NetBSD Foundation, Inc.
@@ -116,7 +116,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_vnode.c,v 1.25 2013/11/07 09:48:34 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_vnode.c,v 1.26 2013/11/23 13:46:22 hannken Exp $");
#define _VFS_VNODE_PRIVATE
@@ -145,6 +145,7 @@ __KERNEL_RCSID(0, "$NetBSD: vfs_vnode.c,
/* Flags to vrelel. */
#define VRELEL_ASYNC_RELE 0x0001 /* Always defer to vrele thread. */
+#define VRELEL_CHANGING_SET 0x0002 /* VI_CHANGING set by caller. */
u_int numvnodes __cacheline_aligned;
@@ -323,8 +324,10 @@ try_nextlist:
* before doing this.
*/
vp->v_usecount = 1;
+ KASSERT((vp->v_iflag & VI_CHANGING) == 0);
+ vp->v_iflag |= VI_CHANGING;
vclean(vp);
- vrelel(vp, 0);
+ vrelel(vp, VRELEL_CHANGING_SET);
fstrans_done(mp);
return 0;
@@ -476,10 +479,10 @@ vremfree(vnode_t *vp)
*
* => Should be called with v_interlock held.
*
- * If VI_XLOCK is set, the vnode is being eliminated in vgone()/vclean().
+ * If VI_CHANGING is set, the vnode may be eliminated in vgone()/vclean().
* In that case, we cannot grab the vnode, so the process is awakened when
* the transition is completed, and an error returned to indicate that the
- * vnode is no longer usable (e.g. changed to a new file system type).
+ * vnode is no longer usable.
*/
int
vget(vnode_t *vp, int flags)
@@ -502,31 +505,16 @@ vget(vnode_t *vp, int flags)
}
/*
- * If the vnode is in the process of being cleaned out for
- * another use, we wait for the cleaning to finish and then
- * return failure. Cleaning is determined by checking if
- * the VI_XLOCK flag is set.
+ * If the vnode is in the process of changing state we wait
+ * for the change to complete and take care not to return
+ * a clean vnode.
*/
- if ((vp->v_iflag & VI_XLOCK) != 0) {
+ if ((vp->v_iflag & VI_CHANGING) != 0) {
if ((flags & LK_NOWAIT) != 0) {
vrelel(vp, 0);
return EBUSY;
}
- vwait(vp, VI_XLOCK);
- vrelel(vp, 0);
- return ENOENT;
- }
-
- if ((vp->v_iflag & VI_INACTNOW) != 0) {
- /*
- * if it's being desactived, wait for it to complete.
- * Make sure to not return a clean vnode.
- */
- if ((flags & LK_NOWAIT) != 0) {
- vrelel(vp, 0);
- return EBUSY;
- }
- vwait(vp, VI_INACTNOW);
+ vwait(vp, VI_CHANGING);
if ((vp->v_iflag & VI_CLEAN) != 0) {
vrelel(vp, 0);
return ENOENT;
@@ -605,7 +593,11 @@ vrelel(vnode_t *vp, int flags)
* and unlock.
*/
if (vtryrele(vp)) {
- vp->v_iflag |= VI_INACTREDO;
+ if ((flags & VRELEL_CHANGING_SET) != 0) {
+ KASSERT((vp->v_iflag & VI_CHANGING) != 0);
+ vp->v_iflag &= ~VI_CHANGING;
+ cv_broadcast(&vp->v_cv);
+ }
mutex_exit(vp->v_interlock);
return;
}
@@ -614,6 +606,10 @@ vrelel(vnode_t *vp, int flags)
}
KASSERT((vp->v_iflag & VI_XLOCK) == 0);
+ if ((flags & VRELEL_CHANGING_SET) == 0) {
+ KASSERT((vp->v_iflag & VI_CHANGING) == 0);
+ vp->v_iflag |= VI_CHANGING;
+ }
#ifdef DIAGNOSTIC
if ((vp->v_type == VBLK || vp->v_type == VCHR) &&
@@ -626,10 +622,8 @@ vrelel(vnode_t *vp, int flags)
* If not clean, deactivate the vnode, but preserve
* our reference across the call to VOP_INACTIVE().
*/
-retry:
if ((vp->v_iflag & VI_CLEAN) == 0) {
recycle = false;
- vp->v_iflag |= VI_INACTNOW;
/*
* XXX This ugly block can be largely eliminated if
@@ -644,11 +638,8 @@ retry:
defer = true;
} else if (curlwp == vrele_lwp) {
/*
- * We have to try harder. But we can't sleep
- * with VI_INACTNOW as vget() may be waiting on it.
+ * We have to try harder.
*/
- vp->v_iflag &= ~(VI_INACTREDO|VI_INACTNOW);
- cv_broadcast(&vp->v_cv);
mutex_exit(vp->v_interlock);
error = vn_lock(vp, LK_EXCLUSIVE);
if (error != 0) {
@@ -663,10 +654,12 @@ retry:
*/
if (__predict_false(vtryrele(vp))) {
VOP_UNLOCK(vp);
+ KASSERT((vp->v_iflag & VI_CHANGING) != 0);
+ vp->v_iflag &= ~VI_CHANGING;
+ cv_broadcast(&vp->v_cv);
mutex_exit(vp->v_interlock);
return;
}
- vp->v_iflag |= VI_INACTNOW;
mutex_exit(vp->v_interlock);
defer = false;
} else if ((vp->v_iflag & VI_LAYER) != 0) {
@@ -678,7 +671,6 @@ retry:
defer = true;
} else {
/* If we can't acquire the lock, then defer. */
- vp->v_iflag &= ~VI_INACTREDO;
mutex_exit(vp->v_interlock);
error = vn_lock(vp, LK_EXCLUSIVE | LK_NOWAIT);
if (error != 0) {
@@ -695,7 +687,8 @@ retry:
* clean it here. We donate it our last reference.
*/
KASSERT(mutex_owned(vp->v_interlock));
- vp->v_iflag &= ~VI_INACTNOW;
+ KASSERT((vp->v_iflag & VI_CHANGING) != 0);
+ vp->v_iflag &= ~VI_CHANGING;
mutex_enter(&vrele_lock);
TAILQ_INSERT_TAIL(&vrele_list, vp, v_freelist);
if (++vrele_pending > (desiredvnodes >> 8))
@@ -718,21 +711,14 @@ retry:
*/
VOP_INACTIVE(vp, &recycle);
mutex_enter(vp->v_interlock);
- vp->v_iflag &= ~VI_INACTNOW;
- cv_broadcast(&vp->v_cv);
if (!recycle) {
if (vtryrele(vp)) {
+ KASSERT((vp->v_iflag & VI_CHANGING) != 0);
+ vp->v_iflag &= ~VI_CHANGING;
+ cv_broadcast(&vp->v_cv);
mutex_exit(vp->v_interlock);
return;
}
-
- /*
- * If we grew another reference while
- * VOP_INACTIVE() was underway, retry.
- */
- if ((vp->v_iflag & VI_INACTREDO) != 0) {
- goto retry;
- }
}
/* Take care of space accounting. */
@@ -757,6 +743,9 @@ retry:
if (atomic_dec_uint_nv(&vp->v_usecount) != 0) {
/* Gained another reference while being reclaimed. */
+ KASSERT((vp->v_iflag & VI_CHANGING) != 0);
+ vp->v_iflag &= ~VI_CHANGING;
+ cv_broadcast(&vp->v_cv);
mutex_exit(vp->v_interlock);
return;
}
@@ -788,6 +777,9 @@ retry:
}
TAILQ_INSERT_TAIL(vp->v_freelisthd, vp, v_freelist);
mutex_exit(&vnode_free_list_lock);
+ KASSERT((vp->v_iflag & VI_CHANGING) != 0);
+ vp->v_iflag &= ~VI_CHANGING;
+ cv_broadcast(&vp->v_cv);
mutex_exit(vp->v_interlock);
}
}
@@ -798,7 +790,7 @@ vrele(vnode_t *vp)
KASSERT((vp->v_iflag & VI_MARKER) == 0);
- if ((vp->v_iflag & VI_INACTNOW) == 0 && vtryrele(vp)) {
+ if (vtryrele(vp)) {
return;
}
mutex_enter(vp->v_interlock);
@@ -814,7 +806,7 @@ vrele_async(vnode_t *vp)
KASSERT((vp->v_iflag & VI_MARKER) == 0);
- if ((vp->v_iflag & VI_INACTNOW) == 0 && vtryrele(vp)) {
+ if (vtryrele(vp)) {
return;
}
mutex_enter(vp->v_interlock);
@@ -1058,8 +1050,10 @@ vrecycle(vnode_t *vp, kmutex_t *inter_lk
}
vremfree(vp);
vp->v_usecount = 1;
+ KASSERT((vp->v_iflag & VI_CHANGING) == 0);
+ vp->v_iflag |= VI_CHANGING;
vclean(vp);
- vrelel(vp, 0);
+ vrelel(vp, VRELEL_CHANGING_SET);
return 1;
}
@@ -1082,8 +1076,8 @@ vrevoke(vnode_t *vp)
return;
} else if (vp->v_type != VBLK && vp->v_type != VCHR) {
atomic_inc_uint(&vp->v_usecount);
- vclean(vp);
- vrelel(vp, 0);
+ mutex_exit(vp->v_interlock);
+ vgone(vp);
return;
} else {
dev = vp->v_rdev;
@@ -1092,9 +1086,7 @@ vrevoke(vnode_t *vp)
}
while (spec_node_lookup_by_dev(type, dev, &vq) == 0) {
- mutex_enter(vq->v_interlock);
- vclean(vq);
- vrelel(vq, 0);
+ vgone(vq);
}
}
@@ -1107,8 +1099,11 @@ vgone(vnode_t *vp)
{
mutex_enter(vp->v_interlock);
+ if ((vp->v_iflag & VI_CHANGING) != 0)
+ vwait(vp, VI_CHANGING);
+ vp->v_iflag |= VI_CHANGING;
vclean(vp);
- vrelel(vp, 0);
+ vrelel(vp, VRELEL_CHANGING_SET);
}
/*
Index: src/sys/sys/vnode.h
diff -u src/sys/sys/vnode.h:1.240 src/sys/sys/vnode.h:1.241
--- src/sys/sys/vnode.h:1.240 Thu Nov 7 09:48:34 2013
+++ src/sys/sys/vnode.h Sat Nov 23 13:46:22 2013
@@ -1,4 +1,4 @@
-/* $NetBSD: vnode.h,v 1.240 2013/11/07 09:48:34 hannken Exp $ */
+/* $NetBSD: vnode.h,v 1.241 2013/11/23 13:46:22 hannken Exp $ */
/*-
* Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -206,8 +206,7 @@ typedef struct vnode vnode_t;
#define VI_LOCKSHARE 0x00040000 /* v_interlock is shared */
#define VI_CLEAN 0x00080000 /* has been reclaimed */
#ifdef _VFS_VNODE_PRIVATE
-#define VI_INACTREDO 0x00200000 /* need to redo VOP_INACTIVE() */
-#define VI_INACTNOW 0x00800000 /* VOP_INACTIVE() in progress */
+#define VI_CHANGING 0x00100000 /* vnode changes state */
#endif /* _VFS_VNODE_PRIVATE */
/*
@@ -218,8 +217,7 @@ typedef struct vnode vnode_t;
#define VNODE_FLAGBITS \
"\20\1ROOT\2SYSTEM\3ISTTY\4MAPPED\5MPSAFE\6LOCKSWORK\11TEXT\12EXECMAP" \
"\13WRMAP\14WRMAPDIRTY\15XLOCK\17ONWORKLST\20MARKER" \
- "\22LAYER\24CLEAN\26INACTREDO" \
- "\30INACTNOW\31DIROP"
+ "\22LAYER\24CLEAN\25CHANGING\31DIROP"
#define VSIZENOTSET ((voff_t)-1)
