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[src/trunk]: src/sys/fs/union Replace flag based union node locking with gene...
details: https://anonhg.NetBSD.org/src/rev/0aaa69551718
branches: trunk
changeset: 771464:0aaa69551718
user: hannken <hannken%NetBSD.org@localhost>
date: Mon Nov 21 18:29:22 2011 +0000
description:
Replace flag based union node locking with generic vnode lock, support
shared and nowait locks and protect un_uppervp and un_*sz with mutex.
Mark file system MPSAFE.
diffstat:
sys/fs/union/union.h | 47 +++++---
sys/fs/union/union_subr.c | 141 +++++++++++++++-------------
sys/fs/union/union_vfsops.c | 6 +-
sys/fs/union/union_vnops.c | 215 ++++++++++++++-----------------------------
4 files changed, 178 insertions(+), 231 deletions(-)
diffs (truncated from 933 to 300 lines):
diff -r ddaeb5166de7 -r 0aaa69551718 sys/fs/union/union.h
--- a/sys/fs/union/union.h Mon Nov 21 17:51:03 2011 +0000
+++ b/sys/fs/union/union.h Mon Nov 21 18:29:22 2011 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: union.h,v 1.21 2011/08/23 07:39:37 hannken Exp $ */
+/* $NetBSD: union.h,v 1.22 2011/11/21 18:29:22 hannken Exp $ */
/*
* Copyright (c) 1994 The Regents of the University of California.
@@ -105,28 +105,36 @@
#define UN_FILEMODE (S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH)
/*
- * A cache of vnode references
+ * A cache of vnode references.
+ * Lock requirements are:
+ *
+ * : stable
+ * c unheadlock[hash]
+ * l un_lock
+ * m un_lock or vnode lock to read, un_lock and
+ * exclusive vnode lock to write
+ * v vnode lock to read, exclusive vnode lock to write
+ *
+ * Lock order is vnode then un_lock.
*/
struct union_node {
- LIST_ENTRY(union_node) un_cache; /* Hash chain */
- struct vnode *un_vnode; /* Back pointer */
- struct vnode *un_uppervp; /* overlaying object */
- struct vnode *un_lowervp; /* underlying object */
- struct vnode *un_dirvp; /* Parent dir of uppervp */
- struct vnode *un_pvp; /* Parent vnode */
- char *un_path; /* saved component name */
- int un_hash; /* saved un_path hash value */
- int un_openl; /* # of opens on lowervp */
- unsigned int un_flags;
- struct vnode **un_dircache; /* cached union stack */
- off_t un_uppersz; /* size of upper object */
- off_t un_lowersz; /* size of lower object */
- lwp_t *un_lwp; /* DIAGNOSTIC only */
+ kmutex_t un_lock;
+ LIST_ENTRY(union_node) un_cache; /* c: Hash chain */
+ struct vnode *un_vnode; /* :: Back pointer */
+ struct vnode *un_uppervp; /* m: overlaying object */
+ struct vnode *un_lowervp; /* v: underlying object */
+ struct vnode *un_dirvp; /* v: Parent dir of uppervp */
+ struct vnode *un_pvp; /* v: Parent vnode */
+ char *un_path; /* v: saved component name */
+ int un_hash; /* v: saved un_path hash */
+ int un_openl; /* v: # of opens on lowervp */
+ unsigned int un_flags; /* v: node flags */
+ unsigned int un_cflags; /* c: cache flags */
+ struct vnode **un_dircache; /* v: cached union stack */
+ off_t un_uppersz; /* l: size of upper object */
+ off_t un_lowersz; /* l: size of lower object */
};
-#define UN_WANTED 0x01
-#define UN_LOCKED 0x02
-#define UN_ULOCK 0x04 /* Upper node is locked */
#define UN_KLOCK 0x08 /* Keep upper node locked on vput */
#define UN_CACHED 0x10 /* In union cache */
@@ -162,6 +170,7 @@
#define LOWERVP(vp) (VTOUNION(vp)->un_lowervp)
#define UPPERVP(vp) (VTOUNION(vp)->un_uppervp)
#define OTHERVP(vp) (UPPERVP(vp) ? UPPERVP(vp) : LOWERVP(vp))
+#define LOCKVP(vp) (UPPERVP(vp) ? UPPERVP(vp) : (vp))
extern int (**union_vnodeop_p)(void *);
diff -r ddaeb5166de7 -r 0aaa69551718 sys/fs/union/union_subr.c
--- a/sys/fs/union/union_subr.c Mon Nov 21 17:51:03 2011 +0000
+++ b/sys/fs/union/union_subr.c Mon Nov 21 18:29:22 2011 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: union_subr.c,v 1.52 2011/11/14 18:38:13 hannken Exp $ */
+/* $NetBSD: union_subr.c,v 1.53 2011/11/21 18:29:22 hannken Exp $ */
/*
* Copyright (c) 1994
@@ -72,7 +72,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: union_subr.c,v 1.52 2011/11/14 18:38:13 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: union_subr.c,v 1.53 2011/11/21 18:29:22 hannken Exp $");
#include <sys/param.h>
#include <sys/systm.h>
@@ -93,6 +93,7 @@
#include <uvm/uvm_extern.h>
#include <fs/union/union.h>
+#include <miscfs/genfs/genfs.h>
#include <miscfs/specfs/specdev.h>
/* must be power of two, otherwise change UNION_HASH() */
@@ -145,7 +146,9 @@
int nhash = UNION_HASH(uppervp, lowervp);
int docache = (lowervp != NULLVP || uppervp != NULLVP);
int lhash, uhash;
+ bool un_unlock;
+ KASSERT(VOP_ISLOCKED(UNIONTOV(un)) == LK_EXCLUSIVE);
/*
* Ensure locking is ordered from lower to higher
* to avoid deadlocks.
@@ -164,8 +167,8 @@
mutex_enter(&unheadlock[uhash]);
if (ohash != nhash || !docache) {
- if (un->un_flags & UN_CACHED) {
- un->un_flags &= ~UN_CACHED;
+ if (un->un_cflags & UN_CACHED) {
+ un->un_cflags &= ~UN_CACHED;
LIST_REMOVE(un, un_cache);
}
}
@@ -186,15 +189,30 @@
}
}
un->un_lowervp = lowervp;
+ mutex_enter(&un->un_lock);
un->un_lowersz = VNOVAL;
+ mutex_exit(&un->un_lock);
}
if (un->un_uppervp != uppervp) {
- if (un->un_uppervp)
+ if (un->un_uppervp) {
+ un_unlock = false;
vrele(un->un_uppervp);
+ } else
+ un_unlock = true;
+ mutex_enter(&un->un_lock);
un->un_uppervp = uppervp;
+ mutex_exit(&un->un_lock);
+ if (un_unlock) {
+ struct vop_unlock_args ap;
+
+ ap.a_vp = UNIONTOV(un);
+ genfs_unlock(&ap);
+ }
+ mutex_enter(&un->un_lock);
un->un_uppersz = VNOVAL;
+ mutex_exit(&un->un_lock);
/* Update union vnode interlock. */
if (uppervp != NULL) {
mutex_obj_hold(uppervp->v_interlock);
@@ -205,7 +223,7 @@
if (docache && (ohash != nhash)) {
LIST_INSERT_HEAD(&unhead[nhash], un, un_cache);
- un->un_flags |= UN_CACHED;
+ un->un_cflags |= UN_CACHED;
}
mutex_exit(&unheadlock[nhash]);
@@ -229,20 +247,23 @@
* Keep track of size changes in the underlying vnodes.
* If the size changes, then callback to the vm layer
* giving priority to the upper layer size.
+ *
+ * Mutex un_lock hold on entry and released on return.
*/
void
union_newsize(struct vnode *vp, off_t uppersz, off_t lowersz)
{
- struct union_node *un;
+ struct union_node *un = VTOUNION(vp);
off_t sz;
+ KASSERT(mutex_owned(&un->un_lock));
/* only interested in regular files */
if (vp->v_type != VREG) {
+ mutex_exit(&un->un_lock);
uvm_vnp_setsize(vp, 0);
return;
}
- un = VTOUNION(vp);
sz = VNOVAL;
if ((uppersz != VNOVAL) && (un->un_uppersz != uppersz)) {
@@ -256,6 +277,7 @@
if (sz == VNOVAL)
sz = un->un_lowersz;
}
+ mutex_exit(&un->un_lock);
if (sz != VNOVAL) {
#ifdef UNION_DIAGNOSTIC
@@ -319,6 +341,9 @@
int vflag, iflag;
int try;
+ if (uppervp)
+ KASSERT(VOP_ISLOCKED(uppervp) == LK_EXCLUSIVE);
+
if (uppervp == NULLVP && lowervp == NULLVP)
panic("union: unidentifiable allocation");
@@ -374,61 +399,33 @@
(un->un_uppervp == uppervp ||
un->un_uppervp == NULLVP) &&
(UNIONTOV(un)->v_mount == mp)) {
+ int lflag;
+
+ if (uppervp != NULL && (uppervp == dvp ||
+ uppervp == un->un_uppervp))
+ /* "." or already locked. */
+ lflag = 0;
+ else
+ lflag = LK_EXCLUSIVE;
vp = UNIONTOV(un);
mutex_enter(vp->v_interlock);
- if (vget(vp, 0)) {
- mutex_exit(&unheadlock[hash]);
+ mutex_exit(&unheadlock[hash]);
+ if (vget(vp, lflag))
goto loop;
- }
break;
}
}
- mutex_exit(&unheadlock[hash]);
-
if (un)
break;
+
+ mutex_exit(&unheadlock[hash]);
}
if (un) {
- /*
- * Obtain a lock on the union_node.
- * uppervp is locked, though un->un_uppervp
- * may not be. this doesn't break the locking
- * hierarchy since in the case that un->un_uppervp
- * is not yet locked it will be vrele'd and replaced
- * with uppervp.
- */
-
- if ((dvp != NULLVP) && (uppervp == dvp)) {
- /*
- * Access ``.'', so (un) will already
- * be locked. Since this process has
- * the lock on (uppervp) no other
- * process can hold the lock on (un).
- */
- KASSERT((un->un_flags & UN_LOCKED) != 0);
- KASSERT(curlwp == NULL || un->un_lwp == NULL ||
- un->un_lwp == curlwp);
- } else {
- if (un->un_flags & UN_LOCKED) {
- vrele(UNIONTOV(un));
- un->un_flags |= UN_WANTED;
- (void) tsleep(&un->un_flags, PINOD,
- "unionalloc", 0);
- goto loop;
- }
- un->un_flags |= UN_LOCKED;
-
- un->un_lwp = curlwp;
- }
-
- /*
- * At this point, the union_node is locked,
- * un->un_uppervp may not be locked, and uppervp
- * is locked or nil.
- */
-
+ KASSERT(VOP_ISLOCKED(UNIONTOV(un)) == LK_EXCLUSIVE);
+ KASSERT(uppervp == NULL ||
+ VOP_ISLOCKED(uppervp) == LK_EXCLUSIVE);
/*
* Save information about the upper layer.
*/
@@ -438,10 +435,8 @@
vrele(uppervp);
}
- if (un->un_uppervp) {
- un->un_flags |= UN_ULOCK;
+ if (un->un_uppervp)
un->un_flags &= ~UN_KLOCK;
- }
/*
* Save information about the lower layer.
@@ -536,6 +531,7 @@
spec_node_init(*vpp, rdev);
un = VTOUNION(*vpp);
+ mutex_init(&un->un_lock, MUTEX_DEFAULT, IPL_NONE);
un->un_vnode = *vpp;
un->un_uppervp = uppervp;
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