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When union_allocvp() finds a node being cleaned out and the caller holds

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a lock, ignore the node and continue.  To allow the cleaning to succeed
the current threadmust make progress.
For a brief time the cache may contain more than one vnode referring to
a lower node.

Don't unlock the hash mutex if getnewvnode fails -- we don't hold it.
This commit is contained in:
hannken 2011-11-25 11:19:10 +00:00
parent f045c4d360
commit ea1a52c704
1 changed files with 26 additions and 4 deletions
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30
sys/fs/union/union_subr.c
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@ -1,4 +1,4 @@
/* $NetBSD: union_subr.c,v 1.54 2011/11/23 19:39:11 hannken Exp $ */
/* $NetBSD: union_subr.c,v 1.55 2011/11/25 11:19:10 hannken Exp $ */
/*
* Copyright (c) 1994
@ -72,7 +72,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: union_subr.c,v 1.54 2011/11/23 19:39:11 hannken Exp $");
__KERNEL_RCSID(0, "$NetBSD: union_subr.c,v 1.55 2011/11/25 11:19:10 hannken Exp $");
#include <sys/param.h>
#include <sys/systm.h>
@ -404,6 +404,18 @@ loop:
lflag = LK_EXCLUSIVE;
vp = UNIONTOV(un);
mutex_enter(vp->v_interlock);
/*
* If this node being cleaned out and our caller
* holds a lock, then ignore it and continue. To
* allow the cleaning to succeed the current thread
* must make progress. For a brief time the cache
* may contain more than one vnode referring to
* a lower node.
*/
if ((vp->v_iflag & VI_XLOCK) != 0 && lflag == 0) {
mutex_exit(vp->v_interlock);
continue;
}
mutex_exit(&uhash_lock);
if (vget(vp, lflag))
goto loop;
@ -484,7 +496,7 @@ found:
if (lowervp)
vrele(lowervp);
goto out;
return error;
}
if (docache) {
@ -493,6 +505,17 @@ found:
if (un1->un_lowervp == lowervp &&
un1->un_uppervp == uppervp &&
UNIONTOV(un1)->v_mount == mp) {
vp = UNIONTOV(un1);
mutex_enter(vp->v_interlock);
/*
* Ignore nodes being cleaned out.
* See the cache lookup above.
*/
if ((vp->v_iflag & VI_XLOCK) != 0) {
mutex_exit(vp->v_interlock);
continue;
}
mutex_exit(vp->v_interlock);
/*
* Another thread beat us, push back freshly
* allocated vnode and retry.
@ -569,7 +592,6 @@ found:
if (xlowervp)
vrele(xlowervp);
out:
if (docache)
mutex_exit(&uhash_lock);