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Restructure vdrain_vrele(). While it is not possible for another thread

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to lock this vnodes v_interlock -> vdrain_lock another vnode sharing the
v_interlock may lock this order.
While here, restore fstrans_start_nowait arg to FSTRANS_LAZY.

Fixes a deadlock seen recently on some pbulk environments.
This commit is contained in:
hannken 2016-12-20 10:02:21 +00:00
parent ca3357623e
commit 0d2ece78cb
1 changed files with 11 additions and 12 deletions
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23
sys/kern/vfs_vnode.c
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@ -1,4 +1,4 @@
/* $NetBSD: vfs_vnode.c,v 1.63 2016/12/14 15:49:35 hannken Exp $ */
/* $NetBSD: vfs_vnode.c,v 1.64 2016/12/20 10:02:21 hannken Exp $ */
/*-
* Copyright (c) 1997-2011 The NetBSD Foundation, Inc.
@ -156,7 +156,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: vfs_vnode.c,v 1.63 2016/12/14 15:49:35 hannken Exp $");
__KERNEL_RCSID(0, "$NetBSD: vfs_vnode.c,v 1.64 2016/12/20 10:02:21 hannken Exp $");
#include <sys/param.h>
#include <sys/kernel.h>
@ -502,26 +502,25 @@ vdrain_vrele(vnode_t *vp)
KASSERT(mutex_owned(&vdrain_lock));
/*
* Safe to take v_interlock -- no other thread will
* lock v_interlock -> vdrain_lock as usecount > 0.
*/
mutex_enter(vp->v_interlock);
mp = vp->v_mount;
if (fstrans_start_nowait(mp, FSTRANS_SHARED) != 0) {
mutex_exit(vp->v_interlock);
if (fstrans_start_nowait(mp, FSTRANS_LAZY) != 0)
return;
}
/* First put the vnode back onto its lru list. */
/*
* First remove the vnode from the vrele list.
* Put it on the last lru list, the last vrele()
* will put it back onto the right list before
* its v_usecount reaches zero.
*/
KASSERT(node->vi_lrulisthd == &lru_vrele_list);
TAILQ_REMOVE(node->vi_lrulisthd, node, vi_lrulist);
node->vi_lrulisthd = lru_which(vp);
node->vi_lrulisthd = &lru_hold_list;
TAILQ_INSERT_TAIL(node->vi_lrulisthd, node, vi_lrulist);
vdrain_retry = true;
mutex_exit(&vdrain_lock);
mutex_enter(vp->v_interlock);
vrelel(vp, 0);
fstrans_done(mp);