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Fix a race between cache_enter() and cache_revlookup().

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This commit is contained in:
ad 2020-03-23 18:37:30 +00:00
parent 395a577cab
commit 18a510d734
1 changed files with 27 additions and 30 deletions
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53
sys/kern/vfs_cache.c
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@ -1,4 +1,4 @@
/* $NetBSD: vfs_cache.c,v 1.129 2020/03/23 18:33:43 ad Exp $ */ /* $NetBSD: vfs_cache.c,v 1.130 2020/03/23 18:37:30 ad Exp $ */
/*- /*-
* Copyright (c) 2008, 2019, 2020 The NetBSD Foundation, Inc. * Copyright (c) 2008, 2019, 2020 The NetBSD Foundation, Inc.
@ -172,7 +172,7 @@
*/ */
#include <sys/cdefs.h> #include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: vfs_cache.c,v 1.129 2020/03/23 18:33:43 ad Exp $"); __KERNEL_RCSID(0, "$NetBSD: vfs_cache.c,v 1.130 2020/03/23 18:37:30 ad Exp $");
#define __NAMECACHE_PRIVATE #define __NAMECACHE_PRIVATE
#ifdef _KERNEL_OPT #ifdef _KERNEL_OPT
@ -896,16 +896,20 @@ cache_enter(struct vnode *dvp, struct vnode *vp,
ncp = kmem_alloc(sz, KM_SLEEP); ncp = kmem_alloc(sz, KM_SLEEP);
} }
/* Fill in cache info. */ /*
* Fill in cache info. For negative hits, save the ISWHITEOUT flag
* so we can restore it later when the cache entry is used again.
*/
ncp->nc_vp = vp;
ncp->nc_dvp = dvp; ncp->nc_dvp = dvp;
ncp->nc_key = cache_key(name, namelen); ncp->nc_key = cache_key(name, namelen);
ncp->nc_nlen = namelen; ncp->nc_nlen = namelen;
ncp->nc_whiteout = ((cnflags & ISWHITEOUT) != 0);
memcpy(ncp->nc_name, name, namelen); memcpy(ncp->nc_name, name, namelen);
/* /*
* Insert to the directory. Concurrent lookups in the same * Insert to the directory. Concurrent lookups may race for a cache
* directory may race for a cache entry. There can also be hash * entry. If there's a entry there already, purge it.
* value collisions. If there's a entry there already, purge it.
*/ */
rw_enter(&dvi->vi_nc_lock, RW_WRITER); rw_enter(&dvi->vi_nc_lock, RW_WRITER);
oncp = rb_tree_insert_node(&dvi->vi_nc_tree, ncp); oncp = rb_tree_insert_node(&dvi->vi_nc_tree, ncp);
@ -920,16 +924,23 @@ cache_enter(struct vnode *dvp, struct vnode *vp,
KASSERT(oncp == ncp); KASSERT(oncp == ncp);
} }
/* Then insert to the vnode. */
if (vp == NULL) {
/* /*
* For negative hits, save the ISWHITEOUT flag so we can * With the directory lock still held, insert to the tail of the
* restore it later when the cache entry is used again. * ACTIVE LRU list (new) and with the LRU lock held take the to
* opportunity to incrementally balance the lists.
*/ */
ncp->nc_vp = NULL; mutex_enter(&cache_lru_lock);
ncp->nc_whiteout = ((cnflags & ISWHITEOUT) != 0); ncp->nc_lrulist = LRU_ACTIVE;
} else { cache_lru.count[LRU_ACTIVE]++;
/* Partially sort the per-vnode list: dots go to back. */ TAILQ_INSERT_TAIL(&cache_lru.list[LRU_ACTIVE], ncp, nc_lru);
cache_deactivate();
mutex_exit(&cache_lru_lock);
/*
* Finally, insert to the vnode, and unlock. Partially sort the
* per-vnode list: dots go to back.
*/
if (vp != NULL) {
vnode_impl_t *vi = VNODE_TO_VIMPL(vp); vnode_impl_t *vi = VNODE_TO_VIMPL(vp);
rw_enter(&vi->vi_nc_listlock, RW_WRITER); rw_enter(&vi->vi_nc_listlock, RW_WRITER);
if ((namelen == 1 && name[0] == '.') || if ((namelen == 1 && name[0] == '.') ||
@ -939,21 +950,7 @@ cache_enter(struct vnode *dvp, struct vnode *vp,
TAILQ_INSERT_HEAD(&vi->vi_nc_list, ncp, nc_list); TAILQ_INSERT_HEAD(&vi->vi_nc_list, ncp, nc_list);
} }
rw_exit(&vi->vi_nc_listlock); rw_exit(&vi->vi_nc_listlock);
ncp->nc_vp = vp;
ncp->nc_whiteout = false;
} }
/*
* Finally, insert to the tail of the ACTIVE LRU list (new) and
* with the LRU lock held take the to opportunity to incrementally
* balance the lists.
*/
mutex_enter(&cache_lru_lock);
ncp->nc_lrulist = LRU_ACTIVE;
cache_lru.count[LRU_ACTIVE]++;
TAILQ_INSERT_TAIL(&cache_lru.list[LRU_ACTIVE], ncp, nc_lru);
cache_deactivate();
mutex_exit(&cache_lru_lock);
rw_exit(&dvi->vi_nc_lock); rw_exit(&dvi->vi_nc_lock);
} }