svn commit: r190533 - in head/sys: kern sys
Alexander Kabaev
kan at FreeBSD.org
Sun Mar 29 14:25:41 PDT 2009
Author: kan
Date: Sun Mar 29 21:25:40 2009
New Revision: 190533
URL: http://svn.freebsd.org/changeset/base/190533
Log:
Replace v_dd vnode pointer with v_cache_dd pointer to struct namecache
in directory vnodes. Allow namecache dotdot entry to be created pointing
from child vnode to parent vnode if no existing links in opposite
direction exist. Use direct link from parent to child for dotdot lookups
otherwise.
This restores more efficient dotdot caching in NFS filesystems which
was lost when vnodes stoppped being type stable.
Reviewed by: kib
Modified:
head/sys/kern/vfs_cache.c
head/sys/kern/vfs_subr.c
head/sys/sys/vnode.h
Modified: head/sys/kern/vfs_cache.c
==============================================================================
--- head/sys/kern/vfs_cache.c Sun Mar 29 21:17:08 2009 (r190532)
+++ head/sys/kern/vfs_cache.c Sun Mar 29 21:25:40 2009 (r190533)
@@ -187,7 +187,8 @@ static MALLOC_DEFINE(M_VFSCACHE, "vfscac
/*
* Flags in namecache.nc_flag
*/
-#define NCF_WHITE 1
+#define NCF_WHITE 0x01
+#define NCF_ISDOTDOT 0x02
#ifdef DIAGNOSTIC
/*
@@ -292,14 +293,20 @@ cache_zap(ncp)
CTR2(KTR_VFS, "cache_zap(%p) vp %p", ncp, ncp->nc_vp);
vp = NULL;
LIST_REMOVE(ncp, nc_hash);
- LIST_REMOVE(ncp, nc_src);
- if (LIST_EMPTY(&ncp->nc_dvp->v_cache_src)) {
- vp = ncp->nc_dvp;
- numcachehv--;
+ if (ncp->nc_flag & NCF_ISDOTDOT) {
+ if (ncp == ncp->nc_dvp->v_cache_dd)
+ ncp->nc_dvp->v_cache_dd = NULL;
+ } else {
+ LIST_REMOVE(ncp, nc_src);
+ if (LIST_EMPTY(&ncp->nc_dvp->v_cache_src)) {
+ vp = ncp->nc_dvp;
+ numcachehv--;
+ }
}
if (ncp->nc_vp) {
TAILQ_REMOVE(&ncp->nc_vp->v_cache_dst, ncp, nc_dst);
- ncp->nc_vp->v_dd = NULL;
+ if (ncp == ncp->nc_vp->v_cache_dd)
+ ncp->nc_vp->v_cache_dd = NULL;
} else {
TAILQ_REMOVE(&ncneg, ncp, nc_dst);
numneg--;
@@ -358,11 +365,18 @@ retry_wlocked:
}
if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
dotdothits++;
- if (dvp->v_dd == NULL ||
- (cnp->cn_flags & MAKEENTRY) == 0) {
+ if (dvp->v_cache_dd == NULL)
+ goto unlock;
+ if ((cnp->cn_flags & MAKEENTRY) == 0) {
+ if (dvp->v_cache_dd->nc_flag & NCF_ISDOTDOT)
+ cache_zap(dvp->v_cache_dd);
+ dvp->v_cache_dd = NULL;
goto unlock;
}
- *vpp = dvp->v_dd;
+ if (dvp->v_cache_dd->nc_flag & NCF_ISDOTDOT)
+ *vpp = dvp->v_cache_dd->nc_vp;
+ else
+ *vpp = dvp->v_cache_dd->nc_dvp;
CTR3(KTR_VFS, "cache_lookup(%p, %s) found %p via ..",
dvp, cnp->cn_nameptr, *vpp);
goto success;
@@ -522,6 +536,7 @@ cache_enter(dvp, vp, cnp)
struct namecache *ncp, *n2;
struct nchashhead *ncpp;
u_int32_t hash;
+ int flag;
int hold;
int zap;
int len;
@@ -539,23 +554,33 @@ cache_enter(dvp, vp, cnp)
if (numcache >= desiredvnodes * 2)
return;
+ flag = 0;
if (cnp->cn_nameptr[0] == '.') {
- if (cnp->cn_namelen == 1) {
+ if (cnp->cn_namelen == 1)
return;
- }
- /*
- * For dotdot lookups only cache the v_dd pointer if the
- * directory has a link back to its parent via v_cache_dst.
- * Without this an unlinked directory would keep a soft
- * reference to its parent which could not be NULLd at
- * cache_purge() time.
- */
if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
CACHE_WLOCK();
- if (!TAILQ_EMPTY(&dvp->v_cache_dst))
- dvp->v_dd = vp;
+ /*
+ * If dotdot entry already exists, just retarget it
+ * to new parent vnode, otherwise continue with new
+ * namecache entry allocation.
+ */
+ if ((ncp = dvp->v_cache_dd) != NULL) {
+ if (ncp->nc_flag & NCF_ISDOTDOT) {
+ KASSERT(ncp->nc_dvp == dvp,
+ ("wrong isdotdot parent"));
+ TAILQ_REMOVE(&ncp->nc_vp->v_cache_dst,
+ ncp, nc_dst);
+ TAILQ_INSERT_HEAD(&vp->v_cache_dst,
+ ncp, nc_dst);
+ ncp->nc_vp = vp;
+ CACHE_WUNLOCK();
+ return;
+ }
+ }
+ dvp->v_cache_dd = NULL;
CACHE_WUNLOCK();
- return;
+ flag = NCF_ISDOTDOT;
}
}
@@ -569,6 +594,7 @@ cache_enter(dvp, vp, cnp)
ncp = cache_alloc(cnp->cn_namelen);
ncp->nc_vp = vp;
ncp->nc_dvp = dvp;
+ ncp->nc_flag = flag;
len = ncp->nc_nlen = cnp->cn_namelen;
hash = fnv_32_buf(cnp->cn_nameptr, len, FNV1_32_INIT);
bcopy(cnp->cn_nameptr, ncp->nc_name, len);
@@ -591,14 +617,34 @@ cache_enter(dvp, vp, cnp)
}
}
+ /*
+ * See if we are trying to add .. entry, but some other lookup
+ * has populated v_cache_dd pointer already.
+ */
+ if (flag == NCF_ISDOTDOT && dvp->v_cache_dd != NULL) {
+ CACHE_WUNLOCK();
+ cache_free(ncp);
+ return;
+ }
+
numcache++;
if (!vp) {
numneg++;
- ncp->nc_flag = cnp->cn_flags & ISWHITEOUT ? NCF_WHITE : 0;
+ if (cnp->cn_flags & ISWHITEOUT)
+ ncp->nc_flag |= NCF_WHITE;
} else if (vp->v_type == VDIR) {
- vp->v_dd = dvp;
+ if (flag == NCF_ISDOTDOT) {
+ KASSERT(dvp->v_cache_dd == NULL,
+ ("dangling v_cache_dd"));
+ dvp->v_cache_dd = ncp;
+ } else {
+ if ((n2 = vp->v_cache_dd) != NULL &&
+ (n2->nc_flag & NCF_ISDOTDOT) != 0)
+ cache_zap(n2);
+ vp->v_cache_dd = ncp;
+ }
} else {
- vp->v_dd = NULL;
+ vp->v_cache_dd = NULL;
}
/*
@@ -606,11 +652,14 @@ cache_enter(dvp, vp, cnp)
* within the cache entries table.
*/
LIST_INSERT_HEAD(ncpp, ncp, nc_hash);
- if (LIST_EMPTY(&dvp->v_cache_src)) {
- hold = 1;
- numcachehv++;
+ if (flag != NCF_ISDOTDOT) {
+ if (LIST_EMPTY(&dvp->v_cache_src)) {
+ hold = 1;
+ numcachehv++;
+ }
+ LIST_INSERT_HEAD(&dvp->v_cache_src, ncp, nc_src);
}
- LIST_INSERT_HEAD(&dvp->v_cache_src, ncp, nc_src);
+
/*
* If the entry is "negative", we place it into the
* "negative" cache queue, otherwise, we place it into the
@@ -665,7 +714,12 @@ cache_purge(vp)
cache_zap(LIST_FIRST(&vp->v_cache_src));
while (!TAILQ_EMPTY(&vp->v_cache_dst))
cache_zap(TAILQ_FIRST(&vp->v_cache_dst));
- vp->v_dd = NULL;
+ if (vp->v_cache_dd != NULL) {
+ KASSERT(vp->v_cache_dd->nc_flag & NCF_ISDOTDOT,
+ ("lost dotdot link"));
+ cache_zap(vp->v_cache_dd);
+ }
+ KASSERT(vp->v_cache_dd == NULL, ("incomplete purge"));
CACHE_WUNLOCK();
}
@@ -995,9 +1049,10 @@ vn_fullpath1(struct thread *td, struct v
error = ENOTDIR;
break;
}
- ncp = TAILQ_FIRST(&vp->v_cache_dst);
+ TAILQ_FOREACH(ncp, &vp->v_cache_dst, nc_dst)
+ if ((ncp->nc_flag & NCF_ISDOTDOT) == 0)
+ break;
if (ncp != NULL) {
- MPASS(vp->v_dd == NULL || ncp->nc_dvp == vp->v_dd);
buflen -= ncp->nc_nlen;
for (i = ncp->nc_nlen - 1; i >= 0 && bp != buf; i--)
*--bp = ncp->nc_name[i];
@@ -1047,8 +1102,10 @@ vn_commname(struct vnode *vp, char *buf,
int l;
CACHE_RLOCK();
- ncp = TAILQ_FIRST(&vp->v_cache_dst);
- if (!ncp) {
+ TAILQ_FOREACH(ncp, &vp->v_cache_dst, nc_dst)
+ if ((ncp->nc_flag & NCF_ISDOTDOT) == 0)
+ break;
+ if (ncp == NULL) {
CACHE_RUNLOCK();
return (ENOENT);
}
Modified: head/sys/kern/vfs_subr.c
==============================================================================
--- head/sys/kern/vfs_subr.c Sun Mar 29 21:17:08 2009 (r190532)
+++ head/sys/kern/vfs_subr.c Sun Mar 29 21:25:40 2009 (r190533)
@@ -860,6 +860,7 @@ vdestroy(struct vnode *vp)
VNASSERT(bo->bo_dirty.bv_root == NULL, vp, ("dirtyblkroot not NULL"));
VNASSERT(TAILQ_EMPTY(&vp->v_cache_dst), vp, ("vp has namecache dst"));
VNASSERT(LIST_EMPTY(&vp->v_cache_src), vp, ("vp has namecache src"));
+ VNASSERT(vp->v_cache_dd == NULL, vp, ("vp has namecache for .."));
VI_UNLOCK(vp);
#ifdef MAC
mac_vnode_destroy(vp);
Modified: head/sys/sys/vnode.h
==============================================================================
--- head/sys/sys/vnode.h Sun Mar 29 21:17:08 2009 (r190532)
+++ head/sys/sys/vnode.h Sun Mar 29 21:25:40 2009 (r190533)
@@ -135,7 +135,7 @@ struct vnode {
*/
LIST_HEAD(, namecache) v_cache_src; /* c Cache entries from us */
TAILQ_HEAD(, namecache) v_cache_dst; /* c Cache entries to us */
- struct vnode *v_dd; /* c .. vnode */
+ struct namecache *v_cache_dd; /* c Cache entry for .. vnode */
/*
* clustering stuff
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