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[src/ad-namecache]: src/sys/kern Push the vnode locking in namei() about as f...
details: https://anonhg.NetBSD.org/src/rev/3d4b2e312fb5
branches: ad-namecache
changeset: 467178:3d4b2e312fb5
user: ad <ad%NetBSD.org@localhost>
date: Thu Jan 16 16:45:30 2020 +0000
description:
Push the vnode locking in namei() about as far back as it will go.
diffstat:
sys/kern/vfs_lookup.c | 306 ++++++++++++++++++++++++++++---------------------
1 files changed, 174 insertions(+), 132 deletions(-)
diffs (truncated from 601 to 300 lines):
diff -r d10792439afa -r 3d4b2e312fb5 sys/kern/vfs_lookup.c
--- a/sys/kern/vfs_lookup.c Tue Jan 14 11:08:01 2020 +0000
+++ b/sys/kern/vfs_lookup.c Thu Jan 16 16:45:30 2020 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: vfs_lookup.c,v 1.212 2019/07/18 09:39:40 hannken Exp $ */
+/* $NetBSD: vfs_lookup.c,v 1.212.4.1 2020/01/16 16:45:30 ad Exp $ */
/*
* Copyright (c) 1982, 1986, 1989, 1993
@@ -37,7 +37,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_lookup.c,v 1.212 2019/07/18 09:39:40 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_lookup.c,v 1.212.4.1 2020/01/16 16:45:30 ad Exp $");
#ifdef _KERNEL_OPT
#include "opt_magiclinks.h"
@@ -710,8 +710,6 @@
return ENOTDIR;
}
- vn_lock(startdir, LK_EXCLUSIVE | LK_RETRY);
-
*startdir_ret = startdir;
return 0;
}
@@ -749,15 +747,17 @@
size_t linklen;
int error;
- KASSERT(VOP_ISLOCKED(searchdir) == LK_EXCLUSIVE);
- KASSERT(VOP_ISLOCKED(foundobj) == LK_EXCLUSIVE);
if (ndp->ni_loopcnt++ >= MAXSYMLINKS) {
return ELOOP;
}
+
+ vn_lock(foundobj, LK_EXCLUSIVE | LK_RETRY);
if (foundobj->v_mount->mnt_flag & MNT_SYMPERM) {
error = VOP_ACCESS(foundobj, VEXEC, cnp->cn_cred);
- if (error != 0)
+ if (error != 0) {
+ VOP_UNLOCK(foundobj);
return error;
+ }
}
/* FUTURE: fix this to not use a second buffer */
@@ -771,6 +771,7 @@
auio.uio_resid = MAXPATHLEN;
UIO_SETUP_SYSSPACE(&auio);
error = VOP_READLINK(foundobj, &auio, cnp->cn_cred);
+ VOP_UNLOCK(foundobj);
if (error) {
PNBUF_PUT(cp);
return error;
@@ -807,14 +808,11 @@
/* we're now starting from the beginning of the buffer again */
cnp->cn_nameptr = ndp->ni_pnbuf;
- /* must unlock this before relocking searchdir */
- VOP_UNLOCK(foundobj);
-
/*
* Check if root directory should replace current directory.
*/
if (ndp->ni_pnbuf[0] == '/') {
- vput(searchdir);
+ vrele(searchdir);
/* Keep absolute symbolic links inside emulation root */
searchdir = ndp->ni_erootdir;
if (searchdir == NULL ||
@@ -825,7 +823,6 @@
searchdir = ndp->ni_rootdir;
}
vref(searchdir);
- vn_lock(searchdir, LK_EXCLUSIVE | LK_RETRY);
while (cnp->cn_nameptr[0] == '/') {
cnp->cn_nameptr++;
ndp->ni_pathlen--;
@@ -833,7 +830,6 @@
}
*newsearchdir_ret = searchdir;
- KASSERT(VOP_ISLOCKED(searchdir) == LK_EXCLUSIVE);
return 0;
}
@@ -933,19 +929,20 @@
lookup_once(struct namei_state *state,
struct vnode *searchdir,
struct vnode **newsearchdir_ret,
- struct vnode **foundobj_ret)
+ struct vnode **foundobj_ret,
+ bool *newsearchdir_locked_ret)
{
struct vnode *tmpvn; /* scratch vnode */
struct vnode *foundobj; /* result */
struct mount *mp; /* mount table entry */
struct lwp *l = curlwp;
+ bool searchdir_locked = false;
int error;
struct componentname *cnp = state->cnp;
struct nameidata *ndp = state->ndp;
KASSERT(cnp == &ndp->ni_cnd);
- KASSERT(VOP_ISLOCKED(searchdir) == LK_EXCLUSIVE);
*newsearchdir_ret = searchdir;
/*
@@ -977,9 +974,7 @@
if (ndp->ni_rootdir != rootvnode) {
int retval;
- VOP_UNLOCK(searchdir);
retval = vn_isunder(searchdir, ndp->ni_rootdir, l);
- vn_lock(searchdir, LK_EXCLUSIVE | LK_RETRY);
if (!retval) {
/* Oops! We got out of jail! */
log(LOG_WARNING,
@@ -988,12 +983,11 @@
p->p_pid, kauth_cred_geteuid(l->l_cred),
p->p_comm);
/* Put us at the jail root. */
- vput(searchdir);
+ vrele(searchdir);
searchdir = NULL;
foundobj = ndp->ni_rootdir;
vref(foundobj);
vref(foundobj);
- vn_lock(foundobj, LK_EXCLUSIVE | LK_RETRY);
*newsearchdir_ret = foundobj;
*foundobj_ret = foundobj;
error = 0;
@@ -1006,18 +1000,19 @@
tmpvn = searchdir;
searchdir = searchdir->v_mount->mnt_vnodecovered;
vref(searchdir);
- vput(tmpvn);
- vn_lock(searchdir, LK_EXCLUSIVE | LK_RETRY);
+ vrele(tmpvn);
*newsearchdir_ret = searchdir;
}
}
/*
* We now have a segment name to search for, and a directory to search.
- * Our vnode state here is that "searchdir" is held and locked.
+ * Our vnode state here is that "searchdir" is held.
*/
unionlookup:
foundobj = NULL;
+ vn_lock(searchdir, LK_EXCLUSIVE | LK_RETRY);
+ searchdir_locked = true;
error = VOP_LOOKUP(searchdir, &foundobj, cnp);
if (error != 0) {
@@ -1034,7 +1029,7 @@
searchdir = searchdir->v_mount->mnt_vnodecovered;
vref(searchdir);
vput(tmpvn);
- vn_lock(searchdir, LK_EXCLUSIVE | LK_RETRY);
+ searchdir_locked = false;
*newsearchdir_ret = searchdir;
goto unionlookup;
}
@@ -1089,84 +1084,99 @@
}
/*
- * "searchdir" is locked and held, "foundobj" is held,
- * they may be the same vnode.
- */
- if (searchdir != foundobj) {
- if (cnp->cn_flags & ISDOTDOT)
- VOP_UNLOCK(searchdir);
- error = vn_lock(foundobj, LK_EXCLUSIVE);
- if (cnp->cn_flags & ISDOTDOT)
- vn_lock(searchdir, LK_EXCLUSIVE | LK_RETRY);
- if (error != 0) {
- vrele(foundobj);
- goto done;
- }
- }
-
- /*
- * Check to see if the vnode has been mounted on;
- * if so find the root of the mounted file system.
+ * Do an unlocked check to see if the vnode has been mounted on; if
+ * so find the root of the mounted file system.
*/
KASSERT(searchdir != NULL);
- while (foundobj->v_type == VDIR &&
- (mp = foundobj->v_mountedhere) != NULL &&
- (cnp->cn_flags & NOCROSSMOUNT) == 0) {
-
- KASSERT(searchdir != foundobj);
-
- error = vfs_busy(mp);
- if (error != 0) {
- vput(foundobj);
- goto done;
- }
- if (searchdir != NULL) {
- VOP_UNLOCK(searchdir);
- }
- vput(foundobj);
- error = VFS_ROOT(mp, &foundobj);
- vfs_unbusy(mp);
- if (error) {
- if (searchdir != NULL) {
- vn_lock(searchdir, LK_EXCLUSIVE | LK_RETRY);
+ if (foundobj->v_type == VDIR && foundobj->v_mountedhere != NULL &&
+ (cnp->cn_flags & NOCROSSMOUNT) == 0) {
+ /*
+ * "searchdir" is locked and held, "foundobj" is held,
+ * they may be the same vnode.
+ */
+ if (searchdir != foundobj) {
+ if (vn_lock(foundobj, LK_EXCLUSIVE | LK_NOWAIT) != 0) {
+ if (cnp->cn_flags & ISDOTDOT)
+ VOP_UNLOCK(searchdir);
+ error = vn_lock(foundobj, LK_EXCLUSIVE);
+ if (cnp->cn_flags & ISDOTDOT)
+ vn_lock(searchdir, LK_EXCLUSIVE | LK_RETRY);
+ if (error != 0) {
+ vrele(foundobj);
+ goto done;
+ }
}
- goto done;
}
- /*
- * Avoid locking vnodes from two filesystems because
- * it's prone to deadlock, e.g. when using puffs.
- * Also, it isn't a good idea to propagate slowness of
- * a filesystem up to the root directory. For now,
- * only handle the common case, where foundobj is
- * VDIR.
- *
- * In this case set searchdir to null to avoid using
- * it again. It is not correct to set searchdir ==
- * foundobj here as that will confuse the caller.
- * (See PR 40740.)
- */
- if (searchdir == NULL) {
- /* already been here once; do nothing further */
- } else if (foundobj->v_type == VDIR) {
- vrele(searchdir);
- *newsearchdir_ret = searchdir = NULL;
- } else {
- VOP_UNLOCK(foundobj);
- vn_lock(searchdir, LK_EXCLUSIVE | LK_RETRY);
- vn_lock(foundobj, LK_EXCLUSIVE | LK_RETRY);
+ while (foundobj->v_type == VDIR &&
+ (mp = foundobj->v_mountedhere) != NULL &&
+ (cnp->cn_flags & NOCROSSMOUNT) == 0) {
+
+ KASSERT(searchdir != foundobj);
+
+ error = vfs_busy(mp);
+ if (error != 0) {
+ vput(foundobj);
+ goto done;
+ }
+ if (searchdir != NULL) {
+ VOP_UNLOCK(searchdir);
+ searchdir_locked = false;
+ }
+ vput(foundobj);
+ error = VFS_ROOT(mp, &foundobj);
+ vfs_unbusy(mp);
+ if (error) {
+ if (searchdir != NULL) {
+ vn_lock(searchdir, LK_EXCLUSIVE | LK_RETRY);
+ searchdir_locked = true;
+ }
+ goto done;
+ }
+ /*
+ * Avoid locking vnodes from two filesystems because
+ * it's prone to deadlock, e.g. when using puffs.
+ * Also, it isn't a good idea to propagate slowness of
+ * a filesystem up to the root directory. For now,
+ * only handle the common case, where foundobj is
+ * VDIR.
+ *
+ * In this case set searchdir to null to avoid using
+ * it again. It is not correct to set searchdir ==
+ * foundobj here as that will confuse the caller.
+ * (See PR 47040.)
+ */
+ if (searchdir == NULL) {
+ /* already been here once; do nothing further */
+ } else if (foundobj->v_type == VDIR) {
+ vrele(searchdir);
+ *newsearchdir_ret = searchdir = NULL;
+ } else {
+ VOP_UNLOCK(foundobj);
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