Date: Thu, 9 Jul 2015 00:07:09 +0200 From: Mateusz Guzik <mjguzik@gmail.com> To: Konstantin Belousov <kostikbel@gmail.com> Cc: rwatson@FreeBSD.org, freebsd-fs@freebsd.org, Mateusz Guzik <mjg@freebsd.org> Subject: [PATCH 2/4] vfs: avoid spurious vref/vrele for absolute lookups Message-ID: <1436393231-5831-3-git-send-email-mjguzik@gmail.com> In-Reply-To: <1436393231-5831-1-git-send-email-mjguzik@gmail.com> References: <20150707085857.GZ2080@kib.kiev.ua> <1436393231-5831-1-git-send-email-mjguzik@gmail.com>
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From: Mateusz Guzik <mjg@freebsd.org>
namei used to vref fd_cdir, which was immediatley vrele'd on entry to
the loop.
Check for absolute lookup and vref the right vnode the first time.
---
sys/kern/vfs_lookup.c | 70 +++++++++++++++++++++++++++++++++------------------
1 file changed, 46 insertions(+), 24 deletions(-)
diff --git a/sys/kern/vfs_lookup.c b/sys/kern/vfs_lookup.c
index 20f8e96..e434464 100644
--- a/sys/kern/vfs_lookup.c
+++ b/sys/kern/vfs_lookup.c
@@ -109,6 +109,27 @@ namei_cleanup_cnp(struct componentname *cnp)
#endif
}
+static int
+namei_handle_root(struct nameidata *ndp, struct vnode **dpp)
+{
+ struct componentname *cnp = &ndp->ni_cnd;
+
+ if (ndp->ni_strictrelative != 0) {
+#ifdef KTRACE
+ if (KTRPOINT(curthread, KTR_CAPFAIL))
+ ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
+#endif
+ return (ENOTCAPABLE);
+ }
+ while (*(cnp->cn_nameptr) == '/') {
+ cnp->cn_nameptr++;
+ ndp->ni_pathlen--;
+ }
+ *dpp = ndp->ni_rootdir;
+ VREF(*dpp);
+ return (0);
+}
+
/*
* Convert a pathname into a pointer to a locked vnode.
*
@@ -222,7 +243,18 @@ namei(struct nameidata *ndp)
AUDIT_ARG_UPATH2(td, ndp->ni_dirfd, cnp->cn_pnbuf);
dp = NULL;
- if (cnp->cn_pnbuf[0] != '/') {
+ cnp->cn_nameptr = cnp->cn_pnbuf;
+ if (cnp->cn_pnbuf[0] == '/') {
+ error = namei_handle_root(ndp, &dp);
+ FILEDESC_SUNLOCK(fdp);
+ if (error != 0) {
+ vrele(ndp->ni_rootdir);
+ if (ndp->ni_startdir != NULL)
+ vrele(ndp->ni_startdir);
+ namei_cleanup_cnp(cnp);
+ return (error);
+ }
+ } else {
if (ndp->ni_startdir != NULL) {
dp = ndp->ni_startdir;
error = 0;
@@ -276,29 +308,6 @@ namei(struct nameidata *ndp)
SDT_PROBE(vfs, namei, lookup, entry, dp, cnp->cn_pnbuf,
cnp->cn_flags, 0, 0);
for (;;) {
- /*
- * Check if root directory should replace current directory.
- * Done at start of translation and after symbolic link.
- */
- cnp->cn_nameptr = cnp->cn_pnbuf;
- if (*(cnp->cn_nameptr) == '/') {
- vrele(dp);
- if (ndp->ni_strictrelative != 0) {
-#ifdef KTRACE
- if (KTRPOINT(curthread, KTR_CAPFAIL))
- ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL);
-#endif
- vrele(ndp->ni_rootdir);
- namei_cleanup_cnp(cnp);
- return (ENOTCAPABLE);
- }
- while (*(cnp->cn_nameptr) == '/') {
- cnp->cn_nameptr++;
- ndp->ni_pathlen--;
- }
- dp = ndp->ni_rootdir;
- VREF(dp);
- }
ndp->ni_startdir = dp;
error = lookup(ndp);
if (error) {
@@ -375,6 +384,19 @@ namei(struct nameidata *ndp)
ndp->ni_pathlen += linklen;
vput(ndp->ni_vp);
dp = ndp->ni_dvp;
+ /*
+ * Check if root directory should replace current directory.
+ */
+ cnp->cn_nameptr = cnp->cn_pnbuf;
+ if (*(cnp->cn_nameptr) == '/') {
+ vrele(dp);
+ error = namei_handle_root(ndp, &dp);
+ if (error != 0) {
+ vrele(ndp->ni_rootdir);
+ namei_cleanup_cnp(cnp);
+ return (error);
+ }
+ }
}
vrele(ndp->ni_rootdir);
namei_cleanup_cnp(cnp);
--
2.4.5
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