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vfs: avoid spurious vref/vrele for absolute lookups

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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.

Reviewed by:	kib
This commit is contained in:
Mateusz Guzik 2015-07-09 15:06:58 +00:00
parent a03f1b2970
commit d19ba50e12
1 changed files with 46 additions and 24 deletions
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70
sys/kern/vfs_lookup.c
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@ -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);