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cache: add empty path support

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This avoids spurious drop offs as EMPTY is passed regardless of the
actual path name.

Pushign the work inside the lookup instead of just ignorign the flag
allows avoid checking for empty pathname for all other lookups.
This commit is contained in:
Mateusz Guzik 2021-09-26 15:00:24 +02:00
parent 46dd801acb
commit 7dd419cabc
3 changed files with 74 additions and 13 deletions
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2
sys/kern/kern_descrip.c
View File

@ -2903,7 +2903,7 @@ fgetvp_lookup_smr(int fd, struct nameidata *ndp, struct vnode **vpp, bool *fsear
return (EAGAIN);
*fsearch = ((fp->f_flag & FSEARCH) != 0);
vp = fp->f_vnode;
if (__predict_false(vp == NULL || vp->v_type != VDIR)) {
if (__predict_false(vp == NULL)) {
return (EAGAIN);
}
if (!filecaps_copy(&fde->fde_caps, &ndp->ni_filecaps, false)) {

67
sys/kern/vfs_cache.c
View File

@ -4176,9 +4176,9 @@ cache_fpl_terminated(struct cache_fpl *fpl)
#define CACHE_FPL_SUPPORTED_CN_FLAGS \
(NC_NOMAKEENTRY | NC_KEEPPOSENTRY | LOCKLEAF | LOCKPARENT | WANTPARENT | \
FAILIFEXISTS | FOLLOW | LOCKSHARED | SAVENAME | SAVESTART | WILLBEDIR | \
ISOPEN | NOMACCHECK | AUDITVNODE1 | AUDITVNODE2 | NOCAPCHECK | OPENREAD | \
OPENWRITE)
FAILIFEXISTS | FOLLOW | EMPTYPATH | LOCKSHARED | SAVENAME | SAVESTART | \
WILLBEDIR | ISOPEN | NOMACCHECK | AUDITVNODE1 | AUDITVNODE2 | NOCAPCHECK | \
OPENREAD | OPENWRITE)
#define CACHE_FPL_INTERNAL_CN_FLAGS \
(ISDOTDOT | MAKEENTRY | ISLASTCN)
@ -4197,6 +4197,7 @@ static bool
cache_fpl_istrailingslash(struct cache_fpl *fpl)
{
MPASS(fpl->nulchar > fpl->cnp->cn_pnbuf);
return (*(fpl->nulchar - 1) == '/');
}
@ -4767,6 +4768,54 @@ cache_fplookup_degenerate(struct cache_fpl *fpl)
return (cache_fpl_handled(fpl));
}
static int __noinline
cache_fplookup_emptypath(struct cache_fpl *fpl)
{
struct nameidata *ndp;
struct componentname *cnp;
enum vgetstate tvs;
struct vnode *tvp;
seqc_t tvp_seqc;
int error, lkflags;
fpl->tvp = fpl->dvp;
fpl->tvp_seqc = fpl->dvp_seqc;
ndp = fpl->ndp;
cnp = fpl->cnp;
tvp = fpl->tvp;
tvp_seqc = fpl->tvp_seqc;
MPASS(*cnp->cn_pnbuf == '\0');
MPASS((cnp->cn_flags & (LOCKPARENT | WANTPARENT)) == 0);
if (__predict_false((cnp->cn_flags & EMPTYPATH) == 0)) {
cache_fpl_smr_exit(fpl);
return (cache_fpl_handled_error(fpl, ENOENT));
}
tvs = vget_prep_smr(tvp);
cache_fpl_smr_exit(fpl);
if (__predict_false(tvs == VGET_NONE)) {
return (cache_fpl_aborted(fpl));
}
if ((cnp->cn_flags & LOCKLEAF) != 0) {
lkflags = LK_SHARED;
if ((cnp->cn_flags & LOCKSHARED) == 0)
lkflags = LK_EXCLUSIVE;
error = vget_finish(tvp, lkflags, tvs);
if (__predict_false(error != 0)) {
return (cache_fpl_aborted(fpl));
}
} else {
vget_finish_ref(tvp, tvs);
}
ndp->ni_resflags |= NIRES_EMPTYPATH;
return (cache_fpl_handled(fpl));
}
static int __noinline
cache_fplookup_noentry(struct cache_fpl *fpl)
{
@ -4799,6 +4848,10 @@ cache_fplookup_noentry(struct cache_fpl *fpl)
return (cache_fplookup_skip_slashes(fpl));
}
if (cnp->cn_pnbuf[0] == '\0') {
return (cache_fplookup_emptypath(fpl));
}
if (cnp->cn_nameptr[0] == '\0') {
if (fpl->tvp == NULL) {
return (cache_fplookup_degenerate(fpl));
@ -5486,6 +5539,7 @@ cache_fplookup_parse(struct cache_fpl *fpl)
*
* TODO: fix this to be word-sized.
*/
MPASS(&cnp->cn_nameptr[fpl->debug.ni_pathlen - 1] >= cnp->cn_pnbuf);
KASSERT(&cnp->cn_nameptr[fpl->debug.ni_pathlen - 1] == fpl->nulchar,
("%s: mismatch between pathlen (%zu) and nulchar (%p != %p), string [%s]\n",
__func__, fpl->debug.ni_pathlen, &cnp->cn_nameptr[fpl->debug.ni_pathlen - 1],
@ -5739,6 +5793,13 @@ cache_fplookup_failed_vexec(struct cache_fpl *fpl, int error)
dvp = fpl->dvp;
dvp_seqc = fpl->dvp_seqc;
/*
* Hack: delayed empty path checking.
*/
if (cnp->cn_pnbuf[0] == '\0') {
return (cache_fplookup_emptypath(fpl));
}
/*
* TODO: Due to ignoring trailing slashes lookup will perform a
* permission check on the last dir when it should not be doing it. It

18
sys/kern/vfs_lookup.c
View File

@ -463,13 +463,6 @@ namei_getpath(struct nameidata *ndp)
if (__predict_false(error != 0))
return (error);
/*
* Don't allow empty pathnames unless EMPTYPATH is specified.
* Caller checks for ENOENT as an indication for the empty path.
*/
if (__predict_false(*cnp->cn_pnbuf == '\0'))
return (ENOENT);
cnp->cn_nameptr = cnp->cn_pnbuf;
return (0);
}
@ -598,8 +591,6 @@ namei(struct nameidata *ndp)
error = namei_getpath(ndp);
if (__predict_false(error != 0)) {
if (error == ENOENT && (cnp->cn_flags & EMPTYPATH) != 0)
return (namei_emptypath(ndp));
namei_cleanup_cnp(cnp);
SDT_PROBE4(vfs, namei, lookup, return, error, NULL,
false, ndp);
@ -642,6 +633,15 @@ namei(struct nameidata *ndp)
case CACHE_FPL_STATUS_ABORTED:
TAILQ_INIT(&ndp->ni_cap_tracker);
MPASS(ndp->ni_lcf == 0);
if (*cnp->cn_pnbuf == '\0') {
if ((cnp->cn_flags & EMPTYPATH) != 0) {
return (namei_emptypath(ndp));
}
namei_cleanup_cnp(cnp);
SDT_PROBE4(vfs, namei, lookup, return, ENOENT, NULL,
false, ndp);
return (ENOENT);
}
error = namei_setup(ndp, &dp, &pwd);
if (error != 0) {
namei_cleanup_cnp(cnp);