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cache: add delayed degenerate path handling

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This commit is contained in:
Mateusz Guzik 2021-01-31 21:54:35 +01:00
parent bbfb1edd70
commit 6f19dc2124
1 changed files with 25 additions and 32 deletions
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57
sys/kern/vfs_cache.c
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@ -3737,7 +3737,6 @@ static int cache_fplookup_cross_mount(struct cache_fpl *fpl);
static int cache_fplookup_partial_setup(struct cache_fpl *fpl);
static int cache_fplookup_skip_slashes(struct cache_fpl *fpl);
static int cache_fplookup_trailingslash(struct cache_fpl *fpl);
static int cache_fplookup_preparse(struct cache_fpl *fpl);
static void cache_fpl_pathlen_dec(struct cache_fpl *fpl);
static void cache_fpl_pathlen_inc(struct cache_fpl *fpl);
static void cache_fpl_pathlen_add(struct cache_fpl *fpl, size_t n);
@ -4518,6 +4517,9 @@ cache_fplookup_degenerate(struct cache_fpl *fpl)
struct vnode *dvp;
enum vgetstate dvs;
int error, lkflags;
#ifdef INVARIANTS
char *cp;
#endif
fpl->tvp = fpl->dvp;
fpl->tvp_seqc = fpl->dvp_seqc;
@ -4525,6 +4527,14 @@ cache_fplookup_degenerate(struct cache_fpl *fpl)
cnp = fpl->cnp;
dvp = fpl->dvp;
#ifdef INVARIANTS
for (cp = cnp->cn_pnbuf; *cp != '\0'; cp++) {
KASSERT(*cp == '/',
("%s: encountered non-slash; string [%s]\n", __func__,
cnp->cn_pnbuf));
}
#endif
if (__predict_false(cnp->cn_nameiop != LOOKUP)) {
cache_fpl_smr_exit(fpl);
return (cache_fpl_handled_error(fpl, EISDIR));
@ -4589,6 +4599,9 @@ cache_fplookup_noentry(struct cache_fpl *fpl)
}
if (cnp->cn_nameptr[0] == '\0') {
if (fpl->tvp == NULL) {
return (cache_fplookup_degenerate(fpl));
}
return (cache_fplookup_trailingslash(fpl));
}
@ -4897,7 +4910,7 @@ cache_symlink_resolve(struct cache_fpl *fpl, const char *string, size_t len)
cache_fpl_pathlen_add(fpl, adjust);
cnp->cn_nameptr = cnp->cn_pnbuf;
fpl->nulchar = &cnp->cn_nameptr[ndp->ni_pathlen - 1];
fpl->tvp = NULL;
return (0);
}
@ -4957,8 +4970,7 @@ cache_fplookup_symlink(struct cache_fpl *fpl)
return (cache_fpl_aborted(fpl));
}
}
return (cache_fplookup_preparse(fpl));
return (0);
}
static int
@ -5238,30 +5250,6 @@ cache_fpl_pathlen_dec(struct cache_fpl *fpl)
}
#endif
static int __always_inline
cache_fplookup_preparse(struct cache_fpl *fpl)
{
struct componentname *cnp;
cnp = fpl->cnp;
if (__predict_false(cnp->cn_nameptr[0] == '\0')) {
return (cache_fplookup_degenerate(fpl));
}
/*
* By this point the shortest possible pathname is one character + nul
* terminator, hence 2.
*/
KASSERT(fpl->debug.ni_pathlen >= 2, ("%s: pathlen %zu\n", __func__,
fpl->debug.ni_pathlen));
KASSERT(&cnp->cn_nameptr[fpl->debug.ni_pathlen - 2] == fpl->nulchar - 1,
("%s: mismatch on string (%p != %p) [%s]\n", __func__,
&cnp->cn_nameptr[fpl->debug.ni_pathlen - 2], fpl->nulchar - 1,
cnp->cn_pnbuf));
return (0);
}
static void
cache_fplookup_parse(struct cache_fpl *fpl)
{
@ -5533,6 +5521,13 @@ cache_fplookup_failed_vexec(struct cache_fpl *fpl, int error)
dvp = fpl->dvp;
dvp_seqc = fpl->dvp_seqc;
/*
* Hack: delayed degenerate path checking.
*/
if (cnp->cn_nameptr[0] == '\0' && fpl->tvp == NULL) {
return (cache_fplookup_degenerate(fpl));
}
/*
* Hack: delayed name len checking.
*/
@ -5624,10 +5619,7 @@ cache_fplookup_impl(struct vnode *dvp, struct cache_fpl *fpl)
return (cache_fpl_aborted(fpl));
}
error = cache_fplookup_preparse(fpl);
if (__predict_false(cache_fpl_terminated(fpl))) {
return (error);
}
MPASS(fpl->tvp == NULL);
for (;;) {
cache_fplookup_parse(fpl);
@ -5787,6 +5779,7 @@ cache_fplookup(struct nameidata *ndp, enum cache_fpl_status *status,
fpl.nulchar = &cnp->cn_nameptr[ndp->ni_pathlen - 1];
fpl.fsearch = false;
fpl.savename = (cnp->cn_flags & SAVENAME) != 0;
fpl.tvp = NULL; /* for degenerate path handling */
fpl.pwd = pwdp;
pwd = pwd_get_smr();
*(fpl.pwd) = pwd;