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cache: skip checking for spurious slashes if possible

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Tested by:	pho
This commit is contained in:
Mateusz Guzik 2021-01-01 05:05:04 +01:00
parent 33f3e81df5
commit 71a6a0b545
1 changed files with 67 additions and 2 deletions
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69
sys/kern/vfs_cache.c
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@ -3640,6 +3640,7 @@ struct cache_fpl {
static bool cache_fplookup_is_mp(struct cache_fpl *fpl);
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 void
cache_fpl_cleanup_cnp(struct componentname *cnp)
@ -4006,6 +4007,17 @@ cache_fplookup_partial_setup(struct cache_fpl *fpl)
if (cache_fpl_isdotdot(cnp))
cnp->cn_flags |= ISDOTDOT;
/*
* Skip potential extra slashes parsing did not take care of.
* cache_fplookup_skip_slashes explains the mechanism.
*/
if (__predict_false(*(cnp->cn_nameptr) == '/')) {
do {
cnp->cn_nameptr++;
ndp->ni_pathlen--;
} while (*(cnp->cn_nameptr) == '/');
}
return (0);
}
@ -4064,6 +4076,7 @@ cache_fplookup_final_modifying(struct cache_fpl *fpl)
dvp = fpl->dvp;
dvp_seqc = fpl->dvp_seqc;
MPASS(*(cnp->cn_nameptr) != '/');
MPASS(cache_fpl_islastcn(ndp));
if ((cnp->cn_flags & LOCKPARENT) == 0)
MPASS((cnp->cn_flags & WANTPARENT) != 0);
@ -4309,6 +4322,8 @@ cache_fplookup_final(struct cache_fpl *fpl)
dvp_seqc = fpl->dvp_seqc;
tvp = fpl->tvp;
MPASS(*(cnp->cn_nameptr) != '/');
if (cnp->cn_nameiop != LOOKUP) {
return (cache_fplookup_final_modifying(fpl));
}
@ -4397,6 +4412,7 @@ cache_fplookup_noentry(struct cache_fpl *fpl)
dvp = fpl->dvp;
dvp_seqc = fpl->dvp_seqc;
MPASS(*(cnp->cn_nameptr) != '/');
MPASS((cnp->cn_flags & MAKEENTRY) == 0);
MPASS((cnp->cn_flags & ISDOTDOT) == 0);
MPASS(!cache_fpl_isdotdot(cnp));
@ -4664,6 +4680,9 @@ cache_fplookup_next(struct cache_fpl *fpl)
}
if (__predict_false(ncp == NULL)) {
if (cnp->cn_nameptr[0] == '/') {
return (cache_fplookup_skip_slashes(fpl));
}
return (cache_fplookup_noentry(fpl));
}
@ -4969,10 +4988,56 @@ cache_fplookup_parse_advance(struct cache_fpl *fpl)
cnp = fpl->cnp;
cnp->cn_nameptr = ndp->ni_next;
while (*cnp->cn_nameptr == '/') {
KASSERT(*(cnp->cn_nameptr) == '/',
("%s: should have seen slash at %p ; buf %p [%s]\n", __func__,
cnp->cn_nameptr, cnp->cn_pnbuf, cnp->cn_pnbuf));
cnp->cn_nameptr++;
ndp->ni_pathlen--;
}
/*
* Skip spurious slashes in a pathname (e.g., "foo///bar") and retry.
*
* Lockless lookup tries to elide checking for spurious slashes and should they
* be present is guaranteed to fail to find an entry. In this case the caller
* must check if the name starts with a slash and this call routine. It is
* going to fast forward across the spurious slashes and set the state up for
* retry.
*/
static int __noinline
cache_fplookup_skip_slashes(struct cache_fpl *fpl)
{
struct nameidata *ndp;
struct componentname *cnp;
ndp = fpl->ndp;
cnp = fpl->cnp;
MPASS(*(cnp->cn_nameptr) == '/');
do {
cnp->cn_nameptr++;
ndp->ni_pathlen--;
}
} while (*(cnp->cn_nameptr) == '/');
/*
* Go back to one slash so that cache_fplookup_parse_advance has
* something to skip.
*/
cnp->cn_nameptr--;
ndp->ni_pathlen++;
/*
* cache_fplookup_parse_advance starts from ndp->ni_next
*/
ndp->ni_next = cnp->cn_nameptr;
/*
* Retry the lookup, similar to dot lookups.
*/
fpl->tvp = fpl->dvp;
fpl->tvp_seqc = fpl->dvp_seqc;
return (0);
}
/*