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cache: support lockless lookup of degenerate paths

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Tested by:	pho
This commit is contained in:
Mateusz Guzik 2020-12-28 07:53:17 +01:00 committed by Mateusz Guzik
parent 1d6eb97677
commit 0b5bd1afd8
1 changed files with 52 additions and 9 deletions
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61
sys/kern/vfs_cache.c
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@ -4224,6 +4224,56 @@ cache_fplookup_final(struct cache_fpl *fpl)
return (cache_fplookup_final_child(fpl, tvs));
}
/*
* Comment from locked lookup:
* Check for degenerate name (e.g. / or "") which is a way of talking about a
* directory, e.g. like "/." or ".".
*/
static int __noinline
cache_fplookup_degenerate(struct cache_fpl *fpl)
{
struct componentname *cnp;
struct vnode *dvp;
enum vgetstate dvs;
int error, lkflags;
fpl->tvp = fpl->dvp;
fpl->tvp_seqc = fpl->dvp_seqc;
cnp = fpl->cnp;
dvp = fpl->dvp;
if (__predict_false(cnp->cn_nameiop != LOOKUP)) {
cache_fpl_smr_exit(fpl);
return (cache_fpl_handled(fpl, EISDIR));
}
MPASS((cnp->cn_flags & SAVESTART) == 0);
if ((cnp->cn_flags & (LOCKPARENT|WANTPARENT)) != 0) {
return (cache_fplookup_final_withparent(fpl));
}
dvs = vget_prep_smr(dvp);
cache_fpl_smr_exit(fpl);
if (__predict_false(dvs == 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(dvp, lkflags, dvs);
if (__predict_false(error != 0)) {
return (cache_fpl_aborted(fpl));
}
} else {
vget_finish_ref(dvp, dvs);
}
return (cache_fpl_handled(fpl, 0));
}
static int __noinline
cache_fplookup_noentry(struct cache_fpl *fpl)
{
@ -4694,15 +4744,8 @@ cache_fplookup_preparse(struct cache_fpl *fpl)
ndp = fpl->ndp;
cnp = fpl->cnp;
/*
* TODO
* Original comment:
* Check for degenerate name (e.g. / or "")
* which is a way of talking about a directory,
* e.g. like "/." or ".".
*/
if (__predict_false(cnp->cn_nameptr[0] == '\0')) {
return (cache_fpl_aborted(fpl));
return (cache_fplookup_degenerate(fpl));
}
/*
@ -4913,7 +4956,7 @@ cache_fplookup_impl(struct vnode *dvp, struct cache_fpl *fpl)
VNPASS(cache_fplookup_vnode_supported(fpl->dvp), fpl->dvp);
error = cache_fplookup_preparse(fpl);
if (__predict_false(error != 0)) {
if (__predict_false(cache_fpl_terminated(fpl))) {
goto out;
}