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vfs: partially support file create/delete/rename in lockless lookup

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Perform the lookup until the last 2 elements and fallback to slowpath.

Tested by:	pho
Sponsored by:	The FreeBSD Foundation
This commit is contained in:
Mateusz Guzik 2020-08-10 10:35:18 +00:00
parent 21d5af2b30
commit 3ba0e51703
1 changed files with 28 additions and 6 deletions
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34
sys/kern/vfs_cache.c
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@ -3143,8 +3143,8 @@ cache_fpl_handled_impl(struct cache_fpl *fpl, int error, int line)
#define cache_fpl_handled(x, e) cache_fpl_handled_impl((x), (e), __LINE__)
#define CACHE_FPL_SUPPORTED_CN_FLAGS \
(LOCKLEAF | LOCKPARENT | WANTPARENT | FOLLOW | LOCKSHARED | SAVENAME | \
ISOPEN | NOMACCHECK | AUDITVNODE1 | AUDITVNODE2)
(LOCKLEAF | LOCKPARENT | WANTPARENT | NOCACHE | FOLLOW | LOCKSHARED | SAVENAME | \
WILLBEDIR | ISOPEN | NOMACCHECK | AUDITVNODE1 | AUDITVNODE2)
#define CACHE_FPL_INTERNAL_CN_FLAGS \
(ISDOTDOT | MAKEENTRY | ISLASTCN)
@ -3194,10 +3194,6 @@ cache_can_fplookup(struct cache_fpl *fpl)
cache_fpl_aborted(fpl);
return (false);
}
if (cnp->cn_nameiop != LOOKUP) {
cache_fpl_aborted(fpl);
return (false);
}
if (ndp->ni_dirfd != AT_FDCWD) {
cache_fpl_aborted(fpl);
return (false);
@ -3407,6 +3403,22 @@ cache_fplookup_final_child(struct cache_fpl *fpl, enum vgetstate tvs)
return (cache_fpl_handled(fpl, 0));
}
/*
* They want to possibly modify the state of the namecache.
*
* Don't try to match the API contract, just leave.
* TODO: this leaves scalability on the table
*/
static int
cache_fplookup_final_modifying(struct cache_fpl *fpl)
{
struct componentname *cnp;
cnp = fpl->cnp;
MPASS(cnp->cn_nameiop != LOOKUP);
return (cache_fpl_partial(fpl));
}
static int __noinline
cache_fplookup_final_withparent(struct cache_fpl *fpl)
{
@ -3489,6 +3501,10 @@ cache_fplookup_final(struct cache_fpl *fpl)
VNPASS(cache_fplookup_vnode_supported(dvp), dvp);
if (cnp->cn_nameiop != LOOKUP) {
return (cache_fplookup_final_modifying(fpl));
}
if ((cnp->cn_flags & (LOCKPARENT|WANTPARENT)) != 0)
return (cache_fplookup_final_withparent(fpl));
@ -3633,6 +3649,12 @@ cache_fplookup_next(struct cache_fpl *fpl)
tvp = atomic_load_ptr(&ncp->nc_vp);
nc_flag = atomic_load_char(&ncp->nc_flag);
if ((nc_flag & NCF_NEGATIVE) != 0) {
/*
* If they want to create an entry we need to replace this one.
*/
if (__predict_false(fpl->cnp->cn_nameiop == CREATE)) {
return (cache_fpl_partial(fpl));
}
negstate = NCP2NEGSTATE(ncp);
neg_hot = ((negstate->neg_flag & NEG_HOT) != 0);
if (__predict_false(!cache_ncp_canuse(ncp))) {