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To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org,
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From: Mateusz Guzik <mjg@FreeBSD.org>
Subject: git: 247f652e622d - stable/13 - cache: make ->nc_flag accesses
atomic-clean for lockless usage
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The branch stable/13 has been updated by mjg:
URL: https://cgit.FreeBSD.org/src/commit/?id=247f652e622d9aebda627ea34ba5af242dbb835e
commit 247f652e622d9aebda627ea34ba5af242dbb835e
Author: Mateusz Guzik <mjg@FreeBSD.org>
AuthorDate: 2021-01-25 20:58:59 +0000
Commit: Mateusz Guzik <mjg@FreeBSD.org>
CommitDate: 2021-02-01 12:39:17 +0000
cache: make ->nc_flag accesses atomic-clean for lockless usage
(cherry picked from commit 6ef8fede86f3feed7fb1e15b0e8a32ecfec33c6c)
---
sys/kern/vfs_cache.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)
diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c
index 9d5b18aa4132..ba3856ffe0b4 100644
--- a/sys/kern/vfs_cache.c
+++ b/sys/kern/vfs_cache.c
@@ -398,7 +398,7 @@ static inline struct negstate *
NCP2NEGSTATE(struct namecache *ncp)
{
- MPASS(ncp->nc_flag & NCF_NEGATIVE);
+ MPASS(atomic_load_char(&ncp->nc_flag) & NCF_NEGATIVE);
return (&ncp->nc_neg);
}
@@ -1994,7 +1994,7 @@ negative_success:
}
cache_out_ts(ncp, tsp, ticksp);
- whiteout = (ncp->nc_flag & NCF_WHITE);
+ whiteout = (atomic_load_char(&ncp->nc_flag) & NCF_WHITE);
neg_promote = cache_neg_hit_prep(ncp);
if (!cache_ncp_canuse(ncp)) {
cache_neg_hit_abort(ncp);
@@ -2149,6 +2149,7 @@ cache_enter_lock(struct celockstate *cel, struct vnode *dvp, struct vnode *vp,
{
struct namecache *ncp;
struct mtx *blps[2];
+ u_char nc_flag;
blps[0] = HASH2BUCKETLOCK(hash);
for (;;) {
@@ -2159,11 +2160,12 @@ cache_enter_lock(struct celockstate *cel, struct vnode *dvp, struct vnode *vp,
ncp = vp->v_cache_dd;
if (ncp == NULL)
break;
- if ((ncp->nc_flag & NCF_ISDOTDOT) == 0)
+ nc_flag = atomic_load_char(&ncp->nc_flag);
+ if ((nc_flag & NCF_ISDOTDOT) == 0)
break;
MPASS(ncp->nc_dvp == vp);
blps[1] = NCP2BUCKETLOCK(ncp);
- if (ncp->nc_flag & NCF_NEGATIVE)
+ if ((nc_flag & NCF_NEGATIVE) != 0)
break;
if (cache_lock_vnodes_cel_3(cel, ncp->nc_vp))
break;
@@ -2190,6 +2192,7 @@ cache_enter_lock_dd(struct celockstate *cel, struct vnode *dvp, struct vnode *vp
{
struct namecache *ncp;
struct mtx *blps[2];
+ u_char nc_flag;
blps[0] = HASH2BUCKETLOCK(hash);
for (;;) {
@@ -2198,11 +2201,12 @@ cache_enter_lock_dd(struct celockstate *cel, struct vnode *dvp, struct vnode *vp
ncp = dvp->v_cache_dd;
if (ncp == NULL)
break;
- if ((ncp->nc_flag & NCF_ISDOTDOT) == 0)
+ nc_flag = atomic_load_char(&ncp->nc_flag);
+ if ((nc_flag & NCF_ISDOTDOT) == 0)
break;
MPASS(ncp->nc_dvp == dvp);
blps[1] = NCP2BUCKETLOCK(ncp);
- if (ncp->nc_flag & NCF_NEGATIVE)
+ if ((nc_flag & NCF_NEGATIVE) != 0)
break;
if (cache_lock_vnodes_cel_3(cel, ncp->nc_vp))
break;
@@ -2436,7 +2440,7 @@ cache_enter_time(struct vnode *dvp, struct vnode *vp, struct componentname *cnp,
vp);
} else {
if (cnp->cn_flags & ISWHITEOUT)
- ncp->nc_flag |= NCF_WHITE;
+ atomic_store_char(&ncp->nc_flag, ncp->nc_flag | NCF_WHITE);
cache_neg_insert(ncp);
SDT_PROBE2(vfs, namecache, enter_negative, done, dvp,
ncp->nc_name);