git: 1365b5f86f63 - main - cache: fold NCF_WHITE check into the rest

[Mateusz Guzik]

The branch main has been updated by mjg:

URL: https://cgit.FreeBSD.org/src/commit/?id=1365b5f86f631ab6b30fd5f71685e39aa8887474

commit 1365b5f86f631ab6b30fd5f71685e39aa8887474
Author:     Mateusz Guzik <mjg at FreeBSD.org>
AuthorDate: 2020-12-28 11:24:48 +0000
Commit:     Mateusz Guzik <mjg at FreeBSD.org>
CommitDate: 2021-01-01 00:10:43 +0000

    cache: fold NCF_WHITE check into the rest
    
    Tested by:      pho
---
 sys/kern/vfs_cache.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c
index 40cd174e1022..4b8940b7511c 100644
--- a/sys/kern/vfs_cache.c
+++ b/sys/kern/vfs_cache.c
@@ -263,6 +263,18 @@ cache_ncp_invalidate(struct namecache *ncp)
 	__predict_true((_nc_flag & (NCF_INVALID | NCF_WIP)) == 0);	\
 })
 
+/*
+ * Like the above but also checks NCF_WHITE.
+ */
+#define cache_fpl_neg_ncp_canuse(ncp)	({				\
+	struct namecache *_ncp = (ncp);					\
+	u_char _nc_flag;						\
+									\
+	atomic_thread_fence_acq();					\
+	_nc_flag = atomic_load_char(&_ncp->nc_flag);			\
+	__predict_true((_nc_flag & (NCF_INVALID | NCF_WIP | NCF_WHITE)) == 0);	\
+})
+
 /*
  * Name caching works as follows:
  *
@@ -4505,11 +4517,7 @@ cache_fplookup_neg(struct cache_fpl *fpl, struct namecache *ncp, uint32_t hash)
 		return (cache_fplookup_modifying(fpl));
 	}
 	neg_promote = cache_neg_hit_prep(ncp);
-	if (!cache_ncp_canuse(ncp)) {
-		cache_neg_hit_abort(ncp);
-		return (cache_fpl_partial(fpl));
-	}
-	if (__predict_false((nc_flag & NCF_WHITE) != 0)) {
+	if (!cache_fpl_neg_ncp_canuse(ncp)) {
 		cache_neg_hit_abort(ncp);
 		return (cache_fpl_partial(fpl));
 	}