Author: mjg
Date: Thu Jul 2 12:54:50 2020
New Revision: 362888
URL: https://svnweb.freebsd.org/changeset/base/362888
Log:
cache: fix misplaced fence in cache_ncp_invalidate
The intent was to mark the entry as invalid before cache_zap starts messing
with it.
While here add some comments.
Modified:
head/sys/kern/vfs_cache.c
Modified: head/sys/kern/vfs_cache.c
==============================================================================
--- head/sys/kern/vfs_cache.c Thu Jul 2 10:44:45 2020 (r362887)
+++ head/sys/kern/vfs_cache.c Thu Jul 2 12:54:50 2020 (r362888)
@@ -147,22 +147,33 @@ struct namecache_ts {
#define NCF_HOTNEGATIVE 0x40
#define NCF_INVALID 0x80
-static bool
-cache_ncp_invalid(struct namecache *ncp)
-{
-
- atomic_thread_fence_acq();
- return ((ncp->nc_flag & NCF_INVALID) != 0);
-}
-
+/*
+ * Mark an entry as invalid.
+ *
+ * This is called before it starts getting deconstructed.
+ */
static void
cache_ncp_invalidate(struct namecache *ncp)
{
- atomic_thread_fence_rel();
KASSERT((ncp->nc_flag & NCF_INVALID) == 0,
("%s: entry %p already invalid", __func__, ncp));
ncp->nc_flag |= NCF_INVALID;
+ atomic_thread_fence_rel();
+}
+
+/*
+ * Verify validity of an entry.
+ *
+ * All places which elide locks are supposed to call this after they are
+ * done with reading from an entry.
+ */
+static bool
+cache_ncp_invalid(struct namecache *ncp)
+{
+
+ atomic_thread_fence_acq();
+ return ((ncp->nc_flag & NCF_INVALID) != 0);
}
/*
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