svn commit: r366742 - head/sys/kern

[Mateusz Guzik]

Author: mjg
Date: Fri Oct 16 00:55:57 2020
New Revision: 366742
URL: https://svnweb.freebsd.org/changeset/base/366742

Log:
  cache: elide vhold/vdrop around promoting negative entry

Modified:
  head/sys/kern/vfs_cache.c

Modified: head/sys/kern/vfs_cache.c
==============================================================================
--- head/sys/kern/vfs_cache.c	Fri Oct 16 00:55:31 2020	(r366741)
+++ head/sys/kern/vfs_cache.c	Fri Oct 16 00:55:57 2020	(r366742)
@@ -3394,9 +3394,6 @@ cache_fplookup_negative_promote(struct cache_fpl *fpl,
 	cnp = fpl->cnp;
 	dvp = fpl->dvp;
 
-	if (!vhold_smr(dvp))
-		return (cache_fpl_aborted(fpl));
-
 	nl = NCP2NEGLIST(oncp);
 	cache_fpl_smr_exit(fpl);
 
@@ -3409,6 +3406,10 @@ cache_fplookup_negative_promote(struct cache_fpl *fpl,
 	/*
 	 * Avoid all surprises by only succeeding if we got the same entry and
 	 * bailing completely otherwise.
+	 * XXX There are no provisions to keep the vnode around, meaning we may
+	 * end up promoting a negative entry for a *new* vnode and returning
+	 * ENOENT on its account. This is the error we want to return anyway
+	 * and promotion is harmless.
 	 *
 	 * In particular at this point there can be a new ncp which matches the
 	 * search but hashes to a different neglist.
@@ -3451,12 +3452,10 @@ cache_fplookup_negative_promote(struct cache_fpl *fpl,
 	counter_u64_add(numneghits, 1);
 	cache_fpl_smr_exit(fpl);
 	mtx_unlock(&nl->nl_lock);
-	vdrop(dvp);
 	return (cache_fpl_handled(fpl, ENOENT));
 out_abort:
 	cache_fpl_smr_exit(fpl);
 	mtx_unlock(&nl->nl_lock);
-	vdrop(dvp);
 	return (cache_fpl_aborted(fpl));
 }