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From: Mateusz Guzik <mjg@FreeBSD.org>
Date: Thu, 4 May 2017 03:11:59 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r317784 - head/sys/kern
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Author: mjg
Date: Thu May  4 03:11:59 2017
New Revision: 317784
URL: https://svnweb.freebsd.org/changeset/base/317784

Log:
  cache: stop holding the ncneg_hot lock across purging
  
  Only non-hot entries are purged so the lock is not needed in the first place.
  This saves one lock/unlock pair.
  
  MFC after:	1 week

Modified:
  head/sys/kern/vfs_cache.c

Modified: head/sys/kern/vfs_cache.c
==============================================================================
--- head/sys/kern/vfs_cache.c	Thu May  4 01:46:04 2017	(r317783)
+++ head/sys/kern/vfs_cache.c	Thu May  4 03:11:59 2017	(r317784)
@@ -735,13 +735,12 @@ cache_negative_remove(struct namecache *
 			list_locked = true;
 			mtx_lock(&neglist->nl_lock);
 		}
-	} else {
-		mtx_assert(&neglist->nl_lock, MA_OWNED);
-		mtx_assert(&ncneg_hot.nl_lock, MA_OWNED);
 	}
 	if (ncp->nc_flag & NCF_HOTNEGATIVE) {
+		mtx_assert(&ncneg_hot.nl_lock, MA_OWNED);
 		TAILQ_REMOVE(&ncneg_hot.nl_list, ncp, nc_dst);
 	} else {
+		mtx_assert(&neglist->nl_lock, MA_OWNED);
 		TAILQ_REMOVE(&neglist->nl_list, ncp, nc_dst);
 	}
 	if (list_locked)
@@ -816,7 +815,6 @@ cache_negative_zap_one(void)
 	mtx_unlock(&ncneg_hot.nl_lock);
 	mtx_lock(dvlp);
 	rw_wlock(blp);
-	mtx_lock(&ncneg_hot.nl_lock);
 	mtx_lock(&neglist->nl_lock);
 	ncp2 = TAILQ_FIRST(&neglist->nl_list);
 	if (ncp != ncp2 || dvlp != VP2VNODELOCK(ncp2->nc_dvp) ||
@@ -830,7 +828,6 @@ cache_negative_zap_one(void)
 	cache_zap_locked(ncp, true);
 out_unlock_all:
 	mtx_unlock(&neglist->nl_lock);
-	mtx_unlock(&ncneg_hot.nl_lock);
 	rw_wunlock(blp);
 	mtx_unlock(dvlp);
 out: