Continue on-going campaign to replace lockmgr locks with sx locks where

the specific semantics of ockmgr aren't required: update UFS1 extended
attributes to protect its data structures using an sx lock.

While here, update comments on lock granularity.

MFC after:	2 weeks

2 files changed, 14 insertions, 12 deletions

diff --git a/sys/ufs/ufs/extattr.h b/sys/ufs/ufs/extattr.h
index c1ceee5..5d26bf6 100644
--- a/sys/ufs/ufs/extattr.h
+++ b/sys/ufs/ufs/extattr.h
@@ -113,6 +113,8 @@ struct extattr {
 
 #ifdef _KERNEL
 
+#include <sys/_sx.h>
+
 #ifdef MALLOC_DECLARE
 MALLOC_DECLARE(M_EXTATTR);
 #endif
@@ -127,10 +129,9 @@ struct ufs_extattr_list_entry {
 	struct vnode	*uele_backing_vnode;
 };
 
-struct lock;
 struct ucred;
 struct ufs_extattr_per_mount {
-	struct lock	uepm_lock;
+	struct sx	uepm_lock;
 	struct ufs_extattr_list_head	uepm_list;
 	struct ucred	*uepm_ucred;
 	int	uepm_flags;
diff --git a/sys/ufs/ufs/ufs_extattr.c b/sys/ufs/ufs/ufs_extattr.c
index 0c50351..dcfd7d9 100644
--- a/sys/ufs/ufs/ufs_extattr.c
+++ b/sys/ufs/ufs/ufs_extattr.c
@@ -55,6 +55,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/lock.h>
 #include <sys/dirent.h>
 #include <sys/extattr.h>
+#include <sys/sx.h>
 #include <sys/sysctl.h>
 
 #include <vm/uma.h>
@@ -95,23 +96,23 @@ static int	ufs_extattr_rm(struct vnode *vp, int attrnamespace,
 
 /*
  * Per-FS attribute lock protecting attribute operations.
- * XXX Right now there is a lot of lock contention due to having a single
- * lock per-FS; really, this should be far more fine-grained.
+ *
+ * XXXRW: Perhaps something more fine-grained would be appropriate, but at
+ * the end of the day we're going to contend on the vnode lock for the
+ * backing file anyway.
  */
 static void
 ufs_extattr_uepm_lock(struct ufsmount *ump, struct thread *td)
 {
 
-	/* Ideally, LK_CANRECURSE would not be used, here. */
-	lockmgr(&ump->um_extattr.uepm_lock, LK_EXCLUSIVE | LK_RETRY |
-	    LK_CANRECURSE, 0);
+	sx_xlock(&ump->um_extattr.uepm_lock);
 }
 
 static void
 ufs_extattr_uepm_unlock(struct ufsmount *ump, struct thread *td)
 {
 
-	lockmgr(&ump->um_extattr.uepm_lock, LK_RELEASE, 0);
+	sx_xunlock(&ump->um_extattr.uepm_lock);
 }
 
 /*-
@@ -143,6 +144,8 @@ ufs_extattr_find_attr(struct ufsmount *ump, int attrnamespace,
 {
 	struct ufs_extattr_list_entry *search_attribute;
 
+	sx_assert(&ump->um_extattr.uepm_lock, SA_XLOCKED);
+
 	for (search_attribute = LIST_FIRST(&ump->um_extattr.uepm_list);
 	    search_attribute != NULL;
 	    search_attribute = LIST_NEXT(search_attribute, uele_entries)) {
@@ -165,10 +168,8 @@ ufs_extattr_uepm_init(struct ufs_extattr_per_mount *uepm)
 {
 
 	uepm->uepm_flags = 0;
-
 	LIST_INIT(&uepm->uepm_list);
-	/* XXX is PVFS right, here? */
-	lockinit(&uepm->uepm_lock, PVFS, "extattr", 0, 0);
+	sx_init(&uepm->uepm_lock, "ufs_extattr_sx");
 	uepm->uepm_flags |= UFS_EXTATTR_UEPM_INITIALIZED;
 }
 
@@ -192,7 +193,7 @@ ufs_extattr_uepm_destroy(struct ufs_extattr_per_mount *uepm)
 	 * during unmount, and with vfs_busy().
 	 */
 	uepm->uepm_flags &= ~UFS_EXTATTR_UEPM_INITIALIZED;
-	lockdestroy(&uepm->uepm_lock);
+	sx_destroy(&uepm->uepm_lock);
 }
 
 /*