[Devel] [PATCH RHEL7 COMMIT] ms/dcache: split dentry_kill()

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-327.18.2.vz7.14.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-327.18.2.vz7.14.8
------>
commit 6376a8e3aca123ad0eb84ff2e306ce93404e4dad
Author: Al Viro <viro at zeniv.linux.org.uk>
Date:   Fri May 27 12:53:11 2016 +0400

    ms/dcache: split dentry_kill()
    
    ... into trylocks and everything else.  The latter (actual killing)
    is __dentry_kill().
    
    Signed-off-by: Al Viro <viro at zeniv.linux.org.uk>
    (cherry picked from commit e55fd011549eae01a230e3cace6f4d031b6a3453)
    Signed-off-by: Vladimir Davydov <vdavydov at virtuozzo.com>
    
    Conflicts:
    	fs/dcache.c
---
 fs/dcache.c | 66 +++++++++++++++++++++++++++++++++++--------------------------
 1 file changed, 38 insertions(+), 28 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 37420f4..70b34bd 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -482,37 +482,12 @@ void d_drop(struct dentry *dentry)
 }
 EXPORT_SYMBOL(d_drop);
 
-/*
- * Finish off a dentry we've decided to kill.
- * dentry->d_lock must be held, returns with it unlocked.
- * If ref is non-zero, then decrement the refcount too.
- * Returns dentry requiring refcount drop, or NULL if we're done.
- */
-static inline struct dentry *
-dentry_kill(struct dentry *dentry, int unlock_on_failure)
-	__releases(dentry->d_lock)
+static void __dentry_kill(struct dentry *dentry)
 {
-	struct inode *inode;
-	struct dentry *parent;
+	struct dentry *parent = NULL;
 
-	inode = dentry->d_inode;
-	if (inode && !spin_trylock(&inode->i_lock)) {
-relock:
-		if (unlock_on_failure) {
-			spin_unlock(&dentry->d_lock);
-			cpu_relax();
-		}
-		return dentry; /* try again with same dentry */
-	}
-	if (IS_ROOT(dentry))
-		parent = NULL;
-	else
+	if (!IS_ROOT(dentry))
 		parent = dentry->d_parent;
-	if (parent && !spin_trylock(&parent->d_lock)) {
-		if (inode)
-			spin_unlock(&inode->i_lock);
-		goto relock;
-	}
 
 	/*
 	 * The dentry is now unrecoverably dead to the world.
@@ -546,7 +521,42 @@ relock:
 	 * transient RCU lookups) can reach this dentry.
 	 */
 	d_free(dentry);
+}
+
+/*
+ * Finish off a dentry we've decided to kill.
+ * dentry->d_lock must be held, returns with it unlocked.
+ * If ref is non-zero, then decrement the refcount too.
+ * Returns dentry requiring refcount drop, or NULL if we're done.
+ */
+static struct dentry *
+dentry_kill(struct dentry *dentry, int unlock_on_failure)
+	__releases(dentry->d_lock)
+{
+	struct inode *inode = dentry->d_inode;
+	struct dentry *parent = NULL;
+
+	if (inode && unlikely(!spin_trylock(&inode->i_lock)))
+		goto failed;
+
+	if (!IS_ROOT(dentry)) {
+		parent = dentry->d_parent;
+		if (unlikely(!spin_trylock(&parent->d_lock))) {
+			if (inode)
+				spin_unlock(&inode->i_lock);
+			goto failed;
+		}
+	}
+
+	__dentry_kill(dentry);
 	return parent;
+
+failed:
+	if (unlock_on_failure) {
+		spin_unlock(&dentry->d_lock);
+		cpu_relax();
+	}
+	return dentry; /* try again with same dentry */
 }
 
 /*