linux-kernel - [PATCH RFC 7/8] dcache: push releasing dentry lock into sweep

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Message-ID: <158894061026.200862.15846101347037556126.stgit@buzz>
Date:   Fri, 08 May 2020 15:23:30 +0300
From:   Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, Alexander Viro <viro@...iv.linux.org.uk>
Cc:     Waiman Long <longman@...hat.com>
Subject: [PATCH RFC 7/8] dcache: push releasing dentry lock into
 sweep_negative

This is preparation for the next patch.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
---
 fs/dcache.c |   12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 0fd2e02e507b..60158065891e 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -636,15 +636,17 @@ static inline struct dentry *lock_parent(struct dentry *dentry)
  * Move cached negative dentry to the tail of parent->d_subdirs.
  * This lets walkers skip them all together at first sight.
  * Must be called at dput of negative dentry.
+ * dentry->d_lock must be held, returns with it unlocked.
  */
 static void sweep_negative(struct dentry *dentry)
+	__releases(dentry->d_lock)
 {
 	struct dentry *parent;
 
 	if (!d_is_tail_negative(dentry)) {
 		parent = lock_parent(dentry);
 		if (!parent)
-			return;
+			goto out;
 
 		if (!d_count(dentry) && d_is_negative(dentry) &&
 		    !d_is_tail_negative(dentry)) {
@@ -654,6 +656,8 @@ static void sweep_negative(struct dentry *dentry)
 
 		spin_unlock(&parent->d_lock);
 	}
+out:
+	spin_unlock(&dentry->d_lock);
 }
 
 /*
@@ -747,7 +751,8 @@ static struct dentry *dentry_kill(struct dentry *dentry)
 		spin_unlock(&parent->d_lock);
 	if (d_is_negative(dentry))
 		sweep_negative(dentry);
-	spin_unlock(&dentry->d_lock);
+	else
+		spin_unlock(&dentry->d_lock);
 	return NULL;
 }
 
@@ -905,7 +910,8 @@ void dput(struct dentry *dentry)
 		if (likely(retain_dentry(dentry))) {
 			if (d_is_negative(dentry))
 				sweep_negative(dentry);
-			spin_unlock(&dentry->d_lock);
+			else
+				spin_unlock(&dentry->d_lock);
 			return;
 		}