linux-kernel - [PATCH v2 01/30] fuse: delete dentry if timeout is zero

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Message-Id: <20190515192715.18000-2-vgoyal@redhat.com>
Date:   Wed, 15 May 2019 15:26:46 -0400
From:   Vivek Goyal <vgoyal@...hat.com>
To:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, linux-nvdimm@...ts.01.org
Cc:     vgoyal@...hat.com, miklos@...redi.hu, stefanha@...hat.com,
        dgilbert@...hat.com, swhiteho@...hat.com
Subject: [PATCH v2 01/30] fuse: delete dentry if timeout is zero

From: Miklos Szeredi <mszeredi@...hat.com>

Don't hold onto dentry in lru list if need to re-lookup it anyway at next
access.

More advanced version of this patch would periodically flush out dentries
from the lru which have gone stale.

Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
---
 fs/fuse/dir.c | 26 +++++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index dd0f64f7bc06..fd8636e67ae9 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -29,12 +29,26 @@ union fuse_dentry {
 	struct rcu_head rcu;
 };
 
-static inline void fuse_dentry_settime(struct dentry *entry, u64 time)
+static void fuse_dentry_settime(struct dentry *dentry, u64 time)
 {
-	((union fuse_dentry *) entry->d_fsdata)->time = time;
+	/*
+	 * Mess with DCACHE_OP_DELETE because dput() will be faster without it.
+	 *  Don't care about races, either way it's just an optimization
+	 */
+	if ((time && (dentry->d_flags & DCACHE_OP_DELETE)) ||
+	    (!time && !(dentry->d_flags & DCACHE_OP_DELETE))) {
+		spin_lock(&dentry->d_lock);
+		if (time)
+			dentry->d_flags &= ~DCACHE_OP_DELETE;
+		else
+			dentry->d_flags |= DCACHE_OP_DELETE;
+		spin_unlock(&dentry->d_lock);
+	}
+
+	((union fuse_dentry *) dentry->d_fsdata)->time = time;
 }
 
-static inline u64 fuse_dentry_time(struct dentry *entry)
+static inline u64 fuse_dentry_time(const struct dentry *entry)
 {
 	return ((union fuse_dentry *) entry->d_fsdata)->time;
 }
@@ -255,8 +269,14 @@ static void fuse_dentry_release(struct dentry *dentry)
 	kfree_rcu(fd, rcu);
 }
 
+static int fuse_dentry_delete(const struct dentry *dentry)
+{
+	return time_before64(fuse_dentry_time(dentry), get_jiffies_64());
+}
+
 const struct dentry_operations fuse_dentry_operations = {
 	.d_revalidate	= fuse_dentry_revalidate,
+	.d_delete	= fuse_dentry_delete,
 	.d_init		= fuse_dentry_init,
 	.d_release	= fuse_dentry_release,
 };
-- 
2.20.1