From: Miklos Szeredi <mszeredi@redhat.com>
Date: Wed, 15 Aug 2018 17:42:34 +0200
Subject: fuse: delete dentry if timeout is zero
Git-commit: 8fab010644363f8f80194322aa7a81e38c867af3
Patch-mainline: v5.4-rc1
References: jsc#SLE-13782

Don't hold onto dentry in lru list if need to re-lookup it anyway at next
access.  Only do this if explicitly enabled, otherwise it could result in
performance regression.

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

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Acked-by: Luis Henriques <lhenriques@suse.com>
---
 fs/fuse/dir.c    | 28 +++++++++++++++++++++++++---
 fs/fuse/fuse_i.h |  3 +++
 2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 11334ee01dc9..ba0a175d7578 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -29,12 +29,28 @@ 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;
+	struct fuse_conn *fc = get_fuse_conn_super(dentry->d_sb);
+	bool delete = !time && fc->delete_stale;
+	/*
+	 * 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 ((!delete && (dentry->d_flags & DCACHE_OP_DELETE)) ||
+	    (delete && !(dentry->d_flags & DCACHE_OP_DELETE))) {
+		spin_lock(&dentry->d_lock);
+		if (!delete)
+			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 +271,14 @@ 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,
 };
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 242d47752e78..fed68a427a4c 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -692,6 +692,9 @@ struct fuse_conn {
 	/* Send DESTROY request */
 	unsigned int destroy:1;
 
+	/* Delete dentries that have gone stale */
+	unsigned int delete_stale:1;
+
 	/** The number of requests waiting for completion */
 	atomic_t num_waiting;