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Date:   Wed, 21 Aug 2019 17:09:31 -0700
Message-Id: <20190822000933.180870-1-khazhy@google.com>
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Subject: [PATCH 1/3] fuse: on 64-bit store time in d_fsdata directly
From:   Khazhismel Kumykov <khazhy@google.com>
To:     miklos@szeredi.hu
Cc:     linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        shakeelb@google.com, Khazhismel Kumykov <khazhy@google.com>
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Sender: linux-kernel-owner@vger.kernel.org
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Implements the optimization noted in f75fdf22b0a8 ("fuse: don't use
->d_time"), as the additional memory can be significant. (In particular,
on SLAB configurations this 8-byte alloc becomes 32 bytes). Per-dentry,
this can consume significant memory.

Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
---
 fs/fuse/dir.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index dd0f64f7bc06..f9c59a296568 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -24,6 +24,18 @@ static void fuse_advise_use_readdirplus(struct inode *dir)
 	set_bit(FUSE_I_ADVISE_RDPLUS, &fi->state);
 }
 
+#if BITS_PER_LONG >= 64
+static inline void fuse_dentry_settime(struct dentry *entry, u64 time)
+{
+	entry->d_fsdata = (void *) time;
+}
+
+static inline u64 fuse_dentry_time(struct dentry *entry)
+{
+	return (u64)entry->d_fsdata;
+}
+
+#else
 union fuse_dentry {
 	u64 time;
 	struct rcu_head rcu;
@@ -38,6 +50,7 @@ static inline u64 fuse_dentry_time(struct dentry *entry)
 {
 	return ((union fuse_dentry *) entry->d_fsdata)->time;
 }
+#endif
 
 /*
  * FUSE caches dentries and attributes with separate timeout.  The
@@ -242,6 +255,7 @@ static int fuse_dentry_revalidate(struct dentry *entry, unsigned int flags)
 	goto out;
 }
 
+#if BITS_PER_LONG < 64
 static int fuse_dentry_init(struct dentry *dentry)
 {
 	dentry->d_fsdata = kzalloc(sizeof(union fuse_dentry), GFP_KERNEL);
@@ -254,16 +268,21 @@ static void fuse_dentry_release(struct dentry *dentry)
 
 	kfree_rcu(fd, rcu);
 }
+#endif
 
 const struct dentry_operations fuse_dentry_operations = {
 	.d_revalidate	= fuse_dentry_revalidate,
+#if BITS_PER_LONG < 64
 	.d_init		= fuse_dentry_init,
 	.d_release	= fuse_dentry_release,
+#endif
 };
 
 const struct dentry_operations fuse_root_dentry_operations = {
+#if BITS_PER_LONG < 64
 	.d_init		= fuse_dentry_init,
 	.d_release	= fuse_dentry_release,
+#endif
 };
 
 int fuse_valid_type(int m)
-- 
2.23.0.187.g17f5b7556c-goog