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[PATCH 6/8] nfs: don't use ->d_time

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  [PATCH 6/8] nfs: don't use ->d_time Miklos Szeredi <mszeredi@redhat.com> - 2016-06-22 16:40 +0200
    Re: [PATCH 6/8] nfs: don't use ->d_time Al Viro <viro@ZenIV.linux.org.uk> - 2016-06-22 18:50 +0200

#1428847 — [PATCH 6/8] nfs: don't use ->d_time

NFS is the most complicated of the lot.  It uses ->d_fsdata to

 1) store devname in the root dentry, and
 2) store nfs_unlinkdata for sillyrenames.

In addition it stores a verifier in ->d_time.

Introduce nfs_dentry structure that to store all of the above and make
d_fsdata point to it.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: Trond Myklebust <trond.myklebust@primarydata.com>
---
 fs/nfs/dir.c           | 18 ++++++++++++++----
 fs/nfs/getroot.c       |  4 ++--
 fs/nfs/namespace.c     |  2 +-
 fs/nfs/unlink.c        | 16 ++++++++--------
 include/linux/nfs_fs.h | 18 +++++++++++++++++-
 5 files changed, 42 insertions(+), 16 deletions(-)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index aaf7bd0cbae2..ebb536c23b19 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1022,7 +1022,7 @@ static int nfs_check_verifier(struct inode *dir, struct dentry *dentry,
 		return 1;
 	if (NFS_SERVER(dir)->flags & NFS_MOUNT_LOOKUP_CACHE_NONE)
 		return 0;
-	if (!nfs_verify_change_attribute(dir, dentry->d_time))
+	if (!nfs_verify_change_attribute(dir, NFS_D(dentry)->verf))
 		return 0;
 	/* Revalidate nfsi->cache_change_attribute before we declare a match */
 	if (rcu_walk)
@@ -1031,7 +1031,7 @@ static int nfs_check_verifier(struct inode *dir, struct dentry *dentry,
 		ret = nfs_revalidate_inode(NFS_SERVER(dir), dir);
 	if (ret < 0)
 		return 0;
-	if (!nfs_verify_change_attribute(dir, dentry->d_time))
+	if (!nfs_verify_change_attribute(dir, NFS_D(dentry)->verf))
 		return 0;
 	return 1;
 }
@@ -1339,15 +1339,23 @@ static void nfs_dentry_iput(struct dentry *dentry, struct inode *inode)
 	iput(inode);
 }
 
+static int nfs_d_allocate(struct dentry *dentry)
+{
+	dentry->d_fsdata = kzalloc(sizeof(struct nfs_dentry), GFP_KERNEL);
+
+	return dentry->d_fsdata ? 0 : -ENOMEM;
+}
+
 static void nfs_d_release(struct dentry *dentry)
 {
 	/* free cached devname value, if it survived that far */
-	if (unlikely(dentry->d_fsdata)) {
+	if (unlikely(NFS_D(dentry)->devname)) {
 		if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
 			WARN_ON(1);
 		else
-			kfree(dentry->d_fsdata);
+			kfree(NFS_D(dentry)->devname);
 	}
+	kfree(dentry->d_fsdata);
 }
 
 const struct dentry_operations nfs_dentry_operations = {
@@ -1356,6 +1364,7 @@ const struct dentry_operations nfs_dentry_operations = {
 	.d_delete	= nfs_dentry_delete,
 	.d_iput		= nfs_dentry_iput,
 	.d_automount	= nfs_d_automount,
+	.d_allocate	= nfs_d_allocate,
 	.d_release	= nfs_d_release,
 };
 EXPORT_SYMBOL_GPL(nfs_dentry_operations);
@@ -1437,6 +1446,7 @@ const struct dentry_operations nfs4_dentry_operations = {
 	.d_delete	= nfs_dentry_delete,
 	.d_iput		= nfs_dentry_iput,
 	.d_automount	= nfs_d_automount,
+	.d_allocate	= nfs_d_allocate,
 	.d_release	= nfs_d_release,
 };
 EXPORT_SYMBOL_GPL(nfs4_dentry_operations);
diff --git a/fs/nfs/getroot.c b/fs/nfs/getroot.c
index a608ffd28acc..84482c656e05 100644
--- a/fs/nfs/getroot.c
+++ b/fs/nfs/getroot.c
@@ -120,9 +120,9 @@ struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh,
 
 	security_d_instantiate(ret, inode);
 	spin_lock(&ret->d_lock);
-	if (IS_ROOT(ret) && !ret->d_fsdata &&
+	if (IS_ROOT(ret) && !NFS_D(ret)->devname &&
 	    !(ret->d_flags & DCACHE_NFSFS_RENAMED)) {
-		ret->d_fsdata = name;
+		NFS_D(ret)->devname = name;
 		name = NULL;
 	}
 	spin_unlock(&ret->d_lock);
diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
index c8162c660c44..0060806d047b 100644
--- a/fs/nfs/namespace.c
+++ b/fs/nfs/namespace.c
@@ -90,7 +90,7 @@ rename_retry:
 		*--end = '/';
 	}
 	*p = end;
-	base = dentry->d_fsdata;
+	base = NFS_D(dentry)->devname;
 	if (!base) {
 		spin_unlock(&dentry->d_lock);
 		rcu_read_unlock();
diff --git a/fs/nfs/unlink.c b/fs/nfs/unlink.c
index 1868246f56e6..d4c442a5f56a 100644
--- a/fs/nfs/unlink.c
+++ b/fs/nfs/unlink.c
@@ -134,8 +134,8 @@ static int nfs_call_unlink(struct dentry *dentry, struct nfs_unlinkdata *data)
 		spin_lock(&alias->d_lock);
 		if (d_really_is_positive(alias) &&
 		    !(alias->d_flags & DCACHE_NFSFS_RENAMED)) {
-			devname_garbage = alias->d_fsdata;
-			alias->d_fsdata = data;
+			devname_garbage = NFS_D(alias)->devname;
+			NFS_D(alias)->data = data;
 			alias->d_flags |= DCACHE_NFSFS_RENAMED;
 			ret = 1;
 		} else
@@ -189,8 +189,8 @@ nfs_async_unlink(struct dentry *dentry, struct qstr *name)
 	if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
 		goto out_unlock;
 	dentry->d_flags |= DCACHE_NFSFS_RENAMED;
-	devname_garbage = dentry->d_fsdata;
-	dentry->d_fsdata = data;
+	devname_garbage = NFS_D(dentry)->devname;
+	NFS_D(dentry)->data = data;
 	spin_unlock(&dentry->d_lock);
 	/*
 	 * If we'd displaced old cached devname, free it.  At that
@@ -226,8 +226,8 @@ nfs_complete_unlink(struct dentry *dentry, struct inode *inode)
 
 	spin_lock(&dentry->d_lock);
 	dentry->d_flags &= ~DCACHE_NFSFS_RENAMED;
-	data = dentry->d_fsdata;
-	dentry->d_fsdata = NULL;
+	data = NFS_D(dentry)->data;
+	NFS_D(dentry)->data = NULL;
 	spin_unlock(&dentry->d_lock);
 
 	if (NFS_STALE(inode) || !nfs_call_unlink(dentry, data))
@@ -240,10 +240,10 @@ nfs_cancel_async_unlink(struct dentry *dentry)
 {
 	spin_lock(&dentry->d_lock);
 	if (dentry->d_flags & DCACHE_NFSFS_RENAMED) {
-		struct nfs_unlinkdata *data = dentry->d_fsdata;
+		struct nfs_unlinkdata *data = NFS_D(dentry)->data;
 
 		dentry->d_flags &= ~DCACHE_NFSFS_RENAMED;
-		dentry->d_fsdata = NULL;
+		NFS_D(dentry)->data = NULL;
 		spin_unlock(&dentry->d_lock);
 		nfs_free_unlinkdata(data);
 		return;
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index d71278c3c5bd..a33fb67ddd1c 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -187,6 +187,17 @@ struct nfs_inode {
 };
 
 /*
+ * NFS specific dentry data
+ */
+struct nfs_dentry {
+	union {
+		char *devname;
+		struct nfs_unlinkdata *data;
+	};
+	unsigned long verf;
+};
+
+/*
  * Cache validity bit flags
  */
 #define NFS_INO_INVALID_ATTR	0x0001		/* cached attrs are invalid */
@@ -217,6 +228,11 @@ static inline struct nfs_inode *NFS_I(const struct inode *inode)
 	return container_of(inode, struct nfs_inode, vfs_inode);
 }
 
+static inline struct nfs_dentry *NFS_D(struct dentry *dentry)
+{
+	return (struct nfs_dentry *) dentry->d_fsdata;
+}
+
 static inline struct nfs_server *NFS_SB(const struct super_block *s)
 {
 	return (struct nfs_server *)(s->s_fs_info);
@@ -299,7 +315,7 @@ static inline int nfs_server_capable(struct inode *inode, int cap)
 
 static inline void nfs_set_verifier(struct dentry * dentry, unsigned long verf)
 {
-	dentry->d_time = verf;
+	NFS_D(dentry)->verf = verf;
 }
 
 /**
-- 
2.5.5

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#1428969

On Wed, Jun 22, 2016 at 04:35:08PM +0200, Miklos Szeredi wrote:
>  static void nfs_d_release(struct dentry *dentry)
>  {
>  	/* free cached devname value, if it survived that far */
> -	if (unlikely(dentry->d_fsdata)) {
> +	if (unlikely(NFS_D(dentry)->devname)) {
>  		if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
>  			WARN_ON(1);
>  		else
> -			kfree(dentry->d_fsdata);
> +			kfree(NFS_D(dentry)->devname);
>  	}
> +	kfree(dentry->d_fsdata);

Again, is that safe wrt RCU delays?

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