linux-kernel - [PATCH V2 05/12] kernfs: introduce kernfs_node

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Date:   Wed, 14 Jun 2017 09:12:03 -0700
From:   Shaohua Li <shli@...nel.org>
To:     linux-kernel@...r.kernel.org, linux-block@...r.kernel.org
Cc:     tj@...nel.org, gregkh@...uxfoundation.org, hch@....de,
        axboe@...com, rostedt@...dmis.org, lizefan@...wei.com,
        Kernel-team@...com, Shaohua Li <shli@...com>
Subject: [PATCH V2 05/12] kernfs: introduce kernfs_node_id

From: Shaohua Li <shli@...com>

inode number and generation can identify a kernfs node. We are going to
export the identification by exportfs operations, so put ino and
generation into a separate structure. It's convenient when later patches
use the identification.

Please note, I extend inode number to 64 bits. idr actually doesn't
support 64-bit yet, so currently inode number is always 32-bit. Tejun
has concerns 32-bit inode and generation could wrap. We will need to fix
this later. The data structure will be exported out to userspace, so the
goal of the 64-bit data structure is to avoid change the data structure
if we make inode number to 64-bit later.

Signed-off-by: Shaohua Li <shli@...com>
---
 fs/kernfs/dir.c        | 10 +++++-----
 fs/kernfs/file.c       |  4 ++--
 fs/kernfs/inode.c      |  4 ++--
 include/linux/cgroup.h |  2 +-
 include/linux/kernfs.h |  9 +++++++--
 5 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index e54fdd9..7483bea 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -539,7 +539,7 @@ void kernfs_put(struct kernfs_node *kn)
 	}
 	kfree(kn->iattr);
 	spin_lock(&kernfs_idr_lock);
-	idr_remove(&root->ino_idr, kn->ino);
+	idr_remove(&root->ino_idr, kn->id.ino);
 	spin_unlock(&kernfs_idr_lock);
 	kmem_cache_free(kernfs_node_cache, kn);
 
@@ -639,8 +639,8 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
 	idr_preload_end();
 	if (ret < 0)
 		goto err_out2;
-	kn->ino = ret;
-	kn->generation = atomic_inc_return(&root->next_generation);
+	kn->id.ino = ret;
+	kn->id.generation = atomic_inc_return(&root->next_generation);
 
 	/* set ino first. Above atomic_inc_return has a barrier */
 	atomic_set(&kn->count, 1);
@@ -711,7 +711,7 @@ struct kernfs_node *kernfs_find_and_get_node_by_ino(struct kernfs_root *root,
 	 * 'ino' should be uptodate, hence we can use 'ino' to filter stale
 	 * node.
 	 */
-	if (kn->ino != ino)
+	if (kn->id.ino != ino)
 		goto out;
 	rcu_read_unlock();
 
@@ -1644,7 +1644,7 @@ static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx)
 		const char *name = pos->name;
 		unsigned int type = dt_type(pos);
 		int len = strlen(name);
-		ino_t ino = pos->ino;
+		ino_t ino = pos->id.ino;
 
 		ctx->pos = pos->hash;
 		file->private_data = pos;
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 7f90d4d..7441925 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -895,7 +895,7 @@ static void kernfs_notify_workfn(struct work_struct *work)
 		 * have the matching @file available.  Look up the inodes
 		 * and generate the events manually.
 		 */
-		inode = ilookup(info->sb, kn->ino);
+		inode = ilookup(info->sb, kn->id.ino);
 		if (!inode)
 			continue;
 
@@ -903,7 +903,7 @@ static void kernfs_notify_workfn(struct work_struct *work)
 		if (parent) {
 			struct inode *p_inode;
 
-			p_inode = ilookup(info->sb, parent->ino);
+			p_inode = ilookup(info->sb, parent->id.ino);
 			if (p_inode) {
 				fsnotify(p_inode, FS_MODIFY | FS_EVENT_ON_CHILD,
 					 inode, FSNOTIFY_EVENT_INODE, kn->name, 0);
diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c
index 4c8b510..a343039 100644
--- a/fs/kernfs/inode.c
+++ b/fs/kernfs/inode.c
@@ -220,7 +220,7 @@ static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
 	inode->i_private = kn;
 	inode->i_mapping->a_ops = &kernfs_aops;
 	inode->i_op = &kernfs_iops;
-	inode->i_generation = kn->generation;
+	inode->i_generation = kn->id.generation;
 
 	set_default_inode_attr(inode, kn->mode);
 	kernfs_refresh_inode(kn, inode);
@@ -266,7 +266,7 @@ struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
 {
 	struct inode *inode;
 
-	inode = iget_locked(sb, kn->ino);
+	inode = iget_locked(sb, kn->id.ino);
 	if (inode && (inode->i_state & I_NEW))
 		kernfs_init_inode(kn, inode);
 
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 710a005..30c6877 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -543,7 +543,7 @@ static inline bool cgroup_is_populated(struct cgroup *cgrp)
 /* returns ino associated with a cgroup */
 static inline ino_t cgroup_ino(struct cgroup *cgrp)
 {
-	return cgrp->kn->ino;
+	return cgrp->kn->id.ino;
 }
 
 /* cft/css accessors for cftype->write() operation */
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 61668d1..6be2d57 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -95,6 +95,12 @@ struct kernfs_elem_attr {
 	struct kernfs_node	*notify_next;	/* for kernfs_notify() */
 };
 
+/* represent a kernfs node */
+struct kernfs_node_id {
+	u64			ino;
+	u32			generation;
+} __attribute__((packed));
+
 /*
  * kernfs_node - the building block of kernfs hierarchy.  Each and every
  * kernfs node is represented by single kernfs_node.  Most fields are
@@ -131,11 +137,10 @@ struct kernfs_node {
 
 	void			*priv;
 
+	struct kernfs_node_id	id;
 	unsigned short		flags;
 	umode_t			mode;
-	unsigned int		ino;
 	struct kernfs_iattrs	*iattr;
-	u32			generation;
 };
 
 /*
-- 
2.9.3