Patch "kernfs: Add support for always empty directories." has been added to the 4.0-stable tree

PATCH [email protected] 1 participant 1 message Jul 10, 2015

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2015-07-10 16:54 UTC #0 lore raw

This is a note to let you know that I've just added the patch titled

kernfs: Add support for always empty directories.

to the 4.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kernfs-add-support-for-always-empty-directories.patch
and it can be found in the queue-4.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From ea015218f2f7ace2dad9cedd21ed95bdba2886d7 Mon Sep 17 00:00:00 2001

From: "Eric W. Biederman" <[email protected]>
Date: Wed, 13 May 2015 16:09:29 -0500
Subject: kernfs: Add support for always empty directories.

From: "Eric W. Biederman" <[email protected]>

commit ea015218f2f7ace2dad9cedd21ed95bdba2886d7 upstream.

Add a new function kernfs_create_empty_dir that can be used to create directory that can not be modified.

Update the code to use make_empty_dir_inode when reporting a permanently empty directory to the vfs.

Update the code to not allow adding to permanently empty directories.

Signed-off-by "Eric W. Biederman" <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 fs/kernfs/dir.c        |   38 +++++++++++++++++++++++++++++++++++++-
 fs/kernfs/inode.c      |    2 ++
 include/linux/kernfs.h |    3 +++
 3 files changed, 42 insertions(+), 1 deletion(-)

fs/kernfs/dir.c +37 -1

@@ -592,6 +592,9 @@ int kernfs_add_one(struct kernfs_node *k
 		goto out_unlock;
 
 	ret = -ENOENT;
+	if (parent->flags & KERNFS_EMPTY_DIR)
+		goto out_unlock;
+
 	if ((parent->flags & KERNFS_ACTIVATED) && !kernfs_active(parent))
 		goto out_unlock;

@@ -783,6 +786,38 @@ struct kernfs_node *kernfs_create_dir_ns
 	return ERR_PTR(rc);
 }
 
+/**
+ * kernfs_create_empty_dir - create an always empty directory
+ * @parent: parent in which to create a new directory
+ * @name: name of the new directory
+ *
+ * Returns the created node on success, ERR_PTR() value on failure.
+ */
+struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
+					    const char *name)
+{
+	struct kernfs_node *kn;
+	int rc;
+
+	/* allocate */
+	kn = kernfs_new_node(parent, name, S_IRUGO|S_IXUGO|S_IFDIR, KERNFS_DIR);
+	if (!kn)
+		return ERR_PTR(-ENOMEM);
+
+	kn->flags |= KERNFS_EMPTY_DIR;
+	kn->dir.root = parent->dir.root;
+	kn->ns = NULL;
+	kn->priv = NULL;
+
+	/* link in */
+	rc = kernfs_add_one(kn);
+	if (!rc)
+		return kn;
+
+	kernfs_put(kn);
+	return ERR_PTR(rc);
+}
+
 static struct dentry *kernfs_iop_lookup(struct inode *dir,
 					struct dentry *dentry,
 					unsigned int flags)

@@ -1254,7 +1289,8 @@ int kernfs_rename_ns(struct kernfs_node
 	mutex_lock(&kernfs_mutex);
 
 	error = -ENOENT;
-	if (!kernfs_active(kn) || !kernfs_active(new_parent))
+	if (!kernfs_active(kn) || !kernfs_active(new_parent) ||
+	    (new_parent->flags & KERNFS_EMPTY_DIR))
 		goto out;
 
 	error = 0;

fs/kernfs/inode.c +2 -0

@@ -296,6 +296,8 @@ static void kernfs_init_inode(struct ker
 	case KERNFS_DIR:
 		inode->i_op = &kernfs_dir_iops;
 		inode->i_fop = &kernfs_dir_fops;
+		if (kn->flags & KERNFS_EMPTY_DIR)
+			make_empty_dir_inode(inode);
 		break;
 	case KERNFS_FILE:
 		inode->i_size = kn->attr.size;

include/linux/kernfs.h +3 -0

@@ -45,6 +45,7 @@ enum kernfs_node_flag {
 	KERNFS_LOCKDEP		= 0x0100,
 	KERNFS_SUICIDAL		= 0x0400,
 	KERNFS_SUICIDED		= 0x0800,
+	KERNFS_EMPTY_DIR	= 0x1000,
 };
 
 /* @flags for kernfs_create_root() */

@@ -285,6 +286,8 @@ void kernfs_destroy_root(struct kernfs_r
 struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
 					 const char *name, umode_t mode,
 					 void *priv, const void *ns);
+struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
+					    const char *name);
 struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
 					 const char *name,
 					 umode_t mode, loff_t size,

Patches currently in stable-queue which might be from [email protected] are

queue-4.0/sysfs-create-mountpoints-with-sysfs_create_mount_point.patch queue-4.0/sysfs-add-support-for-permanently-empty-directories-to-serve-as-mount-points.patch queue-4.0/mnt-update-fs_fully_visible-to-test-for-permanently-empty-directories.patch queue-4.0/mnt-refactor-the-logic-for-mounting-sysfs-and-proc-in-a-user-namespace.patch queue-4.0/mnt-modify-fs_fully_visible-to-deal-with-locked-ro-nodev-and-atime.patch queue-4.0/fs-add-helper-functions-for-permanently-empty-directories.patch queue-4.0/sysctl-allow-creating-permanently-empty-directories-that-serve-as-mountpoints.patch queue-4.0/kernfs-add-support-for-always-empty-directories.patch queue-4.0/proc-allow-creating-permanently-empty-directories-that-serve-as-mount-points.patch