[PATCH 3.15 69/84] kernfs: implement kernfs_root->supers list

Greg Kroah-Hartman
2014-07-15T23:31:55Z

From: Tejun Heo <tj@kernel.org>

commit 7d568a8383bbb9c1f5167781075906acb2bb1550 upstream.

Currently, there's no way to find out which super_blocks are
associated with a given kernfs_root. Let's implement it - the planned
inotify extension to kernfs_notify() needs it.

Make kernfs_super_info point back to the super_block and chain it at
kernfs_root->supers.

Signed-off-by: Tejun Heo <tj@kernel.org>
[lizf: Backported to 3.15: Adjust context]
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/kernfs/dir.c | 1 +
fs/kernfs/kernfs-internal.h | 5 +++++
fs/kernfs/mount.c | 11 +++++++++++
include/linux/kernfs.h | 4 ++++
4 files changed, 21 insertions(+)

--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -714,6 +714,7 @@ struct kernfs_root *kernfs_create_root(s
return ERR_PTR(-ENOMEM);

ida_init(&root->ino_ida);
+ INIT_LIST_HEAD(&root->supers);

kn = __kernfs_new_node(root, "", S_IFDIR | S_IRUGO | S_IXUGO,
KERNFS_DIR);
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -49,6 +49,8 @@ static inline struct kernfs_root *kernfs
* mount.c
*/
struct kernfs_super_info {
+ struct super_block *sb;
+
/*
* The root associated with this super_block. Each super_block is
* identified by the root and ns it's associated with.
@@ -62,6 +64,9 @@ struct kernfs_super_info {
* an array and compare kernfs_node tag against every entry.
*/
const void *ns;
+
+ /* anchored at kernfs_root->supers, protected by kernfs_mutex */
+ struct list_head node;
};
#define kernfs_info(SB) ((struct kernfs_super_info *)(SB->s_fs_info))

--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -68,6 +68,7 @@ static int kernfs_fill_super(struct supe
struct inode *inode;
struct dentry *root;

+ info->sb = sb;
sb->s_blocksize = PAGE_CACHE_SIZE;
sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
sb->s_magic = magic;
@@ -167,12 +168,18 @@ struct dentry *kernfs_mount_ns(struct fi
*new_sb_created = !sb->s_root;

if (!sb->s_root) {
+ struct kernfs_super_info *info = kernfs_info(sb);
+
error = kernfs_fill_super(sb, magic);
if (error) {
deactivate_locked_super(sb);
return ERR_PTR(error);
}
sb->s_flags |= MS_ACTIVE;
+
+ mutex_lock(&kernfs_mutex);
+ list_add(&info->node, &root->supers);
+ mutex_unlock(&kernfs_mutex);
}

return dget(sb->s_root);
@@ -191,6 +198,10 @@ void kernfs_kill_sb(struct super_block *
struct kernfs_super_info *info = kernfs_info(sb);
struct kernfs_node *root_kn = sb->s_root->d_fsdata;

+ mutex_lock(&kernfs_mutex);
+ list_del(&info->node);
+ mutex_unlock(&kernfs_mutex);
+
/*
* Remove the superblock from fs_supers/s_instances
* so we can't find it, before freeing kernfs_super_info.
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -161,6 +161,10 @@ struct kernfs_root {
/* private fields, do not use outside kernfs proper */
struct ida ino_ida;
struct kernfs_syscall_ops *syscall_ops;
+
+ /* list of kernfs_super_info of this root, protected by kernfs_mutex */
+ struct list_head supers;
+
wait_queue_head_t deactivate_waitq;
};