This is a note to let you know that I've just added the patch titled
kernfs: introduce kernfs_pin_sb()
to the 3.15-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-introduce-kernfs_pin_sb.patch
and it can be found in the queue-3.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 4e26445faad366d67d7723622bf6a60a6f0f5993 Mon Sep 17 00:00:00 2001
From: Li Zefan <lizefan@xxxxxxxxxx>
Date: Mon, 30 Jun 2014 11:50:28 +0800
Subject: kernfs: introduce kernfs_pin_sb()
From: Li Zefan <lizefan@xxxxxxxxxx>
commit 4e26445faad366d67d7723622bf6a60a6f0f5993 upstream.
kernfs_pin_sb() tries to get a refcnt of the superblock.
This will be used by cgroupfs.
v2:
- make kernfs_pin_sb() return the superblock.
- drop kernfs_drop_sb().
tj: Updated the comment a bit.
[ This is a prerequisite for a bugfix. ]
Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Li Zefan <lizefan@xxxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/kernfs/mount.c | 30 ++++++++++++++++++++++++++++++
include/linux/kernfs.h | 1 +
2 files changed, 31 insertions(+)
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -211,6 +211,36 @@ void kernfs_kill_sb(struct super_block *
kernfs_put(root_kn);
}
+/**
+ * kernfs_pin_sb: try to pin the superblock associated with a kernfs_root
+ * @kernfs_root: the kernfs_root in question
+ * @ns: the namespace tag
+ *
+ * Pin the superblock so the superblock won't be destroyed in subsequent
+ * operations. This can be used to block ->kill_sb() which may be useful
+ * for kernfs users which dynamically manage superblocks.
+ *
+ * Returns NULL if there's no superblock associated to this kernfs_root, or
+ * -EINVAL if the superblock is being freed.
+ */
+struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns)
+{
+ struct kernfs_super_info *info;
+ struct super_block *sb = NULL;
+
+ mutex_lock(&kernfs_mutex);
+ list_for_each_entry(info, &root->supers, node) {
+ if (info->ns == ns) {
+ sb = info->sb;
+ if (!atomic_inc_not_zero(&info->sb->s_active))
+ sb = ERR_PTR(-EINVAL);
+ break;
+ }
+ }
+ mutex_unlock(&kernfs_mutex);
+ return sb;
+}
+
void __init kernfs_init(void)
{
kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -304,6 +304,7 @@ struct dentry *kernfs_mount_ns(struct fi
struct kernfs_root *root, unsigned long magic,
bool *new_sb_created, const void *ns);
void kernfs_kill_sb(struct super_block *sb);
+struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns);
void kernfs_init(void);
Patches currently in stable-queue which might be from lizefan@xxxxxxxxxx are
queue-3.15/kernfs-introduce-kernfs_pin_sb.patch
queue-3.15/cgroup-fix-mount-failure-in-a-corner-case.patch
queue-3.15/cpuset-mempolicy-fix-sleeping-function-called-from-invalid-context.patch
queue-3.15/kernfs-implement-kernfs_root-supers-list.patch
queue-3.15/cgroup-fix-a-race-between-cgroup_mount-and-cgroup_kill_sb.patch
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