From: Miklos Szeredi <mszeredi@xxxxxxx>
Add a unique ID to each vfsmount using the IDR infrastructure. The
identifiers are reused after the vfsmount is freed.
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
---
fs/namespace.c | 20 ++++++++++++++++++++
include/linux/mount.h | 1 +
2 files changed, 21 insertions(+)
Index: vfs-2.6/fs/namespace.c
===================================================================
--- vfs-2.6.orig/fs/namespace.c 2008-03-27 12:05:55.000000000 +0100
+++ vfs-2.6/fs/namespace.c 2008-03-27 12:06:08.000000000 +0100
@@ -27,6 +27,7 @@
#include <linux/mount.h>
#include <linux/ramfs.h>
#include <linux/log2.h>
+#include <linux/idr.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
#include "pnode.h"
@@ -39,6 +40,7 @@
__cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock);
static int event;
+static DEFINE_IDA(mnt_id_ida);
static struct list_head *mount_hashtable __read_mostly;
static struct kmem_cache *mnt_cache __read_mostly;
@@ -58,10 +60,26 @@ static inline unsigned long hash(struct
#define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16)
+static int mnt_alloc_id(struct vfsmount *mnt)
+{
+ if (!ida_pre_get(&mnt_id_ida, GFP_KERNEL))
+ return -ENOMEM;
+
+ return ida_get_new_above(&mnt_id_ida, 1, &mnt->mnt_id);
+}
+
struct vfsmount *alloc_vfsmnt(const char *name)
{
struct vfsmount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
if (mnt) {
+ int err;
+
+ err = mnt_alloc_id(mnt);
+ if (err) {
+ kmem_cache_free(mnt_cache, mnt);
+ return NULL;
+ }
+
atomic_set(&mnt->mnt_count, 1);
INIT_LIST_HEAD(&mnt->mnt_hash);
INIT_LIST_HEAD(&mnt->mnt_child);
@@ -866,6 +884,8 @@ void umount_tree(struct vfsmount *mnt, i
p->mnt_mountpoint->d_mounted--;
}
change_mnt_propagation(p, MS_PRIVATE);
+ ida_remove(&mnt_id_ida, p->mnt_id);
+ p->mnt_id = 0;
}
}
Index: vfs-2.6/include/linux/mount.h
===================================================================
--- vfs-2.6.orig/include/linux/mount.h 2008-03-27 12:05:55.000000000 +0100
+++ vfs-2.6/include/linux/mount.h 2008-03-27 12:06:08.000000000 +0100
@@ -56,6 +56,7 @@ struct vfsmount {
struct list_head mnt_slave; /* slave list entry */
struct vfsmount *mnt_master; /* slave is on master->mnt_slave_list */
struct mnt_namespace *mnt_ns; /* containing namespace */
+ int mnt_id; /* mount identifier */
/*
* We put mnt_count & mnt_expiry_mark at the end of struct vfsmount
* to let these frequently modified fields in a separate cache line
--
--
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