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Commit 73cd49ec authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Al Viro
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[patch 3/7] vfs: mountinfo: add mount ID 



Add a unique ID to each vfsmount using the IDR infrastructure.  The
identifiers are reused after the vfsmount is freed.

Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 9d1bc601

fs/namespace.c

+34 −0
Original line number Diff line number Diff line
@@ -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 +60,41 @@ static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) 


#define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16)



/* allocation is serialized by namespace_sem */

static int mnt_alloc_id(struct vfsmount *mnt)

{

	int res;



retry:

	ida_pre_get(&mnt_id_ida, GFP_KERNEL);

	spin_lock(&vfsmount_lock);

	res = ida_get_new(&mnt_id_ida, &mnt->mnt_id);

	spin_unlock(&vfsmount_lock);

	if (res == -EAGAIN)

		goto retry;



	return res;

}



static void mnt_free_id(struct vfsmount *mnt)

{

	spin_lock(&vfsmount_lock);

	ida_remove(&mnt_id_ida, mnt->mnt_id);

	spin_unlock(&vfsmount_lock);

}



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);
@@ -353,6 +386,7 @@ EXPORT_SYMBOL(simple_set_mnt); 
void free_vfsmnt(struct vfsmount *mnt)

{

	kfree(mnt->mnt_devname);

	mnt_free_id(mnt);

	kmem_cache_free(mnt_cache, mnt);

}

include/linux/mount.h

+1 −0
Original line number Diff line number Diff line
@@ -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