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Commit 294d71ff authored by Al Viro's avatar Al Viro
Browse files

new helper: __legitimize_mnt() 



same as legitimize_mnt(), except that it does *not* drop and regain
rcu_read_lock; return values are
0  =>  grabbed a reference, we are fine
1  =>  failed, just go away
-1 =>  failed, go away and mntput(bastard) when outside of rcu_read_lock

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 31956502

fs/mount.h

+1 −0
Original line number Diff line number Diff line
@@ -88,6 +88,7 @@ static inline int is_mounted(struct vfsmount *mnt) 
extern struct mount *__lookup_mnt(struct vfsmount *, struct dentry *);

extern struct mount *__lookup_mnt_last(struct vfsmount *, struct dentry *);



extern int __legitimize_mnt(struct vfsmount *, unsigned);

extern bool legitimize_mnt(struct vfsmount *, unsigned);



extern void __detach_mounts(struct dentry *dentry);

fs/namespace.c

+19 −8
Original line number Diff line number Diff line
@@ -590,24 +590,35 @@ static void delayed_free_vfsmnt(struct rcu_head *head) 
}



/* call under rcu_read_lock */

bool legitimize_mnt(struct vfsmount *bastard, unsigned seq)

int __legitimize_mnt(struct vfsmount *bastard, unsigned seq)

{

	struct mount *mnt;

	if (read_seqretry(&mount_lock, seq))

		return false;

		return 1;

	if (bastard == NULL)

		return true;

		return 0;

	mnt = real_mount(bastard);

	mnt_add_count(mnt, 1);

	if (likely(!read_seqretry(&mount_lock, seq)))

		return true;

		return 0;

	if (bastard->mnt_flags & MNT_SYNC_UMOUNT) {

		mnt_add_count(mnt, -1);

		return false;

		return 1;

	}

	return -1;

}



/* call under rcu_read_lock */

bool legitimize_mnt(struct vfsmount *bastard, unsigned seq)

{

	int res = __legitimize_mnt(bastard, seq);

	if (likely(!res))

		return true;

	if (unlikely(res < 0)) {

		rcu_read_unlock();

		mntput(bastard);

		rcu_read_lock();

	}

	return false;

}