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-rw-r--r--fs/namei.c50
1 files changed, 26 insertions, 24 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 1f844fb..cb0ebae 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -484,14 +484,12 @@ EXPORT_SYMBOL(path_put);
static inline void lock_rcu_walk(void)
{
- br_read_lock(&vfsmount_lock);
rcu_read_lock();
}
static inline void unlock_rcu_walk(void)
{
rcu_read_unlock();
- br_read_unlock(&vfsmount_lock);
}
/**
@@ -512,26 +510,23 @@ static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
BUG_ON(!(nd->flags & LOOKUP_RCU));
/*
- * Get a reference to the parent first: we're
- * going to make "path_put(nd->path)" valid in
- * non-RCU context for "terminate_walk()".
- *
- * If this doesn't work, return immediately with
- * RCU walking still active (and then we will do
- * the RCU walk cleanup in terminate_walk()).
+ * After legitimizing the bastards, terminate_walk()
+ * will do the right thing for non-RCU mode, and all our
+ * subsequent exit cases should rcu_read_unlock()
+ * before returning. Do vfsmount first; if dentry
+ * can't be legitimized, just set nd->path.dentry to NULL
+ * and rely on dput(NULL) being a no-op.
*/
- if (!lockref_get_not_dead(&parent->d_lockref))
+ if (!legitimize_mnt(nd->path.mnt, nd->m_seq))
return -ECHILD;
-
- /*
- * After the mntget(), we terminate_walk() will do
- * the right thing for non-RCU mode, and all our
- * subsequent exit cases should unlock_rcu_walk()
- * before returning.
- */
- mntget(nd->path.mnt);
nd->flags &= ~LOOKUP_RCU;
+ if (!lockref_get_not_dead(&parent->d_lockref)) {
+ nd->path.dentry = NULL;
+ unlock_rcu_walk();
+ return -ECHILD;
+ }
+
/*
* For a negative lookup, the lookup sequence point is the parents
* sequence point, and it only needs to revalidate the parent dentry.
@@ -608,16 +603,21 @@ static int complete_walk(struct nameidata *nd)
if (!(nd->flags & LOOKUP_ROOT))
nd->root.mnt = NULL;
+ if (!legitimize_mnt(nd->path.mnt, nd->m_seq)) {
+ unlock_rcu_walk();
+ return -ECHILD;
+ }
if (unlikely(!lockref_get_not_dead(&dentry->d_lockref))) {
unlock_rcu_walk();
+ mntput(nd->path.mnt);
return -ECHILD;
}
if (read_seqcount_retry(&dentry->d_seq, nd->seq)) {
unlock_rcu_walk();
dput(dentry);
+ mntput(nd->path.mnt);
return -ECHILD;
}
- mntget(nd->path.mnt);
unlock_rcu_walk();
}
@@ -909,15 +909,15 @@ int follow_up(struct path *path)
struct mount *parent;
struct dentry *mountpoint;
- br_read_lock(&vfsmount_lock);
+ read_seqlock_excl(&mount_lock);
parent = mnt->mnt_parent;
if (parent == mnt) {
- br_read_unlock(&vfsmount_lock);
+ read_sequnlock_excl(&mount_lock);
return 0;
}
mntget(&parent->mnt);
mountpoint = dget(mnt->mnt_mountpoint);
- br_read_unlock(&vfsmount_lock);
+ read_sequnlock_excl(&mount_lock);
dput(path->dentry);
path->dentry = mountpoint;
mntput(path->mnt);
@@ -1048,8 +1048,8 @@ static int follow_managed(struct path *path, unsigned flags)
/* Something is mounted on this dentry in another
* namespace and/or whatever was mounted there in this
- * namespace got unmounted before we managed to get the
- * vfsmount_lock */
+ * namespace got unmounted before lookup_mnt() could
+ * get it */
}
/* Handle an automount point */
@@ -1864,6 +1864,7 @@ static int path_init(int dfd, const char *name, unsigned int flags,
if (flags & LOOKUP_RCU) {
lock_rcu_walk();
nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
+ nd->m_seq = read_seqbegin(&mount_lock);
} else {
path_get(&nd->path);
}
@@ -1872,6 +1873,7 @@ static int path_init(int dfd, const char *name, unsigned int flags,
nd->root.mnt = NULL;
+ nd->m_seq = read_seqbegin(&mount_lock);
if (*name=='/') {
if (flags & LOOKUP_RCU) {
lock_rcu_walk();
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