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-rw-r--r--fs/namespace.c111
1 files changed, 81 insertions, 30 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index e6c234b1a645..487ba30bb5c6 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -96,10 +96,6 @@ static inline struct hlist_head *mp_hash(struct dentry *dentry)
return &mountpoint_hashtable[tmp & mp_hash_mask];
}
-/*
- * allocation is serialized by namespace_sem, but we need the spinlock to
- * serialize with freeing.
- */
static int mnt_alloc_id(struct mount *mnt)
{
int res;
@@ -678,7 +674,7 @@ out:
*
* lookup_mnt takes a reference to the found vfsmount.
*/
-struct vfsmount *lookup_mnt(struct path *path)
+struct vfsmount *lookup_mnt(const struct path *path)
{
struct mount *child_mnt;
struct vfsmount *m;
@@ -746,26 +742,50 @@ static struct mountpoint *lookup_mountpoint(struct dentry *dentry)
return NULL;
}
-static struct mountpoint *new_mountpoint(struct dentry *dentry)
+static struct mountpoint *get_mountpoint(struct dentry *dentry)
{
- struct hlist_head *chain = mp_hash(dentry);
- struct mountpoint *mp;
+ struct mountpoint *mp, *new = NULL;
int ret;
- mp = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
- if (!mp)
+ if (d_mountpoint(dentry)) {
+mountpoint:
+ read_seqlock_excl(&mount_lock);
+ mp = lookup_mountpoint(dentry);
+ read_sequnlock_excl(&mount_lock);
+ if (mp)
+ goto done;
+ }
+
+ if (!new)
+ new = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
+ if (!new)
return ERR_PTR(-ENOMEM);
+
+ /* Exactly one processes may set d_mounted */
ret = d_set_mounted(dentry);
- if (ret) {
- kfree(mp);
- return ERR_PTR(ret);
- }
- mp->m_dentry = dentry;
- mp->m_count = 1;
- hlist_add_head(&mp->m_hash, chain);
- INIT_HLIST_HEAD(&mp->m_list);
+ /* Someone else set d_mounted? */
+ if (ret == -EBUSY)
+ goto mountpoint;
+
+ /* The dentry is not available as a mountpoint? */
+ mp = ERR_PTR(ret);
+ if (ret)
+ goto done;
+
+ /* Add the new mountpoint to the hash table */
+ read_seqlock_excl(&mount_lock);
+ new->m_dentry = dentry;
+ new->m_count = 1;
+ hlist_add_head(&new->m_hash, mp_hash(dentry));
+ INIT_HLIST_HEAD(&new->m_list);
+ read_sequnlock_excl(&mount_lock);
+
+ mp = new;
+ new = NULL;
+done:
+ kfree(new);
return mp;
}
@@ -1034,6 +1054,8 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
if (IS_MNT_SLAVE(old))
list_add(&mnt->mnt_slave, &old->mnt_slave);
mnt->mnt_master = old->mnt_master;
+ } else {
+ CLEAR_MNT_SHARED(mnt);
}
if (flag & CL_MAKE_SHARED)
set_mnt_shared(mnt);
@@ -1159,7 +1181,36 @@ struct vfsmount *mntget(struct vfsmount *mnt)
}
EXPORT_SYMBOL(mntget);
-struct vfsmount *mnt_clone_internal(struct path *path)
+/* path_is_mountpoint() - Check if path is a mount in the current
+ * namespace.
+ *
+ * d_mountpoint() can only be used reliably to establish if a dentry is
+ * not mounted in any namespace and that common case is handled inline.
+ * d_mountpoint() isn't aware of the possibility there may be multiple
+ * mounts using a given dentry in a different namespace. This function
+ * checks if the passed in path is a mountpoint rather than the dentry
+ * alone.
+ */
+bool path_is_mountpoint(const struct path *path)
+{
+ unsigned seq;
+ bool res;
+
+ if (!d_mountpoint(path->dentry))
+ return false;
+
+ rcu_read_lock();
+ do {
+ seq = read_seqbegin(&mount_lock);
+ res = __path_is_mountpoint(path);
+ } while (read_seqretry(&mount_lock, seq));
+ rcu_read_unlock();
+
+ return res;
+}
+EXPORT_SYMBOL(path_is_mountpoint);
+
+struct vfsmount *mnt_clone_internal(const struct path *path)
{
struct mount *p;
p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE);
@@ -1568,11 +1619,11 @@ void __detach_mounts(struct dentry *dentry)
struct mount *mnt;
namespace_lock();
+ lock_mount_hash();
mp = lookup_mountpoint(dentry);
if (IS_ERR_OR_NULL(mp))
goto out_unlock;
- lock_mount_hash();
event++;
while (!hlist_empty(&mp->m_list)) {
mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list);
@@ -1582,9 +1633,9 @@ void __detach_mounts(struct dentry *dentry)
}
else umount_tree(mnt, UMOUNT_CONNECTED);
}
- unlock_mount_hash();
put_mountpoint(mp);
out_unlock:
+ unlock_mount_hash();
namespace_unlock();
}
@@ -1758,7 +1809,7 @@ out:
/* Caller should check returned pointer for errors */
-struct vfsmount *collect_mounts(struct path *path)
+struct vfsmount *collect_mounts(const struct path *path)
{
struct mount *tree;
namespace_lock();
@@ -1791,7 +1842,7 @@ void drop_collected_mounts(struct vfsmount *mnt)
*
* Release with mntput().
*/
-struct vfsmount *clone_private_mount(struct path *path)
+struct vfsmount *clone_private_mount(const struct path *path)
{
struct mount *old_mnt = real_mount(path->mnt);
struct mount *new_mnt;
@@ -1799,9 +1850,7 @@ struct vfsmount *clone_private_mount(struct path *path)
if (IS_MNT_UNBINDABLE(old_mnt))
return ERR_PTR(-EINVAL);
- down_read(&namespace_sem);
new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE);
- up_read(&namespace_sem);
if (IS_ERR(new_mnt))
return ERR_CAST(new_mnt);
@@ -2013,9 +2062,7 @@ retry:
namespace_lock();
mnt = lookup_mnt(path);
if (likely(!mnt)) {
- struct mountpoint *mp = lookup_mountpoint(dentry);
- if (!mp)
- mp = new_mountpoint(dentry);
+ struct mountpoint *mp = get_mountpoint(dentry);
if (IS_ERR(mp)) {
namespace_unlock();
inode_unlock(dentry->d_inode);
@@ -2034,7 +2081,11 @@ retry:
static void unlock_mount(struct mountpoint *where)
{
struct dentry *dentry = where->m_dentry;
+
+ read_seqlock_excl(&mount_lock);
put_mountpoint(where);
+ read_sequnlock_excl(&mount_lock);
+
namespace_unlock();
inode_unlock(dentry->d_inode);
}
@@ -2997,7 +3048,7 @@ bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
}
-bool path_is_under(struct path *path1, struct path *path2)
+bool path_is_under(const struct path *path1, const struct path *path2)
{
bool res;
read_seqlock_excl(&mount_lock);
@@ -3110,9 +3161,9 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
touch_mnt_namespace(current->nsproxy->mnt_ns);
/* A moved mount should not expire automatically */
list_del_init(&new_mnt->mnt_expire);
+ put_mountpoint(root_mp);
unlock_mount_hash();
chroot_fs_refs(&root, &new);
- put_mountpoint(root_mp);
error = 0;
out4:
unlock_mount(old_mp);
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-28 18:58:02 +0000