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authorAl Viro <viro@zeniv.linux.org.uk>2017-12-25 19:43:35 -0500
committerAl Viro <viro@zeniv.linux.org.uk>2018-01-05 11:54:37 -0500
commit36735a6a2b5e042db1af956ce4bcc13f3ff99e21 (patch)
treece8d6eddf34be533c2c12d6f68f916b9fb3dd035 /ipc/mqueue.c
parenttidy do_mq_open() up a bit (diff)
downloadlinux-dev-36735a6a2b5e042db1af956ce4bcc13f3ff99e21.tar.xz
linux-dev-36735a6a2b5e042db1af956ce4bcc13f3ff99e21.zip
mqueue: switch to on-demand creation of internal mount
Instead of doing that upon each ipcns creation, we do that the first time mq_open(2) or mqueue mount is done in an ipcns. What's more, doing that allows to get rid of mount_ns() use - we can go with considerably cheaper mount_nodev(), avoiding the loop over all mqueue superblock instances; ipcns->mq_mnt is used to locate preexisting instance in O(1) time instead of O(instances) mount_ns() would've cost us. Based upon the version by Giuseppe Scrivano <gscrivan@redhat.com>; I've added handling of userland mqueue mounts (original had been broken in that area) and added a switch to mount_nodev(). Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'ipc/mqueue.c')
-rw-r--r--ipc/mqueue.c74
1 files changed, 55 insertions, 19 deletions
diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 9f05837a86a6..738579191fd2 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -325,8 +325,9 @@ err:
static int mqueue_fill_super(struct super_block *sb, void *data, int silent)
{
struct inode *inode;
- struct ipc_namespace *ns = sb->s_fs_info;
+ struct ipc_namespace *ns = data;
+ sb->s_fs_info = ns;
sb->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;
sb->s_blocksize = PAGE_SIZE;
sb->s_blocksize_bits = PAGE_SHIFT;
@@ -343,18 +344,44 @@ static int mqueue_fill_super(struct super_block *sb, void *data, int silent)
return 0;
}
+static struct file_system_type mqueue_fs_type;
+/*
+ * Return value is pinned only by reference in ->mq_mnt; it will
+ * live until ipcns dies. Caller does not need to drop it.
+ */
+static struct vfsmount *mq_internal_mount(void)
+{
+ struct ipc_namespace *ns = current->nsproxy->ipc_ns;
+ struct vfsmount *m = ns->mq_mnt;
+ if (m)
+ return m;
+ m = kern_mount_data(&mqueue_fs_type, ns);
+ spin_lock(&mq_lock);
+ if (unlikely(ns->mq_mnt)) {
+ spin_unlock(&mq_lock);
+ if (!IS_ERR(m))
+ kern_unmount(m);
+ return ns->mq_mnt;
+ }
+ if (!IS_ERR(m))
+ ns->mq_mnt = m;
+ spin_unlock(&mq_lock);
+ return m;
+}
+
static struct dentry *mqueue_mount(struct file_system_type *fs_type,
int flags, const char *dev_name,
void *data)
{
- struct ipc_namespace *ns;
- if (flags & SB_KERNMOUNT) {
- ns = data;
- data = NULL;
- } else {
- ns = current->nsproxy->ipc_ns;
- }
- return mount_ns(fs_type, flags, data, ns, ns->user_ns, mqueue_fill_super);
+ struct vfsmount *m;
+ if (flags & SB_KERNMOUNT)
+ return mount_nodev(fs_type, flags, data, mqueue_fill_super);
+ m = mq_internal_mount();
+ if (IS_ERR(m))
+ return ERR_CAST(m);
+ atomic_inc(&m->mnt_sb->s_active);
+ down_write(&m->mnt_sb->s_umount);
+ return dget(m->mnt_root);
}
static void init_once(void *foo)
@@ -743,13 +770,16 @@ static int prepare_open(struct dentry *dentry, int oflag, int ro,
static int do_mq_open(const char __user *u_name, int oflag, umode_t mode,
struct mq_attr *attr)
{
- struct vfsmount *mnt = current->nsproxy->ipc_ns->mq_mnt;
- struct dentry *root = mnt->mnt_root;
+ struct vfsmount *mnt = mq_internal_mount();
+ struct dentry *root;
struct filename *name;
struct path path;
int fd, error;
int ro;
+ if (IS_ERR(mnt))
+ return PTR_ERR(mnt);
+
audit_mq_open(oflag, mode, attr);
if (IS_ERR(name = getname(u_name)))
@@ -760,6 +790,7 @@ static int do_mq_open(const char __user *u_name, int oflag, umode_t mode,
goto out_putname;
ro = mnt_want_write(mnt); /* we'll drop it in any case */
+ root = mnt->mnt_root;
inode_lock(d_inode(root));
path.dentry = lookup_one_len(name->name, root, strlen(name->name));
if (IS_ERR(path.dentry)) {
@@ -808,6 +839,9 @@ SYSCALL_DEFINE1(mq_unlink, const char __user *, u_name)
struct ipc_namespace *ipc_ns = current->nsproxy->ipc_ns;
struct vfsmount *mnt = ipc_ns->mq_mnt;
+ if (!mnt)
+ return -ENOENT;
+
name = getname(u_name);
if (IS_ERR(name))
return PTR_ERR(name);
@@ -1534,28 +1568,26 @@ int mq_init_ns(struct ipc_namespace *ns)
ns->mq_msgsize_max = DFLT_MSGSIZEMAX;
ns->mq_msg_default = DFLT_MSG;
ns->mq_msgsize_default = DFLT_MSGSIZE;
+ ns->mq_mnt = NULL;
- ns->mq_mnt = kern_mount_data(&mqueue_fs_type, ns);
- if (IS_ERR(ns->mq_mnt)) {
- int err = PTR_ERR(ns->mq_mnt);
- ns->mq_mnt = NULL;
- return err;
- }
return 0;
}
void mq_clear_sbinfo(struct ipc_namespace *ns)
{
- ns->mq_mnt->mnt_sb->s_fs_info = NULL;
+ if (ns->mq_mnt)
+ ns->mq_mnt->mnt_sb->s_fs_info = NULL;
}
void mq_put_mnt(struct ipc_namespace *ns)
{
- kern_unmount(ns->mq_mnt);
+ if (ns->mq_mnt)
+ kern_unmount(ns->mq_mnt);
}
static int __init init_mqueue_fs(void)
{
+ struct vfsmount *m;
int error;
mqueue_inode_cachep = kmem_cache_create("mqueue_inode_cache",
@@ -1577,6 +1609,10 @@ static int __init init_mqueue_fs(void)
if (error)
goto out_filesystem;
+ m = kern_mount_data(&mqueue_fs_type, &init_ipc_ns);
+ if (IS_ERR(m))
+ goto out_filesystem;
+ init_ipc_ns.mq_mnt = m;
return 0;
out_filesystem: