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Date: Wed, 17 Dec 2008 13:25:21 -0800
From: Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
To: "Serge E. Hallyn" <serue@...ibm.com>
Cc: lkml <linux-kernel@...r.kernel.org>,
Linux Containers <containers@...ts.osdl.org>
Subject: Re: [PATCH 2/2] ipc namespaces: implement support for posix
msqueues
Just a couple of nits.
Serge E. Hallyn [serue@...ibm.com] wrote:
| Implement multiple mounts of the mqueue file system, and
| link it to usage of CLONE_NEWIPC.
|
| Each ipc ns has a corresponding mqueuefs superblock. When
| a user does clone(CLONE_NEWIPC) or unshare(CLONE_NEWIPC), the
| unshare will cause an internal mount of a new mqueuefs sb
| linked to the new ipc ns.
|
| When a user does 'mount -t mqueue mqueue /dev/mqueue', he
| mounts the mqueuefs superblock.
|
| Posix message queues can be worked with both through the
| mq_* system calls (see mq_overview(7)), and through the VFS
| through the mqueue mount. Any usage of mq_open() and friends
| will work with the acting task's ipc namespace. Any actions
| through the VFS will work with the mqueuefs in which the
| file was created. So if a user doesn't remount mqueuefs
| after unshare(CLONE_NEWIPC), mq_open("/ab") will not be
| reflected in "ls /dev/mqueue".
|
| If task a mounts mqueue for ipc_ns:1, then clones task b with
| a new ipcns, ipcns:2, and then task a is the last task in
| ipc_ns:1 to exit, then (1) ipc_ns:1 will be freed, (2) it's
| superblock will live on until task b umounts the corresponding
| mqueuefs, and vfs actions will continue to succeed, but (3)
| sb->s_fs_info will be NULL for the sb corresponding to the
| deceased ipc_ns:1.
|
| Changelog:
| Dec 17: removed unused static fn (get_ipcns_from_sb)
|
| Signed-off-by: Cedric Le Goater <clg@...ibm.com>
| Signed-off-by: Serge E. Hallyn <serue@...ibm.com>
| ---
| include/linux/ipc_namespace.h | 16 ++---
| ipc/mqueue.c | 140 ++++++++++++++++++++++++++++++++---------
| ipc/msgutil.c | 8 +--
| ipc/namespace.c | 25 ++++++--
| ipc/util.h | 6 +-
| 5 files changed, 144 insertions(+), 51 deletions(-)
|
| diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
| index 532598f..74f1ae2 100644
| --- a/include/linux/ipc_namespace.h
| +++ b/include/linux/ipc_namespace.h
| @@ -25,7 +25,7 @@ struct ipc_ids {
| };
|
| struct ipc_namespace {
| - struct kref kref;
| + atomic_t count;
| struct ipc_ids ids[3];
|
| int sem_ctls[4];
| @@ -56,6 +56,7 @@ struct ipc_namespace {
| extern struct ipc_namespace init_ipc_ns;
| extern atomic_t nr_ipc_ns;
|
| +extern spinlock_t mq_lock;
| #if defined(CONFIG_POSIX_MQUEUE) || defined(CONFIG_SYSVIPC)
| #define INIT_IPC_NS(ns) .ns = &init_ipc_ns,
| #else
| @@ -75,18 +76,18 @@ extern int ipcns_notify(unsigned long);
| #endif /* CONFIG_SYSVIPC */
|
| #ifdef CONFIG_POSIX_MQUEUE
| -extern void mq_init_ns(struct ipc_namespace *ns);
| +extern int mq_init_ns(struct ipc_namespace *ns);
| /* default values */
| #define DFLT_QUEUESMAX 256 /* max number of message queues */
| #define DFLT_MSGMAX 10 /* max number of messages in each queue */
| #define HARD_MSGMAX (131072/sizeof(void *))
| #define DFLT_MSGSIZEMAX 8192 /* max message size */
| #else
| -#define mq_init_ns(ns)
| +#define mq_init_ns(ns) (0)
| #endif
|
| #if defined(CONFIG_IPC_NS)
| -extern void free_ipc_ns(struct kref *kref);
| +extern void free_ipc_ns(struct ipc_namespace *ns);
| extern struct ipc_namespace *copy_ipcs(unsigned long flags,
| struct ipc_namespace *ns);
| extern void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
| @@ -96,14 +97,11 @@ extern void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
| static inline struct ipc_namespace *get_ipc_ns(struct ipc_namespace *ns)
| {
| if (ns)
| - kref_get(&ns->kref);
| + atomic_inc(&ns->count);
| return ns;
| }
|
| -static inline void put_ipc_ns(struct ipc_namespace *ns)
| -{
| - kref_put(&ns->kref, free_ipc_ns);
| -}
| +extern void put_ipc_ns(struct ipc_namespace *ns);
| #else
| static inline struct ipc_namespace *copy_ipcs(unsigned long flags,
| struct ipc_namespace *ns)
| diff --git a/ipc/mqueue.c b/ipc/mqueue.c
| index 01d64a0..6b235c1 100644
| --- a/ipc/mqueue.c
| +++ b/ipc/mqueue.c
| @@ -88,7 +88,6 @@ static const struct file_operations mqueue_file_operations;
| static struct super_operations mqueue_super_ops;
| static void remove_notification(struct mqueue_inode_info *info);
|
| -static spinlock_t mq_lock;
| static struct kmem_cache *mqueue_inode_cachep;
|
| static struct ctl_table_header * mq_sysctl_table;
| @@ -98,25 +97,30 @@ static inline struct mqueue_inode_info *MQUEUE_I(struct inode *inode)
| return container_of(inode, struct mqueue_inode_info, vfs_inode);
| }
|
| -void mq_init_ns(struct ipc_namespace *ns) {
| - ns->mq_queues_count = 0;
| - ns->mq_queues_max = DFLT_QUEUESMAX;
| - ns->mq_msg_max = DFLT_MSGMAX;
| - ns->mq_msgsize_max = DFLT_MSGSIZEMAX;
| - ns->mq_mnt = mntget(init_ipc_ns.mq_mnt);
| +/*
| + * This routine should be called with the mq_lock held.
| + */
| +static inline struct ipc_namespace *__get_ns_from_ino(struct inode *inode)
Nit. Lot of places in kernel use 'ino' to represent the numeric inode number.
Maybe better to name get_ns_from_inode().
| +{
| + return get_ipc_ns(inode->i_sb->s_fs_info);
| }
|
| -void mq_exit_ns(struct ipc_namespace *ns) {
| - /* will need to clear out ns->mq_mnt->mnt_sb->s_fs_info here */
| - mntput(ns->mq_mnt);
| +static inline struct ipc_namespace *get_ns_from_ino(struct inode *inode)
| +{
| + struct ipc_namespace *ns;
| +
| + spin_lock(&mq_lock);
| + ns = __get_ns_from_ino(inode);
| + spin_unlock(&mq_lock);
| + return ns;
| }
|
| -static struct inode *mqueue_get_inode(struct super_block *sb, int mode,
| - struct mq_attr *attr)
| +static struct inode *mqueue_get_inode(struct super_block *sb,
| + struct ipc_namespace *ipc_ns, int mode,
| + struct mq_attr *attr)
| {
| struct user_struct *u = current_user();
| struct inode *inode;
| - struct ipc_namespace *ipc_ns = &init_ipc_ns;
|
| inode = new_inode(sb);
| if (inode) {
| @@ -192,30 +196,76 @@ out_inode:
| static int mqueue_fill_super(struct super_block *sb, void *data, int silent)
| {
| struct inode *inode;
| + struct ipc_namespace *ns = data;
| + int error = 0;
|
| sb->s_blocksize = PAGE_CACHE_SIZE;
| sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
| sb->s_magic = MQUEUE_MAGIC;
| sb->s_op = &mqueue_super_ops;
|
| - inode = mqueue_get_inode(sb, S_IFDIR | S_ISVTX | S_IRWXUGO, NULL);
| - if (!inode)
| - return -ENOMEM;
| + inode = mqueue_get_inode(sb, ns, S_IFDIR | S_ISVTX | S_IRWXUGO,
| + NULL);
| + if (!inode) {
| + error = -ENOMEM;
| + goto out;
| + }
|
| sb->s_root = d_alloc_root(inode);
| if (!sb->s_root) {
| iput(inode);
| - return -ENOMEM;
| + error = -ENOMEM;
| }
|
| - return 0;
| +out:
| + return error;
| +}
| +
| +static int compare_sb_single_ns(struct super_block *sb, void *data)
| +{
| + return sb->s_fs_info == data;
| +}
| +
| +static int set_sb_single_ns(struct super_block *sb, void *data)
| +{
| + sb->s_fs_info = data;
| + return set_anon_super(sb, NULL);
| +}
| +
| +static int get_sb_single_ns(struct file_system_type *fs_type,
| + int flags, void *data,
| + int (*fill_super)(struct super_block *, void *, int),
| + struct vfsmount *mnt)
| +{
| + struct super_block *s;
| + int error;
| +
| + s = sget(fs_type, compare_sb_single_ns, set_sb_single_ns, data);
| + if (IS_ERR(s))
| + return PTR_ERR(s);
| + if (!s->s_root) {
| + s->s_flags = flags;
| + error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
| + if (error) {
| + up_write(&s->s_umount);
| + deactivate_super(s);
| + return error;
| + }
| + s->s_flags |= MS_ACTIVE;
| + }
| + do_remount_sb(s, flags, data, 0);
| + return simple_set_mnt(mnt, s);
| }
|
| static int mqueue_get_sb(struct file_system_type *fs_type,
| int flags, const char *dev_name,
| void *data, struct vfsmount *mnt)
| {
| - return get_sb_single(fs_type, flags, data, mqueue_fill_super, mnt);
| + if (flags & MS_KERNMOUNT)
| + return get_sb_single_ns(fs_type, flags, data,
| + mqueue_fill_super, mnt);
| + return get_sb_single_ns(fs_type, flags, current->nsproxy->ipc_ns,
| + mqueue_fill_super, mnt);
nit. This maybe easier to read with an ns local variable and a single
call to get_sb_single_ns().
Suka
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