ipc: Convert mqueue fs to fs_context

Convert the mqueue filesystem to use the filesystem context stuff.

Notes:

 (1) The relevant ipc namespace is selected in when the context is
     initialised (and it defaults to the current task's ipc namespace).
     The caller can override this before calling vfs_get_tree().

 (2) Rather than simply calling kern_mount_data(), mq_init_ns() and
     mq_internal_mount() create a context, adjust it and then do the rest
     of the mount procedure.

 (3) The lazy mqueue mounting on creation of a new namespace is retained
     from a previous patch, but the avoidance of sget() if no superblock
     yet exists is reverted and the superblock is again keyed on the
     namespace pointer.

     Yes, there was a performance gain in not searching the superblock
     hash, but it's only paid once per ipc namespace - and only if someone
     uses mqueue within that namespace, so I'm not sure it's worth it,
     especially as calling sget() allows avoidance of recursion.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index c595bed7bfcbc0aaa6891f447c6945c672f089e1..2a9a8be49f5b615076f1f1c0cc8ec9fa0c7b8e50 100644 (file)
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -18,6 +18,7 @@
 #include <linux/pagemap.h>
 #include <linux/file.h>
 #include <linux/mount.h>
+#include <linux/fs_context.h>
 #include <linux/namei.h>
 #include <linux/sysctl.h>
 #include <linux/poll.h>
@@ -42,6 +43,10 @@
 #include <net/sock.h>
 #include "util.h"
 
+struct mqueue_fs_context {
+       struct ipc_namespace    *ipc_ns;
+};
+
 #define MQUEUE_MAGIC   0x19800202
 #define DIRENT_SIZE    20
 #define FILENT_SIZE    80
@@ -87,9 +92,11 @@ struct mqueue_inode_info {
        unsigned long qsize; /* size of queue in memory (sum of all msgs) */
 };
 
+static struct file_system_type mqueue_fs_type;
 static const struct inode_operations mqueue_dir_inode_operations;
 static const struct file_operations mqueue_file_operations;
 static const struct super_operations mqueue_super_ops;
+static const struct fs_context_operations mqueue_fs_context_ops;
 static void remove_notification(struct mqueue_inode_info *info);
 
 static struct kmem_cache *mqueue_inode_cachep;
@@ -322,7 +329,7 @@ static struct inode *mqueue_get_inode(struct super_block *sb,
        return ERR_PTR(ret);
 }
 
-static int mqueue_fill_super(struct super_block *sb, void *data, int silent)
+static int mqueue_fill_super(struct super_block *sb, struct fs_context *fc)
 {
        struct inode *inode;
        struct ipc_namespace *ns = sb->s_fs_info;
@@ -343,18 +350,56 @@ static int mqueue_fill_super(struct super_block *sb, void *data, int silent)
        return 0;
 }
 
-static struct dentry *mqueue_mount(struct file_system_type *fs_type,
-                        int flags, const char *dev_name,
-                        void *data)
+static int mqueue_get_tree(struct fs_context *fc)
 {
-       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 mqueue_fs_context *ctx = fc->fs_private;
+
+       put_user_ns(fc->user_ns);
+       fc->user_ns = get_user_ns(ctx->ipc_ns->user_ns);
+       fc->s_fs_info = ctx->ipc_ns;
+       return vfs_get_super(fc, vfs_get_keyed_super, mqueue_fill_super);
+}
+
+static void mqueue_fs_context_free(struct fs_context *fc)
+{
+       struct mqueue_fs_context *ctx = fc->fs_private;
+
+       if (ctx->ipc_ns)
+               put_ipc_ns(ctx->ipc_ns);
+       kfree(ctx);
+}
+
+static int mqueue_init_fs_context(struct fs_context *fc)
+{
+       struct mqueue_fs_context *ctx;
+
+       ctx = kzalloc(sizeof(struct mqueue_fs_context), GFP_KERNEL);
+       if (!ctx)
+               return -ENOMEM;
+
+       ctx->ipc_ns = get_ipc_ns(current->nsproxy->ipc_ns);
+       fc->fs_private = ctx;
+       fc->ops = &mqueue_fs_context_ops;
+       return 0;
+}
+
+static struct vfsmount *mq_create_mount(struct ipc_namespace *ns)
+{
+       struct mqueue_fs_context *ctx;
+       struct fs_context *fc;
+       struct vfsmount *mnt;
+
+       fc = fs_context_for_mount(&mqueue_fs_type, SB_KERNMOUNT);
+       if (IS_ERR(fc))
+               return ERR_CAST(fc);
+
+       ctx = fc->fs_private;
+       put_ipc_ns(ctx->ipc_ns);
+       ctx->ipc_ns = get_ipc_ns(ns);
+
+       mnt = fc_mount(fc);
+       put_fs_context(fc);
+       return mnt;
 }
 
 static void init_once(void *foo)
@@ -1522,15 +1567,22 @@ static const struct super_operations mqueue_super_ops = {
        .statfs = simple_statfs,
 };
 
+static const struct fs_context_operations mqueue_fs_context_ops = {
+       .free           = mqueue_fs_context_free,
+       .get_tree       = mqueue_get_tree,
+};
+
 static struct file_system_type mqueue_fs_type = {
-       .name = "mqueue",
-       .mount = mqueue_mount,
-       .kill_sb = kill_litter_super,
-       .fs_flags = FS_USERNS_MOUNT,
+       .name                   = "mqueue",
+       .init_fs_context        = mqueue_init_fs_context,
+       .kill_sb                = kill_litter_super,
+       .fs_flags               = FS_USERNS_MOUNT,
 };
 
 int mq_init_ns(struct ipc_namespace *ns)
 {
+       struct vfsmount *m;
+
        ns->mq_queues_count  = 0;
        ns->mq_queues_max    = DFLT_QUEUESMAX;
        ns->mq_msg_max       = DFLT_MSGMAX;
@@ -1538,12 +1590,10 @@ int mq_init_ns(struct ipc_namespace *ns)
        ns->mq_msg_default   = DFLT_MSG;
        ns->mq_msgsize_default  = DFLT_MSGSIZE;
 
-       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;
-       }
+       m = mq_create_mount(ns);
+       if (IS_ERR(m))
+               return PTR_ERR(m);
+       ns->mq_mnt = m;
        return 0;
 }
 

diff --git a/ipc/namespace.c b/ipc/namespace.c
index 21607791d62c800a80275770ea7e7d175bfbc866..b3ca1476ca5118793c096a0244b062fbff7255b0 100644 (file)
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -42,7 +42,7 @@ static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
                goto fail;
 
        err = -ENOMEM;
-       ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
+       ns = kzalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
        if (ns == NULL)
                goto fail_dec;