Commit 935c6912 authored by David Howells's avatar David Howells Committed by Al Viro
Browse files

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: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 66f592e2

ipc/mqueue.c

+72 −22
Original line number Diff line number Diff line
@@ -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 @@ err: 
	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;

	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);

}

	return mount_ns(fs_type, flags, data, ns, ns->user_ns, 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,

	.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;

}

ipc/namespace.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

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