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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>
This commit is contained in:
David Howells 2018-11-01 23:07:25 +00:00 committed by Al Viro
parent 66f592e2ec
commit 935c6912b1
2 changed files with 73 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

94
ipc/mqueue.c
View File

@ -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;
}
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;
}

2
ipc/namespace.c
View File

@ -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;