diff options
author | David Howells <dhowells@redhat.com> | 2018-11-01 23:07:25 +0000 |
---|---|---|
committer | Al Viro <viro@zeniv.linux.org.uk> | 2019-02-28 03:29:29 -0500 |
commit | 935c6912b198f60a812b7dada21027b5aac7c461 (patch) | |
tree | b948022b6e597e4e108d773fd9ceeea2985965d6 /ipc | |
parent | 66f592e2ece0389c018d74d1bbb2d0b9738cfe48 (diff) | |
download | lwn-935c6912b198f60a812b7dada21027b5aac7c461.tar.gz lwn-935c6912b198f60a812b7dada21027b5aac7c461.zip |
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>
Diffstat (limited to 'ipc')
-rw-r--r-- | ipc/mqueue.c | 94 | ||||
-rw-r--r-- | ipc/namespace.c | 2 |
2 files changed, 73 insertions, 23 deletions
diff --git a/ipc/mqueue.c b/ipc/mqueue.c index c595bed7bfcb..2a9a8be49f5b 100644 --- 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 @@ 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; } diff --git a/ipc/namespace.c b/ipc/namespace.c index 21607791d62c..b3ca1476ca51 100644 --- 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; |