Return-Path: Received: from mx3-rdu2.redhat.com ([66.187.233.73]:60548 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751449AbeDSNch (ORCPT ); Thu, 19 Apr 2018 09:32:37 -0400 Subject: [PATCH 13/24] ipc: Convert mqueue fs to fs_context [ver #7] From: David Howells To: viro@zeniv.linux.org.uk Cc: linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, dhowells@redhat.com, linux-security-module@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-afs@lists.infradead.org Date: Thu, 19 Apr 2018 14:32:35 +0100 Message-ID: <152414475508.23902.7607267381447716752.stgit@warthog.procyon.org.uk> In-Reply-To: <152414466005.23902.12967974041384198114.stgit@warthog.procyon.org.uk> References: <152414466005.23902.12967974041384198114.stgit@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Sender: linux-nfs-owner@vger.kernel.org List-ID: 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 --- ipc/mqueue.c | 116 +++++++++++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 94 insertions(+), 22 deletions(-) diff --git a/ipc/mqueue.c b/ipc/mqueue.c index 910c3c7532e6..2f2e7d73b13d 100644 --- a/ipc/mqueue.c +++ b/ipc/mqueue.c @@ -18,6 +18,7 @@ #include #include #include +#include #include #include #include @@ -42,6 +43,11 @@ #include #include "util.h" +struct mqueue_fs_context { + struct fs_context fc; + struct ipc_namespace *ipc_ns; +}; + #define MQUEUE_MAGIC 0x19800202 #define DIRENT_SIZE 20 #define FILENT_SIZE 80 @@ -87,9 +93,11 @@ 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 +330,7 @@ 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, size_t data_size, 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; @@ -343,19 +351,77 @@ static int mqueue_fill_super(struct super_block *sb, void *data, size_t data_siz return 0; } -static struct dentry *mqueue_mount(struct file_system_type *fs_type, - int flags, const char *dev_name, - void *data, size_t data_size) +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 = container_of(fc, struct mqueue_fs_context, fc); + + /* As a shortcut, if the namespace already has a superblock created, + * use the root from that directly rather than invoking sget() again. + */ + spin_lock(&mq_lock); + if (ctx->ipc_ns->mq_mnt) { + fc->root = dget(ctx->ipc_ns->mq_mnt->mnt_sb->s_root); + atomic_inc(&fc->root->d_sb->s_active); + } + spin_unlock(&mq_lock); + if (fc->root) { + down_write(&fc->root->d_sb->s_umount); + return 0; } - return mount_ns(fs_type, flags, data, data_size, ns, ns->user_ns, - mqueue_fill_super); + + ctx->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 = container_of(fc, struct mqueue_fs_context, fc); + + if (ctx->ipc_ns) + put_ipc_ns(ctx->ipc_ns); +} + +static int mqueue_init_fs_context(struct fs_context *fc, struct super_block *src_sb) +{ + struct mqueue_fs_context *ctx = container_of(fc, struct mqueue_fs_context, fc); + + ctx->ipc_ns = get_ipc_ns(current->nsproxy->ipc_ns); + 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; + int ret; + + fc = vfs_new_fs_context(&mqueue_fs_type, NULL, 0, + FS_CONTEXT_FOR_KERNEL_MOUNT); + if (IS_ERR(fc)) + return ERR_CAST(fc); + + ctx = container_of(fc, struct mqueue_fs_context, fc); + put_ipc_ns(ctx->ipc_ns); + ctx->ipc_ns = get_ipc_ns(ns); + + ret = vfs_get_tree(fc); + if (ret < 0) + goto err_fc; + + mnt = vfs_create_mount(fc); + if (IS_ERR(mnt)) { + ret = PTR_ERR(mnt); + goto err_fc; + } + + put_fs_context(fc); + return mnt; + +err_fc: + put_fs_context(fc); + return ERR_PTR(ret); } static void init_once(void *foo) @@ -1521,15 +1587,23 @@ 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", + .fs_context_size = sizeof(struct mqueue_fs_context), + .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; @@ -1537,12 +1611,10 @@ 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, 0); - if (IS_ERR(ns->mq_mnt)) { - int err = PTR_ERR(ns->mq_mnt); - ns->mq_mnt = NULL; - return err; - } + m = mq_create_mount(&init_ipc_ns); + if (IS_ERR(m)) + return PTR_ERR(ns->mq_mnt); + ns->mq_mnt = m; return 0; }