From 4b93dc9b1c684d0587fe44d36bbfdf45bd3bea9d Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 28 Nov 2013 14:54:43 -0500 Subject: sysfs, kernfs: prepare mount path for kernfs We're in the process of separating out core sysfs functionality into kernfs which will deal with sysfs_dirents directly. This patch rearranges mount path so that the kernfs and sysfs parts are separate. * As sysfs_super_info won't be visible outside kernfs proper, kernfs_super_ns() is added to allow kernfs users to access a super_block's namespace tag. * Generic mount operation is separated out into kernfs_mount_ns(). sysfs_mount() now just performs sysfs-specific permission check, acquires namespace tag, and invokes kernfs_mount_ns(). * Generic superblock release is separated out into kernfs_kill_sb() which can be used directly as file_system_type->kill_sb(). As sysfs needs to put the namespace tag, sysfs_kill_sb() wraps kernfs_kill_sb() with ns tag put. * sysfs_dir_cachep init and sysfs_inode_init() are separated out into kernfs_init(). kernfs_init() uses only small amount of memory and trying to handle and propagate kernfs_init() failure doesn't make much sense. Use SLAB_PANIC for sysfs_dir_cachep and make sysfs_inode_init() panic on failure. After this change, kernfs_init() should be called before sysfs_init(), fs/namespace.c::mnt_init() modified accordingly. Signed-off-by: Tejun Heo Cc: linux-fsdevel@vger.kernel.org Cc: Christoph Hellwig Signed-off-by: Greg Kroah-Hartman --- fs/sysfs/mount.c | 104 ++++++++++++++++++++++++++++++++++++++----------------- 1 file changed, 72 insertions(+), 32 deletions(-) (limited to 'fs/sysfs') diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c index f143b203a7e6..5384732700ba 100644 --- a/fs/sysfs/mount.c +++ b/fs/sysfs/mount.c @@ -86,18 +86,24 @@ static int sysfs_set_super(struct super_block *sb, void *data) return error; } -static void free_sysfs_super_info(struct sysfs_super_info *info) +/** + * kernfs_super_ns - determine the namespace tag of a kernfs super_block + * @sb: super_block of interest + * + * Return the namespace tag associated with kernfs super_block @sb. + */ +const void *kernfs_super_ns(struct super_block *sb) { - kobj_ns_drop(KOBJ_NS_TYPE_NET, (void *)info->ns); - kfree(info); + struct sysfs_super_info *info = sysfs_info(sb); + + return info->ns; } static struct dentry *sysfs_mount(struct file_system_type *fs_type, int flags, const char *dev_name, void *data) { - struct sysfs_super_info *info; - struct super_block *sb; - int error; + struct dentry *root; + void *ns; if (!(flags & MS_KERNMOUNT)) { if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type)) @@ -107,16 +113,44 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type, return ERR_PTR(-EPERM); } + ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET); + root = kernfs_mount_ns(fs_type, flags, sysfs_root, ns); + if (IS_ERR(root)) + kobj_ns_drop(KOBJ_NS_TYPE_NET, ns); + return root; +} + +/** + * kernfs_mount_ns - kernfs mount helper + * @fs_type: file_system_type of the fs being mounted + * @flags: mount flags specified for the mount + * @root: kernfs_root of the hierarchy being mounted + * @ns: optional namespace tag of the mount + * + * This is to be called from each kernfs user's file_system_type->mount() + * implementation, which should pass through the specified @fs_type and + * @flags, and specify the hierarchy and namespace tag to mount via @root + * and @ns, respectively. + * + * The return value can be passed to the vfs layer verbatim. + */ +struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags, + struct kernfs_root *root, const void *ns) +{ + struct super_block *sb; + struct sysfs_super_info *info; + int error; + info = kzalloc(sizeof(*info), GFP_KERNEL); if (!info) return ERR_PTR(-ENOMEM); - info->root = sysfs_root; - info->ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET); + info->root = root; + info->ns = ns; sb = sget(fs_type, sysfs_test_super, sysfs_set_super, flags, info); if (IS_ERR(sb) || sb->s_fs_info != info) - free_sysfs_super_info(info); + kfree(info); if (IS_ERR(sb)) return ERR_CAST(sb); if (!sb->s_root) { @@ -132,6 +166,20 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type, } static void sysfs_kill_sb(struct super_block *sb) +{ + kernfs_kill_sb(sb); + kobj_ns_drop(KOBJ_NS_TYPE_NET, (void *)kernfs_super_ns(sb)); +} + +/** + * kernfs_kill_sb - kill_sb for kernfs + * @sb: super_block being killed + * + * This can be used directly for file_system_type->kill_sb(). If a kernfs + * user needs extra cleanup, it can implement its own kill_sb() and call + * this function at the end. + */ +void kernfs_kill_sb(struct super_block *sb) { struct sysfs_super_info *info = sysfs_info(sb); struct sysfs_dirent *root_sd = sb->s_root->d_fsdata; @@ -141,7 +189,7 @@ static void sysfs_kill_sb(struct super_block *sb) * so we can't find it, before freeing sysfs_super_info. */ kill_anon_super(sb); - free_sysfs_super_info(info); + kfree(info); kernfs_put(root_sd); } @@ -152,37 +200,29 @@ static struct file_system_type sysfs_fs_type = { .fs_flags = FS_USERNS_MOUNT, }; -int __init sysfs_init(void) +void __init kernfs_init(void) { - int err; - sysfs_dir_cachep = kmem_cache_create("sysfs_dir_cache", sizeof(struct sysfs_dirent), - 0, 0, NULL); - if (!sysfs_dir_cachep) - return -ENOMEM; + 0, SLAB_PANIC, NULL); + sysfs_inode_init(); +} - err = sysfs_inode_init(); - if (err) - goto out_err; +int __init sysfs_init(void) +{ + int err; sysfs_root = kernfs_create_root(NULL); - if (IS_ERR(sysfs_root)) { - err = PTR_ERR(sysfs_root); - goto out_err; - } + if (IS_ERR(sysfs_root)) + return PTR_ERR(sysfs_root); + sysfs_root_sd = sysfs_root->sd; err = register_filesystem(&sysfs_fs_type); - if (err) - goto out_destroy_root; + if (err) { + kernfs_destroy_root(sysfs_root); + return err; + } return 0; - -out_destroy_root: - kernfs_destroy_root(sysfs_root); -out_err: - kmem_cache_destroy(sysfs_dir_cachep); - sysfs_dir_cachep = NULL; - return err; } -- cgit v1.2.3