takes vfsmount and relative path, does lookup within that vfsmount (possibly triggering automounts) and returns the result as root of subtree suitable for return by ->mount() (i.e. a reference to dentry and an active reference to its superblock grabbed, superblock locked exclusive). btrfs and nfs switched to it instead of open-coding the sucker.
Unified · Split
| @@ -825,13 +825,9 @@ static char *setup_root_args(char *args) · 824 unmodified lines | |||
| 825 | static struct dentry *mount_subvol(const char *subvol_name, int flags, | 825 | static struct dentry *mount_subvol(const char *subvol_name, int flags, |
| 826 | const char *device_name, char *data) | 826 | const char *device_name, char *data) |
| 827 | { | 827 | { |
| 828 | struct super_block *s; | ||
| 829 | struct dentry *root; | 828 | struct dentry *root; |
| 830 | struct vfsmount *mnt; | 829 | struct vfsmount *mnt; |
| 831 | struct mnt_namespace *ns_private; | ||
| 832 | char *newargs; | 830 | char *newargs; |
| 833 | struct path path; | ||
| 834 | int error; | ||
| 835 | 831 | ||
| 836 | newargs = setup_root_args(data); | 832 | newargs = setup_root_args(data); |
| 837 | if (!newargs) | 833 | if (!newargs) |
| @@ -842,36 +838,17 @@ static struct dentry *mount_subvol(const char *subvol_name, int flags, · 4 unmodified lines | |||
| 842 | if (IS_ERR(mnt)) | 838 | if (IS_ERR(mnt)) |
| 843 | return ERR_CAST(mnt); | 839 | return ERR_CAST(mnt); |
| 844 | 840 | ||
| 845 | ns_private = create_mnt_ns(mnt); | 841 | root = mount_subtree(mnt, subvol_name); |
| 846 | if (IS_ERR(ns_private)) | ||
| 847 | return ERR_CAST(ns_private); | ||
| 848 | |||
| 849 | /* | ||
| 850 | * This will trigger the automount of the subvol so we can just | ||
| 851 | * drop the mnt we have here and return the dentry that we | ||
| 852 | * found. | ||
| 853 | */ | ||
| 854 | error = vfs_path_lookup(mnt->mnt_root, mnt, subvol_name, | ||
| 855 | LOOKUP_FOLLOW, &path); | ||
| 856 | put_mnt_ns(ns_private); | ||
| 857 | if (error) | ||
| 858 | return ERR_PTR(error); | ||
| 859 | 842 | ||
| 860 | if (!is_subvolume_inode(path.dentry->d_inode)) { | 843 | if (!IS_ERR(root) && !is_subvolume_inode(root->d_inode)) { |
| 861 | path_put(&path); | 844 | struct super_block *s = root->d_sb; |
| 862 | error = -EINVAL; | 845 | dput(root); |
| 846 | root = ERR_PTR(-EINVAL); | ||
| 847 | deactivate_locked_super(s); | ||
| 863 | printk(KERN_ERR "btrfs: '%s' is not a valid subvolume\n", | 848 | printk(KERN_ERR "btrfs: '%s' is not a valid subvolume\n", |
| 864 | subvol_name); | 849 | subvol_name); |
| 865 | return ERR_PTR(-EINVAL); | ||
| 866 | } | 850 | } |
| 867 | 851 | ||
| 868 | /* Get a ref to the sb and the dentry we found and return it */ | ||
| 869 | s = path.mnt->mnt_sb; | ||
| 870 | atomic_inc(&s->s_active); | ||
| 871 | root = dget(path.dentry); | ||
| 872 | path_put(&path); | ||
| 873 | down_write(&s->s_umount); | ||
| 874 | |||
| 875 | return root; | 852 | return root; |
| 876 | } | 853 | } |
| 877 | 854 | ||
| @@ -2490,6 +2490,34 @@ struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt) · 2489 unmodified lines | |||
| 2490 | } | 2490 | } |
| 2491 | EXPORT_SYMBOL(create_mnt_ns); | 2491 | EXPORT_SYMBOL(create_mnt_ns); |
| 2492 | 2492 | ||
| 2493 | struct dentry *mount_subtree(struct vfsmount *mnt, const char *name) | ||
| 2494 | { | ||
| 2495 | struct mnt_namespace *ns; | ||
| 2496 | struct path path; | ||
| 2497 | int err; | ||
| 2498 | |||
| 2499 | ns = create_mnt_ns(mnt); | ||
| 2500 | if (IS_ERR(ns)) | ||
| 2501 | return ERR_CAST(ns); | ||
| 2502 | |||
| 2503 | err = vfs_path_lookup(mnt->mnt_root, mnt, | ||
| 2504 | name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path); | ||
| 2505 | |||
| 2506 | put_mnt_ns(ns); | ||
| 2507 | |||
| 2508 | if (err) | ||
| 2509 | return ERR_PTR(err); | ||
| 2510 | |||
| 2511 | /* trade a vfsmount reference for active sb one */ | ||
| 2512 | atomic_inc(&path.mnt->mnt_sb->s_active); | ||
| 2513 | mntput(path.mnt); | ||
| 2514 | /* lock the sucker */ | ||
| 2515 | down_write(&path.mnt->mnt_sb->s_umount); | ||
| 2516 | /* ... and return the root of (sub)tree on it */ | ||
| 2517 | return path.dentry; | ||
| 2518 | } | ||
| 2519 | EXPORT_SYMBOL(mount_subtree); | ||
| 2520 | |||
| 2493 | SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, | 2521 | SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, |
| 2494 | char __user *, type, unsigned long, flags, void __user *, data) | 2522 | char __user *, type, unsigned long, flags, void __user *, data) |
| 2495 | { | 2523 | { |
| @@ -2787,35 +2787,17 @@ static void nfs_referral_loop_unprotect(void) · 2786 unmodified lines | |||
| 2787 | static struct dentry *nfs_follow_remote_path(struct vfsmount *root_mnt, | 2787 | static struct dentry *nfs_follow_remote_path(struct vfsmount *root_mnt, |
| 2788 | const char *export_path) | 2788 | const char *export_path) |
| 2789 | { | 2789 | { |
| 2790 | struct mnt_namespace *ns_private; | ||
| 2791 | struct super_block *s; | ||
| 2792 | struct dentry *dentry; | 2790 | struct dentry *dentry; |
| 2793 | struct path path; | 2791 | int ret = nfs_referral_loop_protect(); |
| 2794 | int ret; | ||
| 2795 | 2792 | ||
| 2796 | ns_private = create_mnt_ns(root_mnt); | 2793 | if (ret) { |
| 2797 | if (IS_ERR(ns_private)) | 2794 | mntput(root_mnt); |
| 2798 | return ERR_CAST(ns_private); | ||
| 2799 | |||
| 2800 | ret = nfs_referral_loop_protect(); | ||
| 2801 | if (ret == 0) { | ||
| 2802 | ret = vfs_path_lookup(root_mnt->mnt_root, root_mnt, | ||
| 2803 | export_path, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, | ||
| 2804 | &path); | ||
| 2805 | nfs_referral_loop_unprotect(); | ||
| 2806 | } | ||
| 2807 | |||
| 2808 | put_mnt_ns(ns_private); | ||
| 2809 | |||
| 2810 | if (ret != 0) | ||
| 2811 | return ERR_PTR(ret); | 2795 | return ERR_PTR(ret); |
| 2796 | } | ||
| 2812 | 2797 | ||
| 2813 | s = path.mnt->mnt_sb; | 2798 | dentry = mount_subtree(root_mnt, export_path); |
| 2814 | atomic_inc(&s->s_active); | 2799 | nfs_referral_loop_unprotect(); |
| 2815 | dentry = dget(path.dentry); | ||
| 2816 | 2800 | ||
| 2817 | path_put(&path); | ||
| 2818 | down_write(&s->s_umount); | ||
| 2819 | return dentry; | 2801 | return dentry; |
| 2820 | } | 2802 | } |
| 2821 | 2803 | ||
| @@ -1886,6 +1886,7 @@ extern struct dentry *mount_single(struct file_system_type *fs_type, · 1885 unmodified lines | |||
| 1886 | extern struct dentry *mount_nodev(struct file_system_type *fs_type, | 1886 | extern struct dentry *mount_nodev(struct file_system_type *fs_type, |
| 1887 | int flags, void *data, | 1887 | int flags, void *data, |
| 1888 | int (*fill_super)(struct super_block *, void *, int)); | 1888 | int (*fill_super)(struct super_block *, void *, int)); |
| 1889 | extern struct dentry *mount_subtree(struct vfsmount *mnt, const char *path); | ||
| 1889 | void generic_shutdown_super(struct super_block *sb); | 1890 | void generic_shutdown_super(struct super_block *sb); |
| 1890 | void kill_block_super(struct super_block *sb); | 1891 | void kill_block_super(struct super_block *sb); |
| 1891 | void kill_anon_super(struct super_block *sb); | 1892 | void kill_anon_super(struct super_block *sb); |