From 423e0ab086ad8b33626e45fa94ac7613146b7ffa Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Tue, 19 Jul 2011 09:32:38 -0700 Subject: [PATCH] VFS : mount lock scalability for internal mounts For a number of file systems that don't have a mount point (e.g. sockfs and pipefs), they are not marked as long term. Therefore in mntput_no_expire, all locks in vfs_mount lock are taken instead of just local cpu's lock to aggregate reference counts when we release reference to file objects. In fact, only local lock need to have been taken to update ref counts as these file systems are in no danger of going away until we are ready to unregister them. The attached patch marks file systems using kern_mount without mount point as long term. The contentions of vfs_mount lock is now eliminated. Before un-registering such file system, kern_unmount should be called to remove the long term flag and make the mount point ready to be freed. Signed-off-by: Tim Chen Signed-off-by: Al Viro --- drivers/mtd/mtdchar.c | 2 +- fs/anon_inodes.c | 2 +- fs/hugetlbfs/inode.c | 1 + fs/namespace.c | 21 ++++++++++++++++++++- fs/pipe.c | 2 +- include/linux/fs.h | 1 + security/selinux/selinuxfs.c | 1 + 7 files changed, 26 insertions(+), 4 deletions(-) diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c index 3f92731..f1af222 100644 --- a/drivers/mtd/mtdchar.c +++ b/drivers/mtd/mtdchar.c @@ -1192,7 +1192,7 @@ err_unregister_chdev: static void __exit cleanup_mtdchar(void) { unregister_mtd_user(&mtdchar_notifier); - mntput(mtd_inode_mnt); + kern_unmount(mtd_inode_mnt); unregister_filesystem(&mtd_inodefs_type); __unregister_chrdev(MTD_CHAR_MAJOR, 0, 1 << MINORBITS, "mtd"); } diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c index c5567cb..4d433d3 100644 --- a/fs/anon_inodes.c +++ b/fs/anon_inodes.c @@ -233,7 +233,7 @@ static int __init anon_inode_init(void) return 0; err_mntput: - mntput(anon_inode_mnt); + kern_unmount(anon_inode_mnt); err_unregister_filesystem: unregister_filesystem(&anon_inode_fs_type); err_exit: diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 7aafeb8..0b686ce 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -1030,6 +1030,7 @@ static int __init init_hugetlbfs_fs(void) static void __exit exit_hugetlbfs_fs(void) { kmem_cache_destroy(hugetlbfs_inode_cachep); + kern_unmount(hugetlbfs_vfsmount); unregister_filesystem(&hugetlbfs_fs_type); bdi_destroy(&hugetlbfs_backing_dev_info); } diff --git a/fs/namespace.c b/fs/namespace.c index cda50fe..22bfe82 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2721,6 +2721,25 @@ EXPORT_SYMBOL(put_mnt_ns); struct vfsmount *kern_mount_data(struct file_system_type *type, void *data) { - return vfs_kern_mount(type, MS_KERNMOUNT, type->name, data); + struct vfsmount *mnt; + mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data); + if (!IS_ERR(mnt)) { + /* + * it is a longterm mount, don't release mnt until + * we unmount before file sys is unregistered + */ + mnt_make_longterm(mnt); + } + return mnt; } EXPORT_SYMBOL_GPL(kern_mount_data); + +void kern_unmount(struct vfsmount *mnt) +{ + /* release long term mount so mount point can be released */ + if (!IS_ERR_OR_NULL(mnt)) { + mnt_make_shortterm(mnt); + mntput(mnt); + } +} +EXPORT_SYMBOL(kern_unmount); diff --git a/fs/pipe.c b/fs/pipe.c index da42f7d..1b7f9af 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -1291,8 +1291,8 @@ static int __init init_pipe_fs(void) static void __exit exit_pipe_fs(void) { + kern_unmount(pipe_mnt); unregister_filesystem(&pipe_fs_type); - mntput(pipe_mnt); } fs_initcall(init_pipe_fs); diff --git a/include/linux/fs.h b/include/linux/fs.h index b224dc4..7a757a4 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1885,6 +1885,7 @@ extern int register_filesystem(struct file_system_type *); extern int unregister_filesystem(struct file_system_type *); extern struct vfsmount *kern_mount_data(struct file_system_type *, void *data); #define kern_mount(type) kern_mount_data(type, NULL) +extern void kern_unmount(struct vfsmount *mnt); extern int may_umount_tree(struct vfsmount *); extern int may_umount(struct vfsmount *); extern long do_mount(char *, char *, char *, unsigned long, void *); diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c index 3545934..de7900e 100644 --- a/security/selinux/selinuxfs.c +++ b/security/selinux/selinuxfs.c @@ -1984,6 +1984,7 @@ __initcall(init_sel_fs); void exit_sel_fs(void) { kobject_put(selinuxfs_kobj); + kern_unmount(selinuxfs_mount); unregister_filesystem(&sel_fs_type); } #endif -- 2.7.4