diff options
Diffstat (limited to 'fs/namespace.c')
| -rw-r--r-- | fs/namespace.c | 242 |
1 files changed, 199 insertions, 43 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index 03b82350f02..3ddfd9046c4 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -138,6 +138,64 @@ void mnt_release_group_id(struct vfsmount *mnt) mnt->mnt_group_id = 0; } +/* + * vfsmount lock must be held for read + */ +static inline void mnt_add_count(struct vfsmount *mnt, int n) +{ +#ifdef CONFIG_SMP + this_cpu_add(mnt->mnt_pcp->mnt_count, n); +#else + preempt_disable(); + mnt->mnt_count += n; + preempt_enable(); +#endif +} + +static inline void mnt_set_count(struct vfsmount *mnt, int n) +{ +#ifdef CONFIG_SMP + this_cpu_write(mnt->mnt_pcp->mnt_count, n); +#else + mnt->mnt_count = n; +#endif +} + +/* + * vfsmount lock must be held for read + */ +static inline void mnt_inc_count(struct vfsmount *mnt) +{ + mnt_add_count(mnt, 1); +} + +/* + * vfsmount lock must be held for read + */ +static inline void mnt_dec_count(struct vfsmount *mnt) +{ + mnt_add_count(mnt, -1); +} + +/* + * vfsmount lock must be held for write + */ +unsigned int mnt_get_count(struct vfsmount *mnt) +{ +#ifdef CONFIG_SMP + unsigned int count = atomic_read(&mnt->mnt_longrefs); + int cpu; + + for_each_possible_cpu(cpu) { + count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count; + } + + return count; +#else + return mnt->mnt_count; +#endif +} + struct vfsmount *alloc_vfsmnt(const char *name) { struct vfsmount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); @@ -154,7 +212,17 @@ struct vfsmount *alloc_vfsmnt(const char *name) goto out_free_id; } - atomic_set(&mnt->mnt_count, 1); +#ifdef CONFIG_SMP + mnt->mnt_pcp = alloc_percpu(struct mnt_pcp); + if (!mnt->mnt_pcp) + goto out_free_devname; + + atomic_set(&mnt->mnt_longrefs, 1); +#else + mnt->mnt_count = 1; + mnt->mnt_writers = 0; +#endif + INIT_LIST_HEAD(&mnt->mnt_hash); INIT_LIST_HEAD(&mnt->mnt_child); INIT_LIST_HEAD(&mnt->mnt_mounts); @@ -166,13 +234,6 @@ struct vfsmount *alloc_vfsmnt(const char *name) #ifdef CONFIG_FSNOTIFY INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks); #endif -#ifdef CONFIG_SMP - mnt->mnt_writers = alloc_percpu(int); - if (!mnt->mnt_writers) - goto out_free_devname; -#else - mnt->mnt_writers = 0; -#endif } return mnt; @@ -219,7 +280,7 @@ EXPORT_SYMBOL_GPL(__mnt_is_readonly); static inline void mnt_inc_writers(struct vfsmount *mnt) { #ifdef CONFIG_SMP - (*per_cpu_ptr(mnt->mnt_writers, smp_processor_id()))++; + this_cpu_inc(mnt->mnt_pcp->mnt_writers); #else mnt->mnt_writers++; #endif @@ -228,7 +289,7 @@ static inline void mnt_inc_writers(struct vfsmount *mnt) static inline void mnt_dec_writers(struct vfsmount *mnt) { #ifdef CONFIG_SMP - (*per_cpu_ptr(mnt->mnt_writers, smp_processor_id()))--; + this_cpu_dec(mnt->mnt_pcp->mnt_writers); #else mnt->mnt_writers--; #endif @@ -241,7 +302,7 @@ static unsigned int mnt_get_writers(struct vfsmount *mnt) int cpu; for_each_possible_cpu(cpu) { - count += *per_cpu_ptr(mnt->mnt_writers, cpu); + count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers; } return count; @@ -418,7 +479,7 @@ void free_vfsmnt(struct vfsmount *mnt) kfree(mnt->mnt_devname); mnt_free_id(mnt); #ifdef CONFIG_SMP - free_percpu(mnt->mnt_writers); + free_percpu(mnt->mnt_pcp); #endif kmem_cache_free(mnt_cache, mnt); } @@ -652,9 +713,10 @@ static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root, return NULL; } -static inline void __mntput(struct vfsmount *mnt) +static inline void mntfree(struct vfsmount *mnt) { struct super_block *sb = mnt->mnt_sb; + /* * This probably indicates that somebody messed * up a mnt_want/drop_write() pair. If this @@ -662,8 +724,8 @@ static inline void __mntput(struct vfsmount *mnt) * to make r/w->r/o transitions. */ /* - * atomic_dec_and_lock() used to deal with ->mnt_count decrements - * provides barriers, so mnt_get_writers() below is safe. AV + * The locking used to deal with mnt_count decrement provides barriers, + * so mnt_get_writers() below is safe. */ WARN_ON(mnt_get_writers(mnt)); fsnotify_vfsmount_delete(mnt); @@ -672,28 +734,113 @@ static inline void __mntput(struct vfsmount *mnt) deactivate_super(sb); } -void mntput_no_expire(struct vfsmount *mnt) -{ -repeat: - if (atomic_add_unless(&mnt->mnt_count, -1, 1)) - return; +#ifdef CONFIG_SMP +static inline void __mntput(struct vfsmount *mnt, int longrefs) +{ + if (!longrefs) { +put_again: + br_read_lock(vfsmount_lock); + if (likely(atomic_read(&mnt->mnt_longrefs))) { + mnt_dec_count(mnt); + br_read_unlock(vfsmount_lock); + return; + } + br_read_unlock(vfsmount_lock); + } else { + BUG_ON(!atomic_read(&mnt->mnt_longrefs)); + if (atomic_add_unless(&mnt->mnt_longrefs, -1, 1)) + return; + } + br_write_lock(vfsmount_lock); - if (!atomic_dec_and_test(&mnt->mnt_count)) { + if (!longrefs) + mnt_dec_count(mnt); + else + atomic_dec(&mnt->mnt_longrefs); + if (mnt_get_count(mnt)) { br_write_unlock(vfsmount_lock); return; } - if (likely(!mnt->mnt_pinned)) { + if (unlikely(mnt->mnt_pinned)) { + mnt_add_count(mnt, mnt->mnt_pinned + 1); + mnt->mnt_pinned = 0; br_write_unlock(vfsmount_lock); - __mntput(mnt); + acct_auto_close_mnt(mnt); + goto put_again; + } + br_write_unlock(vfsmount_lock); + mntfree(mnt); +} +#else +static inline void __mntput(struct vfsmount *mnt, int longrefs) +{ +put_again: + mnt_dec_count(mnt); + if (likely(mnt_get_count(mnt))) return; + br_write_lock(vfsmount_lock); + if (unlikely(mnt->mnt_pinned)) { + mnt_add_count(mnt, mnt->mnt_pinned + 1); + mnt->mnt_pinned = 0; + br_write_unlock(vfsmount_lock); + acct_auto_close_mnt(mnt); + goto put_again; } - atomic_add(mnt->mnt_pinned + 1, &mnt->mnt_count); - mnt->mnt_pinned = 0; br_write_unlock(vfsmount_lock); - acct_auto_close_mnt(mnt); - goto repeat; + mntfree(mnt); +} +#endif + +static void mntput_no_expire(struct vfsmount *mnt) +{ + __mntput(mnt, 0); +} + +void mntput(struct vfsmount *mnt) +{ + if (mnt) { + /* avoid cacheline pingpong, hope gcc doesn't get "smart" */ + if (unlikely(mnt->mnt_expiry_mark)) + mnt->mnt_expiry_mark = 0; + __mntput(mnt, 0); + } +} +EXPORT_SYMBOL(mntput); + +struct vfsmount *mntget(struct vfsmount *mnt) +{ + if (mnt) + mnt_inc_count(mnt); + return mnt; +} +EXPORT_SYMBOL(mntget); + +void mntput_long(struct vfsmount *mnt) +{ +#ifdef CONFIG_SMP + if (mnt) { + /* avoid cacheline pingpong, hope gcc doesn't get "smart" */ + if (unlikely(mnt->mnt_expiry_mark)) + mnt->mnt_expiry_mark = 0; + __mntput(mnt, 1); + } +#else + mntput(mnt); +#endif } -EXPORT_SYMBOL(mntput_no_expire); +EXPORT_SYMBOL(mntput_long); + +struct vfsmount *mntget_long(struct vfsmount *mnt) +{ +#ifdef CONFIG_SMP + if (mnt) + atomic_inc(&mnt->mnt_longrefs); + return mnt; +#else + return mntget(mnt); +#endif +} +EXPORT_SYMBOL(mntget_long); void mnt_pin(struct vfsmount *mnt) { @@ -701,19 +848,17 @@ void mnt_pin(struct vfsmount *mnt) mnt->mnt_pinned++; br_write_unlock(vfsmount_lock); } - EXPORT_SYMBOL(mnt_pin); void mnt_unpin(struct vfsmount *mnt) { br_write_lock(vfsmount_lock); if (mnt->mnt_pinned) { - atomic_inc(&mnt->mnt_count); + mnt_inc_count(mnt); mnt->mnt_pinned--; } br_write_unlock(vfsmount_lock); } - EXPORT_SYMBOL(mnt_unpin); static inline void mangle(struct seq_file *m, const char *s) @@ -1008,12 +1153,13 @@ int may_umount_tree(struct vfsmount *mnt) int minimum_refs = 0; struct vfsmount *p; - br_read_lock(vfsmount_lock); + /* write lock needed for mnt_get_count */ + br_write_lock(vfsmount_lock); for (p = mnt; p; p = next_mnt(p, mnt)) { - actual_refs += atomic_read(&p->mnt_count); + actual_refs += mnt_get_count(p); minimum_refs += 2; } - br_read_unlock(vfsmount_lock); + br_write_unlock(vfsmount_lock); if (actual_refs > minimum_refs) return 0; @@ -1040,10 +1186,10 @@ int may_umount(struct vfsmount *mnt) { int ret = 1; down_read(&namespace_sem); - br_read_lock(vfsmount_lock); + br_write_lock(vfsmount_lock); if (propagate_mount_busy(mnt, 2)) ret = 0; - br_read_unlock(vfsmount_lock); + br_write_unlock(vfsmount_lock); up_read(&namespace_sem); return ret; } @@ -1070,7 +1216,7 @@ void release_mounts(struct list_head *head) dput(dentry); mntput(m); } - mntput(mnt); + mntput_long(mnt); } } @@ -1125,8 +1271,16 @@ static int do_umount(struct vfsmount *mnt, int flags) flags & (MNT_FORCE | MNT_DETACH)) return -EINVAL; - if (atomic_read(&mnt->mnt_count) != 2) + /* + * probably don't strictly need the lock here if we examined + * all race cases, but it's a slowpath. + */ + br_write_lock(vfsmount_lock); + if (mnt_get_count(mnt) != 2) { + br_write_lock(vfsmount_lock); return -EBUSY; + } + br_write_unlock(vfsmount_lock); if (!xchg(&mnt->mnt_expiry_mark, 1)) return -EAGAIN; @@ -1815,7 +1969,7 @@ int do_add_mount(struct vfsmount *newmnt, struct path *path, unlock: up_write(&namespace_sem); - mntput(newmnt); + mntput_long(newmnt); return err; } @@ -2148,11 +2302,11 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns, if (fs) { if (p == fs->root.mnt) { rootmnt = p; - fs->root.mnt = mntget(q); + fs->root.mnt = mntget_long(q); } if (p == fs->pwd.mnt) { pwdmnt = p; - fs->pwd.mnt = mntget(q); + fs->pwd.mnt = mntget_long(q); } } p = next_mnt(p, mnt_ns->root); @@ -2161,9 +2315,9 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns, up_write(&namespace_sem); if (rootmnt) - mntput(rootmnt); + mntput_long(rootmnt); if (pwdmnt) - mntput(pwdmnt); + mntput_long(pwdmnt); return new_ns; } @@ -2350,6 +2504,7 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, touch_mnt_namespace(current->nsproxy->mnt_ns); br_write_unlock(vfsmount_lock); chroot_fs_refs(&root, &new); + error = 0; path_put(&root_parent); path_put(&parent_path); @@ -2376,6 +2531,7 @@ static void __init init_mount_tree(void) mnt = do_kern_mount("rootfs", 0, "rootfs", NULL); if (IS_ERR(mnt)) panic("Can't create rootfs"); + ns = create_mnt_ns(mnt); if (IS_ERR(ns)) panic("Can't allocate initial namespace"); |