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Subject[patch 04/33] fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock.
---
fs/dcache.c | 4
fs/namei.c | 13 +-
fs/namespace.c | 201 ++++++++++++++++++++++++++++++---------------
fs/pnode.c | 4
fs/proc/base.c | 4
include/linux/mount.h | 6 +
kernel/audit_tree.c | 6 -
security/tomoyo/realpath.c | 4
8 files changed, 161 insertions(+), 81 deletions(-)
Index: linux-2.6/fs/dcache.c
===================================================================
--- linux-2.6.orig/fs/dcache.c
+++ linux-2.6/fs/dcache.c
@@ -1908,7 +1908,7 @@ char *__d_path(const struct path *path,
char *end = buffer + buflen;
char *retval;

- spin_lock(&vfsmount_lock);
+ vfsmount_read_lock();
prepend(&end, &buflen, "\0", 1);
if (d_unlinked(dentry) &&
(prepend(&end, &buflen, " (deleted)", 10) != 0))
@@ -1944,7 +1944,7 @@ char *__d_path(const struct path *path,
}

out:
- spin_unlock(&vfsmount_lock);
+ vfsmount_read_unlock();
return retval;

global_root:
Index: linux-2.6/fs/namei.c
===================================================================
--- linux-2.6.orig/fs/namei.c
+++ linux-2.6/fs/namei.c
@@ -679,15 +679,16 @@ int follow_up(struct path *path)
{
struct vfsmount *parent;
struct dentry *mountpoint;
- spin_lock(&vfsmount_lock);
+
+ vfsmount_read_unlock();
parent = path->mnt->mnt_parent;
if (parent == path->mnt) {
- spin_unlock(&vfsmount_lock);
+ vfsmount_read_unlock();
return 0;
}
mntget(parent);
mountpoint = dget(path->mnt->mnt_mountpoint);
- spin_unlock(&vfsmount_lock);
+ vfsmount_read_unlock();
dput(path->dentry);
path->dentry = mountpoint;
mntput(path->mnt);
@@ -766,15 +767,15 @@ static __always_inline void follow_dotdo
break;
}
spin_unlock(&dcache_lock);
- spin_lock(&vfsmount_lock);
+ vfsmount_read_lock();
parent = nd->path.mnt->mnt_parent;
if (parent == nd->path.mnt) {
- spin_unlock(&vfsmount_lock);
+ vfsmount_read_unlock();
break;
}
mntget(parent);
nd->path.dentry = dget(nd->path.mnt->mnt_mountpoint);
- spin_unlock(&vfsmount_lock);
+ vfsmount_read_unlock();
dput(old);
mntput(nd->path.mnt);
nd->path.mnt = parent;
Index: linux-2.6/fs/namespace.c
===================================================================
--- linux-2.6.orig/fs/namespace.c
+++ linux-2.6/fs/namespace.c
@@ -11,6 +11,8 @@
#include <linux/syscalls.h>
#include <linux/slab.h>
#include <linux/sched.h>
+#include <linux/spinlock.h>
+#include <linux/percpu.h>
#include <linux/smp_lock.h>
#include <linux/init.h>
#include <linux/kernel.h>
@@ -37,12 +39,16 @@
#define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head))
#define HASH_SIZE (1UL << HASH_SHIFT)

-/* spinlock for vfsmount related operations, inplace of dcache_lock */
-__cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock);
+/*
+ * vfsmount "brlock" style spinlock for vfsmount related operations, use
+ * vfsmount_read_lock/vfsmount_write_lock functions.
+ */
+static DEFINE_PER_CPU(spinlock_t, vfsmount_lock);

static int event;
static DEFINE_IDA(mnt_id_ida);
static DEFINE_IDA(mnt_group_ida);
+static DEFINE_SPINLOCK(mnt_id_lock);
static int mnt_id_start = 0;
static int mnt_group_start = 1;

@@ -54,6 +60,49 @@ static struct rw_semaphore namespace_sem
struct kobject *fs_kobj;
EXPORT_SYMBOL_GPL(fs_kobj);

+void vfsmount_read_lock(void)
+{
+ spinlock_t *lock;
+
+ lock = &get_cpu_var(vfsmount_lock);
+ spin_lock(lock);
+}
+
+void vfsmount_read_unlock(void)
+{
+ spinlock_t *lock;
+
+ lock = &__get_cpu_var(vfsmount_lock);
+ spin_unlock(lock);
+ put_cpu_var(vfsmount_lock);
+}
+
+void vfsmount_write_lock(void)
+{
+ int i;
+ int nr = 0;
+
+ for_each_possible_cpu(i) {
+ spinlock_t *lock;
+
+ lock = &per_cpu(vfsmount_lock, i);
+ spin_lock_nested(lock, nr);
+ nr++;
+ }
+}
+
+void vfsmount_write_unlock(void)
+{
+ int i;
+
+ for_each_possible_cpu(i) {
+ spinlock_t *lock;
+
+ lock = &per_cpu(vfsmount_lock, i);
+ spin_unlock(lock);
+ }
+}
+
static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
{
unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
@@ -64,18 +113,21 @@ static inline unsigned long hash(struct

#define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16)

-/* allocation is serialized by namespace_sem */
+/*
+ * allocation is serialized by namespace_sem, but we need the spinlock to
+ * serialise with freeing.
+ */
static int mnt_alloc_id(struct vfsmount *mnt)
{
int res;

retry:
ida_pre_get(&mnt_id_ida, GFP_KERNEL);
- spin_lock(&vfsmount_lock);
+ spin_lock(&mnt_id_lock);
res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id);
if (!res)
mnt_id_start = mnt->mnt_id + 1;
- spin_unlock(&vfsmount_lock);
+ spin_unlock(&mnt_id_lock);
if (res == -EAGAIN)
goto retry;

@@ -85,11 +137,11 @@ retry:
static void mnt_free_id(struct vfsmount *mnt)
{
int id = mnt->mnt_id;
- spin_lock(&vfsmount_lock);
+ spin_lock(&mnt_id_lock);
ida_remove(&mnt_id_ida, id);
if (mnt_id_start > id)
mnt_id_start = id;
- spin_unlock(&vfsmount_lock);
+ spin_unlock(&mnt_id_lock);
}

/*
@@ -344,7 +396,7 @@ static int mnt_make_readonly(struct vfsm
{
int ret = 0;

- spin_lock(&vfsmount_lock);
+ vfsmount_write_lock();
mnt->mnt_flags |= MNT_WRITE_HOLD;
/*
* After storing MNT_WRITE_HOLD, we'll read the counters. This store
@@ -378,15 +430,15 @@ static int mnt_make_readonly(struct vfsm
*/
smp_wmb();
mnt->mnt_flags &= ~MNT_WRITE_HOLD;
- spin_unlock(&vfsmount_lock);
+ vfsmount_write_unlock();
return ret;
}

static void __mnt_unmake_readonly(struct vfsmount *mnt)
{
- spin_lock(&vfsmount_lock);
+ vfsmount_write_lock();
mnt->mnt_flags &= ~MNT_READONLY;
- spin_unlock(&vfsmount_lock);
+ vfsmount_write_unlock();
}

void simple_set_mnt(struct vfsmount *mnt, struct super_block *sb)
@@ -439,10 +491,11 @@ struct vfsmount *__lookup_mnt(struct vfs
struct vfsmount *lookup_mnt(struct path *path)
{
struct vfsmount *child_mnt;
- spin_lock(&vfsmount_lock);
+
+ vfsmount_read_lock();
if ((child_mnt = __lookup_mnt(path->mnt, path->dentry, 1)))
mntget(child_mnt);
- spin_unlock(&vfsmount_lock);
+ vfsmount_read_unlock();
return child_mnt;
}

@@ -618,40 +671,47 @@ static inline void __mntput(struct vfsmo
void mntput_no_expire(struct vfsmount *mnt)
{
repeat:
- if (atomic_dec_and_lock(&mnt->mnt_count, &vfsmount_lock)) {
- if (likely(!mnt->mnt_pinned)) {
- spin_unlock(&vfsmount_lock);
- __mntput(mnt);
- return;
- }
- atomic_add(mnt->mnt_pinned + 1, &mnt->mnt_count);
- mnt->mnt_pinned = 0;
- spin_unlock(&vfsmount_lock);
- acct_auto_close_mnt(mnt);
- security_sb_umount_close(mnt);
- goto repeat;
+ /* open-code atomic_dec_and_lock for the vfsmount lock */
+ if (atomic_add_unless(&mnt->mnt_count, -1, 1))
+ return;
+ vfsmount_write_lock();
+ if (!atomic_dec_and_test(&mnt->mnt_count)) {
+ vfsmount_write_unlock();
+ return;
}
+
+ if (likely(!mnt->mnt_pinned)) {
+ vfsmount_write_unlock();
+ __mntput(mnt);
+ return;
+ }
+ atomic_add(mnt->mnt_pinned + 1, &mnt->mnt_count);
+ mnt->mnt_pinned = 0;
+ vfsmount_write_unlock();
+ acct_auto_close_mnt(mnt);
+ security_sb_umount_close(mnt);
+ goto repeat;
}

EXPORT_SYMBOL(mntput_no_expire);

void mnt_pin(struct vfsmount *mnt)
{
- spin_lock(&vfsmount_lock);
+ vfsmount_write_lock();
mnt->mnt_pinned++;
- spin_unlock(&vfsmount_lock);
+ vfsmount_write_unlock();
}

EXPORT_SYMBOL(mnt_pin);

void mnt_unpin(struct vfsmount *mnt)
{
- spin_lock(&vfsmount_lock);
+ vfsmount_write_lock();
if (mnt->mnt_pinned) {
atomic_inc(&mnt->mnt_count);
mnt->mnt_pinned--;
}
- spin_unlock(&vfsmount_lock);
+ vfsmount_write_unlock();
}

EXPORT_SYMBOL(mnt_unpin);
@@ -934,12 +994,12 @@ int may_umount_tree(struct vfsmount *mnt
int minimum_refs = 0;
struct vfsmount *p;

- spin_lock(&vfsmount_lock);
+ vfsmount_read_lock();
for (p = mnt; p; p = next_mnt(p, mnt)) {
actual_refs += atomic_read(&p->mnt_count);
minimum_refs += 2;
}
- spin_unlock(&vfsmount_lock);
+ vfsmount_read_unlock();

if (actual_refs > minimum_refs)
return 0;
@@ -965,10 +1025,12 @@ EXPORT_SYMBOL(may_umount_tree);
int may_umount(struct vfsmount *mnt)
{
int ret = 1;
- spin_lock(&vfsmount_lock);
+
+ vfsmount_read_lock();
if (propagate_mount_busy(mnt, 2))
ret = 0;
- spin_unlock(&vfsmount_lock);
+ vfsmount_read_unlock();
+
return ret;
}

@@ -983,13 +1045,14 @@ void release_mounts(struct list_head *he
if (mnt->mnt_parent != mnt) {
struct dentry *dentry;
struct vfsmount *m;
- spin_lock(&vfsmount_lock);
+
+ vfsmount_write_lock();
dentry = mnt->mnt_mountpoint;
m = mnt->mnt_parent;
mnt->mnt_mountpoint = mnt->mnt_root;
mnt->mnt_parent = mnt;
m->mnt_ghosts--;
- spin_unlock(&vfsmount_lock);
+ vfsmount_write_unlock();
dput(dentry);
mntput(m);
}
@@ -1087,7 +1150,7 @@ static int do_umount(struct vfsmount *mn
}

down_write(&namespace_sem);
- spin_lock(&vfsmount_lock);
+ vfsmount_write_lock();
event++;

if (!(flags & MNT_DETACH))
@@ -1099,7 +1162,7 @@ static int do_umount(struct vfsmount *mn
umount_tree(mnt, 1, &umount_list);
retval = 0;
}
- spin_unlock(&vfsmount_lock);
+ vfsmount_write_unlock();
if (retval)
security_sb_umount_busy(mnt);
up_write(&namespace_sem);
@@ -1206,19 +1269,19 @@ struct vfsmount *copy_tree(struct vfsmou
q = clone_mnt(p, p->mnt_root, flag);
if (!q)
goto Enomem;
- spin_lock(&vfsmount_lock);
+ vfsmount_write_lock();
list_add_tail(&q->mnt_list, &res->mnt_list);
attach_mnt(q, &path);
- spin_unlock(&vfsmount_lock);
+ vfsmount_write_unlock();
}
}
return res;
Enomem:
if (res) {
LIST_HEAD(umount_list);
- spin_lock(&vfsmount_lock);
+ vfsmount_write_lock();
umount_tree(res, 0, &umount_list);
- spin_unlock(&vfsmount_lock);
+ vfsmount_write_unlock();
release_mounts(&umount_list);
}
return NULL;
@@ -1237,9 +1300,9 @@ void drop_collected_mounts(struct vfsmou
{
LIST_HEAD(umount_list);
down_write(&namespace_sem);
- spin_lock(&vfsmount_lock);
+ vfsmount_write_lock();
umount_tree(mnt, 0, &umount_list);
- spin_unlock(&vfsmount_lock);
+ vfsmount_write_unlock();
up_write(&namespace_sem);
release_mounts(&umount_list);
}
@@ -1357,7 +1420,7 @@ static int attach_recursive_mnt(struct v
set_mnt_shared(p);
}

- spin_lock(&vfsmount_lock);
+ vfsmount_write_lock();
if (parent_path) {
detach_mnt(source_mnt, parent_path);
attach_mnt(source_mnt, path);
@@ -1371,7 +1434,8 @@ static int attach_recursive_mnt(struct v
list_del_init(&child->mnt_hash);
commit_tree(child);
}
- spin_unlock(&vfsmount_lock);
+ vfsmount_write_unlock();
+
return 0;

out_cleanup_ids:
@@ -1433,10 +1497,10 @@ static int do_change_type(struct path *p
goto out_unlock;
}

- spin_lock(&vfsmount_lock);
+ vfsmount_write_lock();
for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
change_mnt_propagation(m, type);
- spin_unlock(&vfsmount_lock);
+ vfsmount_write_unlock();

out_unlock:
up_write(&namespace_sem);
@@ -1480,9 +1544,10 @@ static int do_loopback(struct path *path
err = graft_tree(mnt, path);
if (err) {
LIST_HEAD(umount_list);
- spin_lock(&vfsmount_lock);
+
+ vfsmount_write_lock();
umount_tree(mnt, 0, &umount_list);
- spin_unlock(&vfsmount_lock);
+ vfsmount_write_unlock();
release_mounts(&umount_list);
}

@@ -1540,9 +1605,9 @@ static int do_remount(struct path *path,
if (!err) {
security_sb_post_remount(path->mnt, flags, data);

- spin_lock(&vfsmount_lock);
+ vfsmount_write_lock();
touch_mnt_namespace(path->mnt->mnt_ns);
- spin_unlock(&vfsmount_lock);
+ vfsmount_write_unlock();
}
return err;
}
@@ -1717,7 +1782,7 @@ void mark_mounts_for_expiry(struct list_
return;

down_write(&namespace_sem);
- spin_lock(&vfsmount_lock);
+ vfsmount_write_lock();

/* extract from the expiration list every vfsmount that matches the
* following criteria:
@@ -1736,7 +1801,7 @@ void mark_mounts_for_expiry(struct list_
touch_mnt_namespace(mnt->mnt_ns);
umount_tree(mnt, 1, &umounts);
}
- spin_unlock(&vfsmount_lock);
+ vfsmount_write_unlock();
up_write(&namespace_sem);

release_mounts(&umounts);
@@ -1996,9 +2061,9 @@ static struct mnt_namespace *dup_mnt_ns(
kfree(new_ns);
return ERR_PTR(-ENOMEM);
}
- spin_lock(&vfsmount_lock);
+ vfsmount_write_lock();
list_add_tail(&new_ns->list, &new_ns->root->mnt_list);
- spin_unlock(&vfsmount_lock);
+ vfsmount_write_unlock();

/*
* Second pass: switch the tsk->fs->* elements and mark new vfsmounts
@@ -2193,7 +2258,7 @@ SYSCALL_DEFINE2(pivot_root, const char _
goto out2; /* not attached */
/* make sure we can reach put_old from new_root */
tmp = old.mnt;
- spin_lock(&vfsmount_lock);
+ vfsmount_write_lock();
if (tmp != new.mnt) {
for (;;) {
if (tmp->mnt_parent == tmp)
@@ -2213,7 +2278,7 @@ SYSCALL_DEFINE2(pivot_root, const char _
/* mount new_root on / */
attach_mnt(new.mnt, &root_parent);
touch_mnt_namespace(current->nsproxy->mnt_ns);
- spin_unlock(&vfsmount_lock);
+ vfsmount_write_unlock();
chroot_fs_refs(&root, &new);
security_sb_post_pivotroot(&root, &new);
error = 0;
@@ -2229,7 +2294,7 @@ out1:
out0:
return error;
out3:
- spin_unlock(&vfsmount_lock);
+ vfsmount_write_unlock();
goto out2;
}

@@ -2259,6 +2324,7 @@ static void __init init_mount_tree(void)
void __init mnt_init(void)
{
unsigned u;
+ int i;
int err;

init_rwsem(&namespace_sem);
@@ -2276,6 +2342,9 @@ void __init mnt_init(void)
for (u = 0; u < HASH_SIZE; u++)
INIT_LIST_HEAD(&mount_hashtable[u]);

+ for_each_possible_cpu(i)
+ spin_lock_init(&per_cpu(vfsmount_lock, i));
+
err = sysfs_init();
if (err)
printk(KERN_WARNING "%s: sysfs_init error: %d\n",
@@ -2291,16 +2360,22 @@ void put_mnt_ns(struct mnt_namespace *ns
{
struct vfsmount *root;
LIST_HEAD(umount_list);
+ spinlock_t *lock;

- if (!atomic_dec_and_lock(&ns->count, &vfsmount_lock))
+ lock = &get_cpu_var(vfsmount_lock);
+ if (!atomic_dec_and_lock(&ns->count, lock)) {
+ put_cpu_var(vfsmount_lock);
return;
+ }
root = ns->root;
ns->root = NULL;
- spin_unlock(&vfsmount_lock);
+ spin_unlock(lock);
+ put_cpu_var(vfsmount_lock);
+
down_write(&namespace_sem);
- spin_lock(&vfsmount_lock);
- umount_tree(root, 0, &umount_list);
- spin_unlock(&vfsmount_lock);
+ vfsmount_write_lock();
+ umount_tree(root, 0, &umount_list);
+ vfsmount_write_unlock();
up_write(&namespace_sem);
release_mounts(&umount_list);
kfree(ns);
Index: linux-2.6/fs/pnode.c
===================================================================
--- linux-2.6.orig/fs/pnode.c
+++ linux-2.6/fs/pnode.c
@@ -264,12 +264,12 @@ int propagate_mnt(struct vfsmount *dest_
prev_src_mnt = child;
}
out:
- spin_lock(&vfsmount_lock);
+ vfsmount_write_lock();
while (!list_empty(&tmp_list)) {
child = list_first_entry(&tmp_list, struct vfsmount, mnt_hash);
umount_tree(child, 0, &umount_list);
}
- spin_unlock(&vfsmount_lock);
+ vfsmount_write_unlock();
release_mounts(&umount_list);
return ret;
}
Index: linux-2.6/fs/proc/base.c
===================================================================
--- linux-2.6.orig/fs/proc/base.c
+++ linux-2.6/fs/proc/base.c
@@ -652,12 +652,12 @@ static unsigned mounts_poll(struct file

poll_wait(file, &ns->poll, wait);

- spin_lock(&vfsmount_lock);
+ vfsmount_read_lock();
if (p->event != ns->event) {
p->event = ns->event;
res |= POLLERR | POLLPRI;
}
- spin_unlock(&vfsmount_lock);
+ vfsmount_read_unlock();

return res;
}
Index: linux-2.6/include/linux/mount.h
===================================================================
--- linux-2.6.orig/include/linux/mount.h
+++ linux-2.6/include/linux/mount.h
@@ -90,6 +90,11 @@ static inline struct vfsmount *mntget(st

struct file; /* forward dec */

+extern void vfsmount_read_lock(void);
+extern void vfsmount_read_unlock(void);
+extern void vfsmount_write_lock(void);
+extern void vfsmount_write_unlock(void);
+
extern int mnt_want_write(struct vfsmount *mnt);
extern int mnt_want_write_file(struct file *file);
extern int mnt_clone_write(struct vfsmount *mnt);
@@ -123,7 +128,6 @@ extern int do_add_mount(struct vfsmount

extern void mark_mounts_for_expiry(struct list_head *mounts);

-extern spinlock_t vfsmount_lock;
extern dev_t name_to_dev_t(char *name);

#endif /* _LINUX_MOUNT_H */
Index: linux-2.6/kernel/audit_tree.c
===================================================================
--- linux-2.6.orig/kernel/audit_tree.c
+++ linux-2.6/kernel/audit_tree.c
@@ -758,15 +758,15 @@ int audit_tag_tree(char *old, char *new)
continue;
}

- spin_lock(&vfsmount_lock);
+ vfsmount_read_lock();
if (!is_under(mnt, dentry, &path)) {
- spin_unlock(&vfsmount_lock);
+ vfsmount_read_unlock();
path_put(&path);
put_tree(tree);
mutex_lock(&audit_filter_mutex);
continue;
}
- spin_unlock(&vfsmount_lock);
+ vfsmount_read_unlock();
path_put(&path);

list_for_each_entry(p, &list, mnt_list) {
Index: linux-2.6/security/tomoyo/realpath.c
===================================================================
--- linux-2.6.orig/security/tomoyo/realpath.c
+++ linux-2.6/security/tomoyo/realpath.c
@@ -96,12 +96,12 @@ int tomoyo_realpath_from_path2(struct pa
root = current->fs->root;
path_get(&root);
read_unlock(&current->fs->lock);
- spin_lock(&vfsmount_lock);
+ vfsmount_read_lock();
if (root.mnt && root.mnt->mnt_ns)
ns_root.mnt = mntget(root.mnt->mnt_ns->root);
if (ns_root.mnt)
ns_root.dentry = dget(ns_root.mnt->mnt_root);
- spin_unlock(&vfsmount_lock);
+ vfsmount_read_unlock();
spin_lock(&dcache_lock);
tmp = ns_root;
sp = __d_path(path, &tmp, newname, newname_len);



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