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get rid of ->mnt_longterm

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it's enough to set ->mnt_ns of internal vfsmounts to something
distinct from all struct mnt_namespace out there; then we can
just use the check for ->mnt_ns != NULL in the fast path of
mntput_no_expire()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2012-06-09 00:59:08 -04:00
parent d187663ef2
commit f7a99c5b7c
5 changed files with 26 additions and 72 deletions
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2
fs/dcache.c
View File

@ -2622,7 +2622,7 @@ global_root:
if (!slash)
error = prepend(buffer, buflen, "/", 1);
if (!error)
error = real_mount(vfsmnt)->mnt_ns ? 1 : 2;
error = is_mounted(vfsmnt) ? 1 : 2;
goto out;
}

32
fs/fs_struct.c
View File

@ -6,18 +6,6 @@
#include <linux/fs_struct.h>
#include "internal.h"
static inline void path_get_longterm(struct path *path)
{
path_get(path);
mnt_make_longterm(path->mnt);
}
static inline void path_put_longterm(struct path *path)
{
mnt_make_shortterm(path->mnt);
path_put(path);
}
/*
* Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
* It can block.
@ -26,7 +14,7 @@ void set_fs_root(struct fs_struct *fs, struct path *path)
{
struct path old_root;
path_get_longterm(path);
path_get(path);
spin_lock(&fs->lock);
write_seqcount_begin(&fs->seq);
old_root = fs->root;
@ -34,7 +22,7 @@ void set_fs_root(struct fs_struct *fs, struct path *path)
write_seqcount_end(&fs->seq);
spin_unlock(&fs->lock);
if (old_root.dentry)
path_put_longterm(&old_root);
path_put(&old_root);
}
/*
@ -45,7 +33,7 @@ void set_fs_pwd(struct fs_struct *fs, struct path *path)
{
struct path old_pwd;
path_get_longterm(path);
path_get(path);
spin_lock(&fs->lock);
write_seqcount_begin(&fs->seq);
old_pwd = fs->pwd;
@ -54,7 +42,7 @@ void set_fs_pwd(struct fs_struct *fs, struct path *path)
spin_unlock(&fs->lock);
if (old_pwd.dentry)
path_put_longterm(&old_pwd);
path_put(&old_pwd);
}
static inline int replace_path(struct path *p, const struct path *old, const struct path *new)
@ -84,7 +72,7 @@ void chroot_fs_refs(struct path *old_root, struct path *new_root)
write_seqcount_end(&fs->seq);
while (hits--) {
count++;
path_get_longterm(new_root);
path_get(new_root);
}
spin_unlock(&fs->lock);
}
@ -92,13 +80,13 @@ void chroot_fs_refs(struct path *old_root, struct path *new_root)
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
while (count--)
path_put_longterm(old_root);
path_put(old_root);
}
void free_fs_struct(struct fs_struct *fs)
{
path_put_longterm(&fs->root);
path_put_longterm(&fs->pwd);
path_put(&fs->root);
path_put(&fs->pwd);
kmem_cache_free(fs_cachep, fs);
}
@ -132,9 +120,9 @@ struct fs_struct *copy_fs_struct(struct fs_struct *old)
spin_lock(&old->lock);
fs->root = old->root;
path_get_longterm(&fs->root);
path_get(&fs->root);
fs->pwd = old->pwd;
path_get_longterm(&fs->pwd);
path_get(&fs->pwd);
spin_unlock(&old->lock);
}
return fs;

2
fs/internal.h
View File

@ -50,8 +50,6 @@ extern int copy_mount_string(const void __user *, char **);
extern struct vfsmount *lookup_mnt(struct path *);
extern int finish_automount(struct vfsmount *, struct path *);
extern void mnt_make_longterm(struct vfsmount *);
extern void mnt_make_shortterm(struct vfsmount *);
extern int sb_prepare_remount_readonly(struct super_block *);
extern void __init mnt_init(void);

9
fs/mount.h
View File

@ -22,7 +22,6 @@ struct mount {
struct vfsmount mnt;
#ifdef CONFIG_SMP
struct mnt_pcp __percpu *mnt_pcp;
atomic_t mnt_longterm; /* how many of the refs are longterm */
#else
int mnt_count;
int mnt_writers;
@ -49,6 +48,8 @@ struct mount {
int mnt_ghosts;
};
#define MNT_NS_INTERNAL ERR_PTR(-EINVAL) /* distinct from any mnt_namespace */
static inline struct mount *real_mount(struct vfsmount *mnt)
{
return container_of(mnt, struct mount, mnt);
@ -59,6 +60,12 @@ static inline int mnt_has_parent(struct mount *mnt)
return mnt != mnt->mnt_parent;
}
static inline int is_mounted(struct vfsmount *mnt)
{
/* neither detached nor internal? */
return !IS_ERR_OR_NULL(real_mount(mnt));
}
extern struct mount *__lookup_mnt(struct vfsmount *, struct dentry *, int);
static inline void get_mnt_ns(struct mnt_namespace *ns)

53
fs/namespace.c
View File

@ -621,21 +621,6 @@ static void attach_mnt(struct mount *mnt, struct path *path)
list_add_tail(&mnt->mnt_child, &real_mount(path->mnt)->mnt_mounts);
}
static inline void __mnt_make_longterm(struct mount *mnt)
{
#ifdef CONFIG_SMP
atomic_inc(&mnt->mnt_longterm);
#endif
}
/* needs vfsmount lock for write */
static inline void __mnt_make_shortterm(struct mount *mnt)
{
#ifdef CONFIG_SMP
atomic_dec(&mnt->mnt_longterm);
#endif
}
/*
* vfsmount lock must be held for write
*/
@ -649,10 +634,8 @@ static void commit_tree(struct mount *mnt)
BUG_ON(parent == mnt);
list_add_tail(&head, &mnt->mnt_list);
list_for_each_entry(m, &head, mnt_list) {
list_for_each_entry(m, &head, mnt_list)
m->mnt_ns = n;
__mnt_make_longterm(m);
}
list_splice(&head, n->list.prev);
@ -804,7 +787,8 @@ static void mntput_no_expire(struct mount *mnt)
put_again:
#ifdef CONFIG_SMP
br_read_lock(&vfsmount_lock);
if (likely(atomic_read(&mnt->mnt_longterm))) {
if (likely(mnt->mnt_ns)) {
/* shouldn't be the last one */
mnt_add_count(mnt, -1);
br_read_unlock(&vfsmount_lock);
return;
@ -1074,8 +1058,6 @@ void umount_tree(struct mount *mnt, int propagate, struct list_head *kill)
list_del_init(&p->mnt_expire);
list_del_init(&p->mnt_list);
__touch_mnt_namespace(p->mnt_ns);
if (p->mnt_ns)
__mnt_make_shortterm(p);
p->mnt_ns = NULL;
list_del_init(&p->mnt_child);
if (mnt_has_parent(p)) {
@ -2209,23 +2191,6 @@ static struct mnt_namespace *alloc_mnt_ns(void)
return new_ns;
}
void mnt_make_longterm(struct vfsmount *mnt)
{
__mnt_make_longterm(real_mount(mnt));
}
void mnt_make_shortterm(struct vfsmount *m)
{
#ifdef CONFIG_SMP
struct mount *mnt = real_mount(m);
if (atomic_add_unless(&mnt->mnt_longterm, -1, 1))
return;
br_write_lock(&vfsmount_lock);
atomic_dec(&mnt->mnt_longterm);
br_write_unlock(&vfsmount_lock);
#endif
}
/*
* Allocate a new namespace structure and populate it with contents
* copied from the namespace of the passed in task structure.
@ -2265,18 +2230,13 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
q = new;
while (p) {
q->mnt_ns = new_ns;
__mnt_make_longterm(q);
if (fs) {
if (&p->mnt == fs->root.mnt) {
fs->root.mnt = mntget(&q->mnt);
__mnt_make_longterm(q);
mnt_make_shortterm(&p->mnt);
rootmnt = &p->mnt;
}
if (&p->mnt == fs->pwd.mnt) {
fs->pwd.mnt = mntget(&q->mnt);
__mnt_make_longterm(q);
mnt_make_shortterm(&p->mnt);
pwdmnt = &p->mnt;
}
}
@ -2320,7 +2280,6 @@ static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
if (!IS_ERR(new_ns)) {
struct mount *mnt = real_mount(m);
mnt->mnt_ns = new_ns;
__mnt_make_longterm(mnt);
new_ns->root = mnt;
list_add(&new_ns->list, &mnt->mnt_list);
} else {
@ -2615,7 +2574,7 @@ struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
* it is a longterm mount, don't release mnt until
* we unmount before file sys is unregistered
*/
mnt_make_longterm(mnt);
real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
}
return mnt;
}
@ -2625,7 +2584,9 @@ 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);
br_write_lock(&vfsmount_lock);
real_mount(mnt)->mnt_ns = NULL;
br_write_unlock(&vfsmount_lock);
mntput(mnt);
}
}