Patch that help umount a mount. The mount can either be shared,slave,private or
unclonable.
An unmount of a mount creates a umount event on the parent. If the parent is
a shared mount, it gets propagated to all mounts down the propagation tree.
Signed by Ram Pai ([email protected])
fs/namespace.c | 68 ++++++++++++++++++++++++++++++-----------
fs/pnode.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/dcache.h | 1
include/linux/fs.h | 1
include/linux/pnode.h | 2 +
5 files changed, 134 insertions(+), 18 deletions(-)
Index: 2.6.13.sharedsubtree/fs/namespace.c
===================================================================
--- 2.6.13.sharedsubtree.orig/fs/namespace.c
+++ 2.6.13.sharedsubtree/fs/namespace.c
@@ -84,35 +84,48 @@ void free_vfsmnt(struct vfsmount *mnt)
kfree(mnt->mnt_devname);
kmem_cache_free(mnt_cache, mnt);
}
/*
- * Now, lookup_mnt increments the ref count before returning
- * the vfsmount struct.
+ * find the first or last mount at @dentry on vfsmount @mnt depending on
+ * @dir. If @dir is set return the first mount else return the last mount.
*/
-struct vfsmount *lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
+struct vfsmount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry,
+ int dir)
{
struct list_head *head = mount_hashtable + hash(mnt, dentry);
struct list_head *tmp = head;
struct vfsmount *p, *found = NULL;
- spin_lock(&vfsmount_lock);
for (;;) {
- tmp = tmp->next;
+ tmp = dir ? tmp->next : tmp->prev;
p = NULL;
if (tmp == head)
break;
p = list_entry(tmp, struct vfsmount, mnt_hash);
if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) {
- found = mntget(p);
+ found = p;
break;
}
}
- spin_unlock(&vfsmount_lock);
return found;
}
+/*
+ * lookup_mnt increments the ref count before returning
+ * the vfsmount struct.
+ */
+struct vfsmount *lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
+{
+ struct vfsmount *child_mnt;
+ spin_lock(&vfsmount_lock);
+ if ((child_mnt = __lookup_mnt(mnt, dentry, 1)))
+ mntget(child_mnt);
+ spin_unlock(&vfsmount_lock);
+ return child_mnt;
+}
+
static inline int check_mnt(struct vfsmount *mnt)
{
return mnt->mnt_namespace == current->namespace;
}
@@ -369,10 +382,29 @@ int may_umount_tree(struct vfsmount *mnt
return 0;
}
EXPORT_SYMBOL(may_umount_tree);
+int mount_busy(struct vfsmount *mnt)
+{
+ return propagate_mount_busy(mnt, 2);
+}
+
+void do_detach_mount(struct vfsmount *mnt)
+{
+ struct nameidata old_nd;
+ if (mnt != mnt->mnt_parent) {
+ detach_mnt(mnt, &old_nd);
+ path_release(&old_nd);
+ }
+ list_del_init(&mnt->mnt_list);
+ list_del_init(&mnt->mnt_expire);
+ spin_unlock(&vfsmount_lock);
+ mntput(mnt);
+ spin_lock(&vfsmount_lock);
+}
+
/**
* may_umount - check if a mount point is busy
* @mnt: root of mount
*
* This is called to check if a mount point has any
@@ -406,23 +438,23 @@ static void umount_tree(struct vfsmount
while (!list_empty(&kill)) {
mnt = list_entry(kill.next, struct vfsmount, mnt_list);
list_del_init(&mnt->mnt_list);
list_del_init(&mnt->mnt_expire);
- if (mnt->mnt_parent == mnt) {
- spin_unlock(&vfsmount_lock);
- } else {
- struct nameidata old_nd;
- detach_mnt(mnt, &old_nd);
- spin_unlock(&vfsmount_lock);
- path_release(&old_nd);
- }
- mntput(mnt);
- spin_lock(&vfsmount_lock);
+ propagate_umount(mnt);
}
}
+/*
+ * return true if the refcount is greater than count
+ */
+int do_refcount_check(struct vfsmount *mnt, int count)
+{
+ int mycount = atomic_read(&mnt->mnt_count);
+ return (mycount > count);
+}
+
static int do_umount(struct vfsmount *mnt, int flags)
{
struct super_block *sb = mnt->mnt_sb;
int retval;
@@ -500,11 +532,11 @@ static int do_umount(struct vfsmount *mn
unlock_kernel();
security_sb_umount_close(mnt);
spin_lock(&vfsmount_lock);
}
retval = -EBUSY;
- if (atomic_read(&mnt->mnt_count) == 2 || flags & MNT_DETACH) {
+ if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) {
if (!list_empty(&mnt->mnt_list))
umount_tree(mnt);
retval = 0;
}
spin_unlock(&vfsmount_lock);
Index: 2.6.13.sharedsubtree/fs/pnode.c
===================================================================
--- 2.6.13.sharedsubtree.orig/fs/pnode.c
+++ 2.6.13.sharedsubtree/fs/pnode.c
@@ -573,5 +573,85 @@ int propagate_prepare_mount(struct vfsmo
create_child_list(source_mnt, &tmp_list);
propagate_abort_mount(source_mnt);
spin_unlock(&vfspnode_lock);
return -ENOMEM;
}
+
+/*
+ * check if the mount 'mnt' can be unmounted successfully.
+ * @mnt: the mount to be checked for unmount
+ * NOTE: unmounting 'mnt' would naturally propagate to all
+ * other mounts its parent propagates to. Hence those mounts
+ * are also to be checked for unmount.
+ */
+int propagate_mount_busy(struct vfsmount *mnt, int refcnt)
+{
+ struct vfsmount *m, *child;
+ struct vfsmount *parent = mnt->mnt_parent;
+ int ret = 0;
+
+ if (mnt == parent)
+ return do_refcount_check(mnt, refcnt);
+
+ /*
+ * quickly check if the current mount can be unmounted.
+ * If not, we don't have to go checking for all other
+ * mounts
+ */
+ if (!list_empty(&mnt->mnt_mounts) || do_refcount_check(mnt, refcnt))
+ return 1;
+
+ spin_lock(&vfspnode_lock);
+ for (m = propagation_next(parent, parent); m;
+ m = propagation_next(m, parent)) {
+ child = __lookup_mnt(m, mnt->mnt_mountpoint, 0);
+ if (child && list_empty(&child->mnt_mounts) &&
+ (ret = do_refcount_check(child, 1)))
+ break;
+ }
+ spin_unlock(&vfspnode_lock);
+ return ret;
+}
+
+/*
+ * umount 'mnt' and also umount any mounts that gets the propagation.
+ * @mnt: the mount to be unmounted.
+ * NOTE: unmounting 'mnt' would naturally propagate to all
+ * other mounts its parent propagates to.
+ */
+int propagate_umount(struct vfsmount *mnt)
+{
+ struct vfsmount *m, *child;
+ struct vfsmount *parent = mnt->mnt_parent;
+ LIST_HEAD(mnt_list_head);
+
+ if (mnt == parent) {
+ do_detach_mount(mnt);
+ return 0;
+ }
+
+ list_del(&mnt->mnt_list);
+ list_add(&mnt->mnt_list, &mnt_list_head);
+
+ spin_lock(&vfspnode_lock);
+ for (m = propagation_next(parent, parent); m;
+ m = propagation_next(m, parent)) {
+ child = __lookup_mnt(m, mnt->mnt_mountpoint, 0);
+ /*
+ * unmount the child only if the child has no
+ * other children
+ */
+ if (child && list_empty(&child->mnt_mounts)) {
+ list_del(&child->mnt_list);
+ list_add(&child->mnt_list, &mnt_list_head);
+ }
+ }
+ spin_unlock(&vfspnode_lock);
+
+ while (!list_empty(&mnt_list_head)) {
+ m = list_entry(mnt_list_head.next, struct vfsmount, mnt_list);
+ list_del_init(&m->mnt_list);
+ do_make_private(m);
+ do_detach_mount(m);
+ }
+ return 0;
+}
Index: 2.6.13.sharedsubtree/include/linux/pnode.h
===================================================================
--- 2.6.13.sharedsubtree.orig/include/linux/pnode.h
+++ 2.6.13.sharedsubtree/include/linux/pnode.h
@@ -60,6 +60,8 @@ void pnode_merge_mount(struct vfsmount *
void pnode_slave_mount(struct vfsmount *, struct vfsmount *);
int propagate_commit_mount(struct vfsmount *);
int propagate_abort_mount(struct vfsmount *);
int propagate_prepare_mount(struct vfsmount *, struct dentry *,
struct vfsmount *);
+int propagate_umount(struct vfsmount *);
+int propagate_mount_busy(struct vfsmount *, int);
#endif /* _LINUX_PNODE_H */
Index: 2.6.13.sharedsubtree/include/linux/fs.h
===================================================================
--- 2.6.13.sharedsubtree.orig/include/linux/fs.h
+++ 2.6.13.sharedsubtree/include/linux/fs.h
@@ -1250,10 +1250,11 @@ extern struct vfsmount *clone_mnt(struct
extern void do_attach_prepare_mnt(struct vfsmount *, struct dentry *,
struct vfsmount *);
extern void do_attach_commit_mnt(struct vfsmount *);
extern void do_detach_prepare_mnt(struct vfsmount *);
extern void do_detach_mount(struct vfsmount *);
+extern int do_refcount_check(struct vfsmount *, int);
extern int vfs_statfs(struct super_block *, struct kstatfs *);
#define FLOCK_VERIFY_READ 1
#define FLOCK_VERIFY_WRITE 2
Index: 2.6.13.sharedsubtree/include/linux/dcache.h
===================================================================
--- 2.6.13.sharedsubtree.orig/include/linux/dcache.h
+++ 2.6.13.sharedsubtree/include/linux/dcache.h
@@ -327,10 +327,11 @@ static inline int d_mountpoint(struct de
{
return dentry->d_mounted;
}
extern struct vfsmount *lookup_mnt(struct vfsmount *, struct dentry *);
+extern struct vfsmount *__lookup_mnt(struct vfsmount *, struct dentry *, int);
extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
extern int sysctl_vfs_cache_pressure;
#endif /* __KERNEL__ */
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
| |
 |