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Subject[RFC-2 PATCH 5/8] shared subtree
Adds ability to unmount a shared/slave/unclone/private tree

RP

Signed by Ram Pai (linuxram@us.ibm.com)

fs/namespace.c | 68 +++++++++++++++++++++++++-----
fs/pnode.c | 112 ++++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/fs.h | 3 +
include/linux/pnode.h | 5 ++
4 files changed, 177 insertions(+), 11 deletions(-)
Index: 2.6.12.work1/fs/pnode.c
===================================================================
--- 2.6.12.work1.orig/fs/pnode.c
+++ 2.6.12.work1/fs/pnode.c
@@ -273,6 +273,117 @@ int pnode_merge_pnode(struct vfspnode *p
return 0;
}

+static int vfs_busy(struct vfsmount *mnt, struct dentry *dentry,
+ struct dentry *rootdentry, struct vfsmount *origmnt)
+{
+ struct vfsmount *child_mnt;
+ int ret=0;
+
+ spin_unlock(&vfsmount_lock);
+ child_mnt = __lookup_mnt(mnt, dentry, rootdentry);
+ spin_lock(&vfsmount_lock);
+
+ if (!child_mnt)
+ return 0;
+
+ if (list_empty(&child_mnt->mnt_mounts)) {
+ if (origmnt == child_mnt)
+ ret = do_refcount_check(child_mnt, 3);
+ else
+ ret = do_refcount_check(child_mnt, 2);
+ }
+ mntput(child_mnt);
+ return ret;
+}
+
+int pnode_mount_busy(struct vfspnode *pnode, struct dentry *mntpt,
+ struct dentry *root, struct vfsmount *mnt)
+{
+ int ret=0;
+ struct vfsmount *slave_mnt, *member_mnt, *t_m;
+ struct pcontext context;
+
+ context.start = pnode;
+ context.pnode = NULL;
+ while (pnode_next(&context)) {
+ pnode = context.pnode;
+
+ // traverse member vfsmounts
+ spin_lock(&vfspnode_lock);
+ list_for_each_entry_safe(member_mnt,
+ t_m, &pnode->pnode_vfs, mnt_pnode_mntlist) {
+ spin_unlock(&vfspnode_lock);
+ if ((ret = vfs_busy(member_mnt, mntpt,
+ root, mnt)))
+ goto out;
+ spin_lock(&vfspnode_lock);
+ }
+ list_for_each_entry_safe(slave_mnt, t_m,
+ &pnode->pnode_slavevfs, mnt_pnode_mntlist) {
+ spin_unlock(&vfspnode_lock);
+ if ((ret = vfs_busy(slave_mnt, mntpt,
+ root, mnt)))
+ goto out;
+ spin_lock(&vfspnode_lock);
+ }
+ spin_unlock(&vfspnode_lock);
+ }
+out:
+ return ret;
+}
+
+int vfs_umount(struct vfsmount *mnt, struct dentry *dentry,
+ struct dentry *rootdentry)
+{
+ struct vfsmount *child_mnt;
+
+ spin_unlock(&vfsmount_lock);
+ child_mnt = __lookup_mnt(mnt, dentry, rootdentry);
+ spin_lock(&vfsmount_lock);
+ mntput(child_mnt);
+ if (child_mnt && list_empty(&child_mnt->mnt_mounts)) {
+ do_detach_mount(child_mnt);
+ if (child_mnt->mnt_pnode)
+ pnode_disassociate_mnt(child_mnt);
+ }
+ return 0;
+}
+
+int pnode_umount(struct vfspnode *pnode, struct dentry *dentry,
+ struct dentry *rootdentry)
+{
+ int ret=0;
+ struct vfsmount *slave_mnt, *member_mnt, *t_m;
+ struct pcontext context;
+
+ context.start = pnode;
+ context.pnode = NULL;
+ while (pnode_next(&context)) {
+ pnode = context.pnode;
+ // traverse member vfsmounts
+ spin_lock(&vfspnode_lock);
+ list_for_each_entry_safe(member_mnt,
+ t_m, &pnode->pnode_vfs, mnt_pnode_mntlist) {
+ spin_unlock(&vfspnode_lock);
+ if ((ret = vfs_umount(member_mnt,
+ dentry, rootdentry)))
+ goto out;
+ spin_lock(&vfspnode_lock);
+ }
+ list_for_each_entry_safe(slave_mnt, t_m,
+ &pnode->pnode_slavevfs, mnt_pnode_mntlist) {
+ spin_unlock(&vfspnode_lock);
+ if ((ret = vfs_umount(slave_mnt,
+ dentry, rootdentry)))
+ goto out;
+ spin_lock(&vfspnode_lock);
+ }
+ spin_unlock(&vfspnode_lock);
+ }
+out:
+ return ret;
+}
+
/*
* @pnode: pnode that contains the vfsmounts, on which the
* new mount is created at dentry 'dentry'
@@ -532,6 +643,7 @@ int pnode_real_mount(struct vfspnode *pn
if ((ret = vfs_real_mount_func(member_mnt,
flag)))
goto out;
+ spin_lock(&vfspnode_lock);
}
list_for_each_entry_safe(slave_mnt, t_m,
&pnode->pnode_slavevfs, mnt_pnode_mntlist) {
Index: 2.6.12.work1/fs/namespace.c
===================================================================
--- 2.6.12.work1.orig/fs/namespace.c
+++ 2.6.12.work1/fs/namespace.c
@@ -352,6 +352,7 @@ struct seq_operations mounts_op = {
* open files, pwds, chroots or sub mounts that are
* busy.
*/
+//TOBEFIXED
int may_umount_tree(struct vfsmount *mnt)
{
struct list_head *next;
@@ -394,6 +395,20 @@ resume:

EXPORT_SYMBOL(may_umount_tree);

+int mount_busy(struct vfsmount *mnt)
+{
+ struct vfspnode *parent_pnode;
+
+ if (mnt == mnt->mnt_parent || !IS_MNT_SHARED(mnt->mnt_parent))
+ return do_refcount_check(mnt, 2);
+
+ parent_pnode = mnt->mnt_parent->mnt_pnode;
+ BUG_ON(!parent_pnode);
+ return pnode_mount_busy(parent_pnode,
+ mnt->mnt_mountpoint,
+ mnt->mnt_root, mnt);
+}
+
/**
* may_umount - check if a mount point is busy
* @mnt: root of mount
@@ -409,13 +424,27 @@ EXPORT_SYMBOL(may_umount_tree);
*/
int may_umount(struct vfsmount *mnt)
{
- if (atomic_read(&mnt->mnt_count) > 2)
+ if (mount_busy(mnt))
return -EBUSY;
return 0;
}

EXPORT_SYMBOL(may_umount);

+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_fslink);
+ spin_unlock(&vfsmount_lock);
+ mntput(mnt);
+ spin_lock(&vfsmount_lock);
+}
+
void umount_tree(struct vfsmount *mnt)
{
struct vfsmount *p;
@@ -430,20 +459,35 @@ void umount_tree(struct vfsmount *mnt)
mnt = list_entry(kill.next, struct vfsmount, mnt_list);
list_del_init(&mnt->mnt_list);
list_del_init(&mnt->mnt_fslink);
- if (mnt->mnt_parent == mnt) {
- spin_unlock(&vfsmount_lock);
+ if (mnt->mnt_parent != mnt &&
+ IS_MNT_SHARED(mnt->mnt_parent)) {
+ struct vfspnode *parent_pnode
+ = mnt->mnt_parent->mnt_pnode;
+ BUG_ON(!parent_pnode);
+ pnode_umount(parent_pnode,
+ mnt->mnt_mountpoint,
+ mnt->mnt_root);
} else {
- struct nameidata old_nd;
- detach_mnt(mnt, &old_nd);
- spin_unlock(&vfsmount_lock);
- path_release(&old_nd);
+ if (IS_MNT_SHARED(mnt) || IS_MNT_SLAVE(mnt)) {
+ BUG_ON(!mnt->mnt_pnode);
+ pnode_disassociate_mnt(mnt);
+ }
+ do_detach_mount(mnt);
}
- mntput(mnt);
- spin_lock(&vfsmount_lock);
}
}

-static int do_umount(struct vfsmount *mnt, int flags)
+/*
+ * 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);
+}
+
+int do_umount(struct vfsmount *mnt, int flags)
{
struct super_block * sb = mnt->mnt_sb;
int retval;
@@ -524,7 +568,7 @@ static int do_umount(struct vfsmount *mn
spin_lock(&vfsmount_lock);
}
retval = -EBUSY;
- if (atomic_read(&mnt->mnt_count) == 2 || flags & MNT_DETACH) {
+ if (flags & MNT_DETACH || !mount_busy(mnt)) {
if (!list_empty(&mnt->mnt_list))
umount_tree(mnt);
retval = 0;
@@ -900,7 +944,9 @@ detach_recursive_mnt(struct vfsmount *so

detach_mnt(source_mnt, nd);
for (m = source_mnt; m; m = next_mnt(m, source_mnt)) {
+ spin_lock(&vfspnode_lock);
list_del_init(&m->mnt_pnode_mntlist);
+ spin_unlock(&vfspnode_lock);
}
return;
}
Index: 2.6.12.work1/include/linux/fs.h
===================================================================
--- 2.6.12.work1.orig/include/linux/fs.h
+++ 2.6.12.work1/include/linux/fs.h
@@ -1216,11 +1216,14 @@ extern struct vfsmount *kern_mount(struc
extern int may_umount_tree(struct vfsmount *);
extern int may_umount(struct vfsmount *);
extern long do_mount(char *, char *, char *, unsigned long, void *);
+extern int do_umount(struct vfsmount *, int);
extern struct vfsmount *do_attach_prepare_mnt(struct vfsmount *,
struct dentry *, struct vfsmount *, int );
extern void do_attach_real_mnt(struct vfsmount *);
extern struct vfsmount *do_make_mounted(struct vfsmount *, struct dentry *);
extern int do_make_unmounted(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 *);

Index: 2.6.12.work1/include/linux/pnode.h
===================================================================
--- 2.6.12.work1.orig/include/linux/pnode.h
+++ 2.6.12.work1/include/linux/pnode.h
@@ -70,6 +70,9 @@ put_pnode_locked(struct vfspnode *pnode)

void __init pnode_init(unsigned long );
struct vfspnode * pnode_alloc(void);
+void pnode_free(struct vfspnode *);
+int pnode_is_busy(struct vfspnode *);
+int pnode_umount_vfs(struct vfspnode *, struct dentry *, struct dentry *, int);
void pnode_add_slave_mnt(struct vfspnode *, struct vfsmount *);
void pnode_add_member_mnt(struct vfspnode *, struct vfsmount *);
void pnode_del_slave_mnt(struct vfsmount *);
@@ -82,4 +85,6 @@ int pnode_make_unmounted(struct vfspnod
int pnode_prepare_mount(struct vfspnode *, struct vfspnode *, struct dentry *,
struct vfsmount *, struct vfsmount *);
int pnode_real_mount(struct vfspnode *, int);
+int pnode_umount(struct vfspnode *, struct dentry *, struct dentry *);
+int pnode_mount_busy(struct vfspnode *, struct dentry *, struct dentry *, struct vfsmount *);
#endif /* _LINUX_PNODE_H */
-
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