[PATCH 06/28] reintroduce list of vfsmounts over superblock

Dave Hansen
2006-08-01T23:59:51Z

We're moving a big chunk of the burden of keeping people from
writing to r/o filesystems from the superblock into the
vfsmount. This requires that we consult the superblock's
vfsmounts when things like remounts occur.

So, introduce a list of vfsmounts hanging off the superblock.
We'll use this in a bit.

Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
---

lxc-dave/fs/namespace.c | 12 ++++++++++++
lxc-dave/fs/super.c | 1 +
lxc-dave/include/linux/fs.h | 1 +
lxc-dave/include/linux/mount.h | 1 +
4 files changed, 15 insertions(+)

diff -puN fs/namespace.c~C-reintroduce-list-of-vfsmounts-over-superblock fs/namespace.c
--- lxc/fs/namespace.c~C-reintroduce-list-of-vfsmounts-over-superblock 2006-08-01 16:35:11.000000000 -0700
+++ lxc-dave/fs/namespace.c 2006-08-01 16:35:18.000000000 -0700
@@ -78,10 +78,18 @@ struct vfsmount *alloc_vfsmnt(const char
return mnt;
}

+void add_mount_to_sb_list(struct vfsmount *mnt, struct super_block *sb)
+{
+ spin_lock(&vfsmount_lock);
+ list_add(&mnt->mnt_sb_list, &sb->s_vfsmounts);
+ spin_unlock(&vfsmount_lock);
+}
+
int simple_set_mnt(struct vfsmount *mnt, struct super_block *sb)
{
mnt->mnt_sb = sb;
mnt->mnt_root = dget(sb->s_root);
+ add_mount_to_sb_list(mnt, sb);
return 0;
}

@@ -89,6 +97,9 @@ EXPORT_SYMBOL(simple_set_mnt);

void free_vfsmnt(struct vfsmount *mnt)
{
+ spin_lock(&vfsmount_lock);
+ list_del(&mnt->mnt_sb_list);
+ spin_unlock(&vfsmount_lock);
kfree(mnt->mnt_devname);
kmem_cache_free(mnt_cache, mnt);
}
@@ -242,6 +253,7 @@ static struct vfsmount *clone_mnt(struct
mnt->mnt_root = dget(root);
mnt->mnt_mountpoint = mnt->mnt_root;
mnt->mnt_parent = mnt;
+ add_mount_to_sb_list(mnt, sb);

if (flag & CL_SLAVE) {
list_add(&mnt->mnt_slave, &old->mnt_slave_list);
diff -puN fs/super.c~C-reintroduce-list-of-vfsmounts-over-superblock fs/super.c
--- lxc/fs/super.c~C-reintroduce-list-of-vfsmounts-over-superblock 2006-08-01 16:35:11.000000000 -0700
+++ lxc-dave/fs/super.c 2006-08-01 16:35:18.000000000 -0700
@@ -67,6 +67,7 @@ static struct super_block *alloc_super(s
INIT_LIST_HEAD(&s->s_dirty);
INIT_LIST_HEAD(&s->s_io);
INIT_LIST_HEAD(&s->s_files);
+ INIT_LIST_HEAD(&s->s_vfsmounts);
INIT_LIST_HEAD(&s->s_instances);
INIT_HLIST_HEAD(&s->s_anon);
INIT_LIST_HEAD(&s->s_inodes);
diff -puN include/linux/fs.h~C-reintroduce-list-of-vfsmounts-over-superblock include/linux/fs.h
--- lxc/include/linux/fs.h~C-reintroduce-list-of-vfsmounts-over-superblock 2006-08-01 16:35:17.000000000 -0700
+++ lxc-dave/include/linux/fs.h 2006-08-01 16:35:18.000000000 -0700
@@ -962,6 +962,7 @@ struct super_block {
struct list_head s_dirty; /* dirty inodes */
struct list_head s_io; /* parked for writeback */
struct hlist_head s_anon; /* anonymous dentries for (nfs) exporting */
+ struct list_head s_vfsmounts;
struct list_head s_files;

struct block_device *s_bdev;
diff -puN include/linux/mount.h~C-reintroduce-list-of-vfsmounts-over-superblock include/linux/mount.h
--- lxc/include/linux/mount.h~C-reintroduce-list-of-vfsmounts-over-superblock 2006-08-01 16:35:11.000000000 -0700
+++ lxc-dave/include/linux/mount.h 2006-08-01 16:35:18.000000000 -0700
@@ -40,6 +40,7 @@ struct vfsmount {
struct dentry *mnt_mountpoint; /* dentry of mountpoint */
struct dentry *mnt_root; /* root of the mounted tree */
struct super_block *mnt_sb; /* pointer to superblock */
+ struct list_head mnt_sb_list; /* list of all mounts on same sb */
struct list_head mnt_mounts; /* list of children, anchored here */
struct list_head mnt_child; /* and going through their mnt_child */
atomic_t mnt_count;
_