mnt: Add filesystem private data to mount points

This starts to add private data associated directly
to mount points. The intent is to give filesystems
a sense of where they have come from, as a means of
letting a filesystem take different actions based on
this information.

Change-Id: Ie769d7b3bb2f5972afe05c1bf16cf88c91647ab2
Signed-off-by: Daniel Rosenberg <drosen@google.com>

diff --git a/fs/namespace.c b/fs/namespace.c
index 7ff6b812cbaf43a3bb8be96694c5b1c39af66340..6deff2e63e51bdfe9a10537fd53e6352810171cb 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -544,6 +544,7 @@ int sb_prepare_remount_readonly(struct super_block *sb)
 
 static void free_vfsmnt(struct mount *mnt)
 {
+       kfree(mnt->mnt.data);
        kfree(mnt->mnt_devname);
        mnt_free_id(mnt);
 #ifdef CONFIG_SMP
@@ -787,11 +788,21 @@ vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void
        if (!mnt)
                return ERR_PTR(-ENOMEM);
 
+       mnt->mnt.data = NULL;
+       if (type->alloc_mnt_data) {
+               mnt->mnt.data = type->alloc_mnt_data();
+               if (!mnt->mnt.data) {
+                       mnt_free_id(mnt);
+                       free_vfsmnt(mnt);
+                       return ERR_PTR(-ENOMEM);
+               }
+       }
        if (flags & MS_KERNMOUNT)
                mnt->mnt.mnt_flags = MNT_INTERNAL;
 
        root = mount_fs(type, flags, name, data);
        if (IS_ERR(root)) {
+               kfree(mnt->mnt.data);
                free_vfsmnt(mnt);
                return ERR_CAST(root);
        }
@@ -818,6 +829,14 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
        if (!mnt)
                return ERR_PTR(-ENOMEM);
 
+       if (sb->s_op->clone_mnt_data) {
+               mnt->mnt.data = sb->s_op->clone_mnt_data(old->mnt.data);
+               if (!mnt->mnt.data) {
+                       err = -ENOMEM;
+                       goto out_free;
+               }
+       }
+
        if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
                mnt->mnt_group_id = 0; /* not a peer of original */
        else
@@ -881,6 +900,7 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
        return mnt;
 
  out_free:
+       kfree(mnt->mnt.data);
        free_vfsmnt(mnt);
        return ERR_PTR(err);
 }
@@ -1846,8 +1866,14 @@ static int do_remount(struct path *path, int flags, int mnt_flags,
                err = change_mount_flags(path->mnt, flags);
        else if (!capable(CAP_SYS_ADMIN))
                err = -EPERM;
-       else
+       else {
                err = do_remount_sb(sb, flags, data, 0);
+               namespace_lock();
+               br_write_lock(&vfsmount_lock);
+               propagate_remount(mnt);
+               br_write_unlock(&vfsmount_lock);
+               namespace_unlock();
+       }
        if (!err) {
                br_write_lock(&vfsmount_lock);
                mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;

diff --git a/fs/pnode.c b/fs/pnode.c
index 9af0df15256e9405082fdb59d1a2c6fe97fb8e59..2ef946f51a11091b3bb96bbf7979907fc9d74f72 100644 (file)
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -359,3 +359,17 @@ int propagate_umount(struct list_head *list)
                __propagate_umount(mnt);
        return 0;
 }
+
+int propagate_remount(struct mount *mnt) {
+       struct mount *m;
+       struct super_block *sb = mnt->mnt.mnt_sb;
+       int ret = 0;
+
+       if (sb->s_op->copy_mnt_data) {
+               for (m = first_slave(mnt); m->mnt_slave.next != &mnt->mnt_slave_list; m = next_slave(m)) {
+                       sb->s_op->copy_mnt_data(m->mnt.data, mnt->mnt.data);
+               }
+       }
+
+       return ret;
+}

diff --git a/fs/pnode.h b/fs/pnode.h
index b091445c1c4ac4472c09adb54496f7af98060a42..ae8d67a9e9627018e67ca3ac755ea3855c62e5d4 100644 (file)
--- a/fs/pnode.h
+++ b/fs/pnode.h
@@ -36,6 +36,7 @@ int propagate_mnt(struct mount *, struct mountpoint *, struct mount *,
                struct list_head *);
 int propagate_umount(struct list_head *);
 int propagate_mount_busy(struct mount *, int);
+int propagate_remount(struct mount *);
 void mnt_release_group_id(struct mount *);
 int get_dominating_id(struct mount *mnt, const struct path *root);
 unsigned int mnt_get_count(struct mount *mnt);

diff --git a/include/linux/fs.h b/include/linux/fs.h
index cbbf11b1854efca9a5da7a6404b5dbe44976d44d..6ff36d296468820f5039840c7ffe95f4348c3db5 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1625,6 +1625,8 @@ struct super_operations {
        int (*unfreeze_fs) (struct super_block *);
        int (*statfs) (struct dentry *, struct kstatfs *);
        int (*remount_fs) (struct super_block *, int *, char *);
+       void *(*clone_mnt_data) (void *);
+       void (*copy_mnt_data) (void *, void *);
        void (*umount_begin) (struct super_block *);
 
        int (*show_options)(struct seq_file *, struct dentry *);
@@ -1835,6 +1837,7 @@ struct file_system_type {
 #define FS_RENAME_DOES_D_MOVE  32768   /* FS will handle d_move() during rename() internally. */
        struct dentry *(*mount) (struct file_system_type *, int,
                       const char *, void *);
+       void *(*alloc_mnt_data) (void);
        void (*kill_sb) (struct super_block *);
        struct module *owner;
        struct file_system_type * next;

diff --git a/include/linux/mount.h b/include/linux/mount.h
index 8eeb8f6ab1101e6ba9ab5d8742e3f96c00480fc7..64d6f21bd83b19a8cafa0547806bf9d4be275fd9 100644 (file)
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -60,6 +60,7 @@ struct vfsmount {
        struct dentry *mnt_root;        /* root of the mounted tree */
        struct super_block *mnt_sb;     /* pointer to superblock */
        int mnt_flags;
+       void *data;
 };
 
 struct file; /* forward dec */