ANDROID: 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 d18deb4c410b24ed276c9b60c869f4c06b6ec20f..247d1ca13be105dbbe2091104ab3304e4ab838e0 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -226,6 +226,7 @@ static struct mount *alloc_vfsmnt(const char *name)
                mnt->mnt_count = 1;
                mnt->mnt_writers = 0;
 #endif
+               mnt->mnt.data = NULL;
 
                INIT_HLIST_NODE(&mnt->mnt_hash);
                INIT_LIST_HEAD(&mnt->mnt_child);
@@ -637,6 +638,7 @@ int sb_prepare_remount_readonly(struct super_block *sb)
 
 static void free_vfsmnt(struct mount *mnt)
 {
+       kfree(mnt->mnt.data);
        kfree_const(mnt->mnt_devname);
 #ifdef CONFIG_SMP
        free_percpu(mnt->mnt_pcp);
@@ -1031,6 +1033,14 @@ vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void
        if (!mnt)
                return ERR_PTR(-ENOMEM);
 
+       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 & SB_KERNMOUNT)
                mnt->mnt.mnt_flags = MNT_INTERNAL;
 
@@ -1078,6 +1088,14 @@ 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
@@ -2329,8 +2347,14 @@ static int do_remount(struct path *path, int ms_flags, int sb_flags,
                err = change_mount_flags(path->mnt, ms_flags);
        else if (!capable(CAP_SYS_ADMIN))
                err = -EPERM;
-       else
+       else {
                err = do_remount_sb(sb, sb_flags, data, 0);
+               namespace_lock();
+               lock_mount_hash();
+               propagate_remount(mnt);
+               unlock_mount_hash();
+               namespace_unlock();
+       }
        if (!err) {
                lock_mount_hash();
                mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;

diff --git a/fs/pnode.c b/fs/pnode.c
index 53d411a371ce8d7efd060ee3e9ad37053a54e4ab..386884dd6d97c8fd5674a0eae378205d8d3b43f1 100644 (file)
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -607,3 +607,32 @@ int propagate_umount(struct list_head *list)
 
        return 0;
 }
+
+/*
+ *  Iterates over all slaves, and slaves of slaves.
+ */
+static struct mount *next_descendent(struct mount *root, struct mount *cur)
+{
+       if (!IS_MNT_NEW(cur) && !list_empty(&cur->mnt_slave_list))
+               return first_slave(cur);
+       do {
+               if (cur->mnt_slave.next != &cur->mnt_master->mnt_slave_list)
+                       return next_slave(cur);
+               cur = cur->mnt_master;
+       } while (cur != root);
+       return NULL;
+}
+
+void propagate_remount(struct mount *mnt)
+{
+       struct mount *m = mnt;
+       struct super_block *sb = mnt->mnt.mnt_sb;
+
+       if (sb->s_op->copy_mnt_data) {
+               m = next_descendent(mnt, m);
+               while (m) {
+                       sb->s_op->copy_mnt_data(m->mnt.data, mnt->mnt.data);
+                       m = next_descendent(mnt, m);
+               }
+       }
+}

diff --git a/fs/pnode.h b/fs/pnode.h
index dc87e65becd21eb0235775fedf28d8a21702f548..a9a6576540addb55510a41df67cce73339460208 100644 (file)
--- a/fs/pnode.h
+++ b/fs/pnode.h
@@ -44,6 +44,7 @@ int propagate_mnt(struct mount *, struct mountpoint *, struct mount *,
 int propagate_umount(struct list_head *);
 int propagate_mount_busy(struct mount *, int);
 void propagate_mount_unlock(struct mount *);
+void 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 ef0fc9ab6876d73097ccc2fcb5e3a6d7fd7ac246..905bd2e9e4baf7390b7547e347097668a8a675ae 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1815,6 +1815,8 @@ 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 *);
@@ -2077,6 +2079,7 @@ 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 45b1f56c6c2f9fb0db10fc912251955af04fc05e..1ff21c19b0b9f9e8c6d6ef182bc1829f6f04a4be 100644 (file)
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -68,6 +68,7 @@ struct vfsmount {
        struct dentry *mnt_root;        /* root of the mounted tree */
        struct super_block *mnt_sb;     /* pointer to superblock */
        int mnt_flags;
+       void *data;
 } __randomize_layout;
 
 struct file; /* forward dec */