Commit 266eb3f2 authored by Greg Kurz's avatar Greg Kurz Committed by Miklos Szeredi
Browse files

fuse: Call vfs_get_tree() for submounts 



We recently fixed an infinite loop by setting the SB_BORN flag on
submounts along with the write barrier needed by super_cache_count().
This is the job of vfs_get_tree() and FUSE shouldn't have to care
about the barrier at all.

Split out some code from fuse_dentry_automount() to the dedicated
fuse_get_tree_submount() handler for submounts and call vfs_get_tree().

Signed-off-by: default avatarGreg Kurz <groug@kaod.org>
Reviewed-by: default avatarMax Reitz <mreitz@redhat.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent fe0a7bd8

fs/fuse/dir.c

+5 −48
Original line number Diff line number Diff line
@@ -309,12 +309,8 @@ static int fuse_dentry_delete(const struct dentry *dentry) 
static struct vfsmount *fuse_dentry_automount(struct path *path)

{

	struct fs_context *fsc;

	struct fuse_mount *parent_fm = get_fuse_mount_super(path->mnt->mnt_sb);

	struct fuse_conn *fc = parent_fm->fc;

	struct fuse_mount *fm;

	struct vfsmount *mnt;

	struct fuse_inode *mp_fi = get_fuse_inode(d_inode(path->dentry));

	struct super_block *sb;

	int err;



	fsc = fs_context_for_submount(path->mnt->mnt_sb->s_type, path->dentry);
@@ -323,48 +319,15 @@ static struct vfsmount *fuse_dentry_automount(struct path *path) 
		goto out;

	}



	err = -ENOMEM;

	fm = kzalloc(sizeof(struct fuse_mount), GFP_KERNEL);

	if (!fm)

		goto out_put_fsc;

	/* Pass the FUSE inode of the mount for fuse_get_tree_submount() */

	fsc->fs_private = mp_fi;



	fsc->s_fs_info = fm;

	sb = sget_fc(fsc, NULL, set_anon_super_fc);

	if (IS_ERR(sb)) {

		err = PTR_ERR(sb);

		kfree(fm);

	err = vfs_get_tree(fsc);

	if (err)

		goto out_put_fsc;

	}

	fm->fc = fuse_conn_get(fc);



	/* Initialize superblock, making @mp_fi its root */

	err = fuse_fill_super_submount(sb, mp_fi);

	if (err) {

		fuse_conn_put(fc);

		kfree(fm);

		sb->s_fs_info = NULL;

		goto out_put_sb;

	}



	down_write(&fc->killsb);

	list_add_tail(&fm->fc_entry, &fc->mounts);

	up_write(&fc->killsb);



	sb->s_flags |= SB_ACTIVE;

	fsc->root = dget(sb->s_root);



	/*

	 * FIXME: setting SB_BORN requires a write barrier for

	 *        super_cache_count(). We should actually come

	 *        up with a proper ->get_tree() implementation

	 *        for submounts and call vfs_get_tree() to take

	 *        care of the write barrier.

	 */

	smp_wmb();

	sb->s_flags |= SB_BORN;



	/* We are done configuring the superblock, so unlock it */

	up_write(&sb->s_umount);

	up_write(&fsc->root->d_sb->s_umount);



	/* Create the submount */

	mnt = vfs_create_mount(fsc);
@@ -376,12 +339,6 @@ static struct vfsmount *fuse_dentry_automount(struct path *path) 
	put_fs_context(fsc);

	return mnt;



out_put_sb:

	/*

	 * Only jump here when fsc->root is NULL and sb is still locked

	 * (otherwise put_fs_context() will put the superblock)

	 */

	deactivate_locked_super(sb);

out_put_fsc:

	put_fs_context(fsc);

out:

fs/fuse/inode.c

+36 −0
Original line number Diff line number Diff line
@@ -1353,8 +1353,44 @@ int fuse_fill_super_submount(struct super_block *sb, 
	return 0;

}



/* Filesystem context private data holds the FUSE inode of the mount point */

static int fuse_get_tree_submount(struct fs_context *fsc)

{

	struct fuse_mount *fm;

	struct fuse_inode *mp_fi = fsc->fs_private;

	struct fuse_conn *fc = get_fuse_conn(&mp_fi->inode);

	struct super_block *sb;

	int err;



	fm = kzalloc(sizeof(struct fuse_mount), GFP_KERNEL);

	if (!fm)

		return -ENOMEM;



	fsc->s_fs_info = fm;

	sb = sget_fc(fsc, NULL, set_anon_super_fc);

	if (IS_ERR(sb)) {

		kfree(fm);

		return PTR_ERR(sb);

	}

	fm->fc = fuse_conn_get(fc);



	/* Initialize superblock, making @mp_fi its root */

	err = fuse_fill_super_submount(sb, mp_fi);

	if (err) {

		fuse_conn_put(fc);

		kfree(fm);

		sb->s_fs_info = NULL;

		deactivate_locked_super(sb);

		return err;

	}



	down_write(&fc->killsb);

	list_add_tail(&fm->fc_entry, &fc->mounts);

	up_write(&fc->killsb);



	sb->s_flags |= SB_ACTIVE;

	fsc->root = dget(sb->s_root);



	return 0;

}