Re: [PATCH] AFS: Implement file locking

J. Bruce Fields
2007-05-26T02:23:56Z

On Thu, May 24, 2007 at 05:55:54PM +0100, David Howells wrote:
> +/*
> + * initialise the lock manager thread if it isn't already running
> + */
> +static int afs_init_lock_manager(void)
> +{
> + if (!afs_lock_manager) {
> + afs_lock_manager = create_singlethread_workqueue("kafs_lockd");
> + if (!afs_lock_manager)
> + return -ENOMEM;
> + }
> + return 0;

Doesn't this need some locking?

> +/*
> + * request a lock on a file on the server
> + */
> +static int afs_do_setlk(struct file *file, struct file_lock *fl)
> +{
> + struct afs_vnode *vnode = AFS_FS_I(file->f_mapping->host);
> + afs_lock_type_t type;
> + struct key *key = file->private_data;
> + int ret;
> +
> + _enter("{%x:%u},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type);
> +
> + /* only whole-file locks are supported */
> + if (fl->fl_start != 0 || fl->fl_end != OFFSET_MAX)
> + return -EINVAL;

Do you allow upgrades and downgrades? (Just curious.)

> + /* if we've already got a readlock on the server and no waiting
> + * writelocks, then we might be able to instantly grant another

Is that comment correct? (You don't really test for "waiting
writelocks", do you?)

> + * readlock */
> + if (type == AFS_LOCK_READ &&
> + vnode->flags & (1 << AFS_VNODE_READLOCKED)) {
> + _debug("instant readlock");
> + ASSERTCMP(vnode->flags &
> + ((1 << AFS_VNODE_LOCKING) |
> + (1 << AFS_VNODE_WRITELOCKED)), ==, 0);
> + ASSERT(!list_empty(&vnode->granted_locks));
> + goto sharing_existing_lock;
> + }
> + }

--b.