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559 lines
15 KiB
C
559 lines
15 KiB
C
![]() |
/* AFS file locking support
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*
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* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/smp_lock.h>
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#include "internal.h"
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#define AFS_LOCK_GRANTED 0
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#define AFS_LOCK_PENDING 1
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static void afs_fl_copy_lock(struct file_lock *new, struct file_lock *fl);
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static void afs_fl_release_private(struct file_lock *fl);
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static struct workqueue_struct *afs_lock_manager;
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static struct file_lock_operations afs_lock_ops = {
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.fl_copy_lock = afs_fl_copy_lock,
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.fl_release_private = afs_fl_release_private,
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};
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/*
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* initialise the lock manager thread if it isn't already running
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*/
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static int afs_init_lock_manager(void)
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{
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if (!afs_lock_manager) {
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afs_lock_manager = create_singlethread_workqueue("kafs_lockd");
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if (!afs_lock_manager)
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return -ENOMEM;
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}
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return 0;
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}
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/*
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* destroy the lock manager thread if it's running
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*/
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void __exit afs_kill_lock_manager(void)
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{
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if (afs_lock_manager)
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destroy_workqueue(afs_lock_manager);
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}
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/*
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* if the callback is broken on this vnode, then the lock may now be available
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*/
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void afs_lock_may_be_available(struct afs_vnode *vnode)
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{
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_enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
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queue_delayed_work(afs_lock_manager, &vnode->lock_work, 0);
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}
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/*
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* the lock will time out in 5 minutes unless we extend it, so schedule
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* extension in a bit less than that time
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*/
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static void afs_schedule_lock_extension(struct afs_vnode *vnode)
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{
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queue_delayed_work(afs_lock_manager, &vnode->lock_work,
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AFS_LOCKWAIT * HZ / 2);
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}
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/*
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* do work for a lock, including:
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* - probing for a lock we're waiting on but didn't get immediately
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* - extending a lock that's close to timing out
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*/
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void afs_lock_work(struct work_struct *work)
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{
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struct afs_vnode *vnode =
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container_of(work, struct afs_vnode, lock_work.work);
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struct file_lock *fl;
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afs_lock_type_t type;
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struct key *key;
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int ret;
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_enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode);
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spin_lock(&vnode->lock);
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if (test_bit(AFS_VNODE_UNLOCKING, &vnode->flags)) {
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_debug("unlock");
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spin_unlock(&vnode->lock);
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/* attempt to release the server lock; if it fails, we just
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* wait 5 minutes and it'll time out anyway */
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ret = afs_vnode_release_lock(vnode, vnode->unlock_key);
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if (ret < 0)
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printk(KERN_WARNING "AFS:"
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" Failed to release lock on {%x:%x} error %d\n",
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vnode->fid.vid, vnode->fid.vnode, ret);
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spin_lock(&vnode->lock);
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key_put(vnode->unlock_key);
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vnode->unlock_key = NULL;
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clear_bit(AFS_VNODE_UNLOCKING, &vnode->flags);
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}
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/* if we've got a lock, then it must be time to extend that lock as AFS
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* locks time out after 5 minutes */
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if (!list_empty(&vnode->granted_locks)) {
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_debug("extend");
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if (test_and_set_bit(AFS_VNODE_LOCKING, &vnode->flags))
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BUG();
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fl = list_entry(vnode->granted_locks.next,
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struct file_lock, fl_u.afs.link);
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key = key_get(fl->fl_file->private_data);
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spin_unlock(&vnode->lock);
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ret = afs_vnode_extend_lock(vnode, key);
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clear_bit(AFS_VNODE_LOCKING, &vnode->flags);
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key_put(key);
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switch (ret) {
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case 0:
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afs_schedule_lock_extension(vnode);
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break;
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default:
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/* ummm... we failed to extend the lock - retry
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* extension shortly */
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printk(KERN_WARNING "AFS:"
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" Failed to extend lock on {%x:%x} error %d\n",
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vnode->fid.vid, vnode->fid.vnode, ret);
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queue_delayed_work(afs_lock_manager, &vnode->lock_work,
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HZ * 10);
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break;
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}
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_leave(" [extend]");
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return;
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}
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/* if we don't have a granted lock, then we must've been called back by
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* the server, and so if might be possible to get a lock we're
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* currently waiting for */
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if (!list_empty(&vnode->pending_locks)) {
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_debug("get");
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if (test_and_set_bit(AFS_VNODE_LOCKING, &vnode->flags))
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BUG();
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fl = list_entry(vnode->pending_locks.next,
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struct file_lock, fl_u.afs.link);
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key = key_get(fl->fl_file->private_data);
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type = (fl->fl_type == F_RDLCK) ?
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AFS_LOCK_READ : AFS_LOCK_WRITE;
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spin_unlock(&vnode->lock);
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ret = afs_vnode_set_lock(vnode, key, type);
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clear_bit(AFS_VNODE_LOCKING, &vnode->flags);
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switch (ret) {
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case -EWOULDBLOCK:
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_debug("blocked");
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break;
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case 0:
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_debug("acquired");
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if (type == AFS_LOCK_READ)
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set_bit(AFS_VNODE_READLOCKED, &vnode->flags);
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else
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set_bit(AFS_VNODE_WRITELOCKED, &vnode->flags);
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ret = AFS_LOCK_GRANTED;
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default:
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spin_lock(&vnode->lock);
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/* the pending lock may have been withdrawn due to a
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* signal */
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if (list_entry(vnode->pending_locks.next,
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struct file_lock, fl_u.afs.link) == fl) {
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fl->fl_u.afs.state = ret;
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if (ret == AFS_LOCK_GRANTED)
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list_move_tail(&fl->fl_u.afs.link,
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&vnode->granted_locks);
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else
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list_del_init(&fl->fl_u.afs.link);
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wake_up(&fl->fl_wait);
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spin_unlock(&vnode->lock);
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} else {
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_debug("withdrawn");
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clear_bit(AFS_VNODE_READLOCKED, &vnode->flags);
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clear_bit(AFS_VNODE_WRITELOCKED, &vnode->flags);
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spin_unlock(&vnode->lock);
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afs_vnode_release_lock(vnode, key);
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if (!list_empty(&vnode->pending_locks))
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afs_lock_may_be_available(vnode);
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}
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break;
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}
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key_put(key);
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_leave(" [pend]");
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return;
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}
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/* looks like the lock request was withdrawn on a signal */
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spin_unlock(&vnode->lock);
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_leave(" [no locks]");
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}
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/*
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* pass responsibility for the unlocking of a vnode on the server to the
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* manager thread, lest a pending signal in the calling thread interrupt
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* AF_RXRPC
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* - the caller must hold the vnode lock
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*/
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static void afs_defer_unlock(struct afs_vnode *vnode, struct key *key)
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{
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cancel_delayed_work(&vnode->lock_work);
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if (!test_and_clear_bit(AFS_VNODE_READLOCKED, &vnode->flags) &&
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!test_and_clear_bit(AFS_VNODE_WRITELOCKED, &vnode->flags))
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BUG();
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if (test_and_set_bit(AFS_VNODE_UNLOCKING, &vnode->flags))
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BUG();
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vnode->unlock_key = key_get(key);
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afs_lock_may_be_available(vnode);
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}
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/*
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* request a lock on a file on the server
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*/
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static int afs_do_setlk(struct file *file, struct file_lock *fl)
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{
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struct afs_vnode *vnode = AFS_FS_I(file->f_mapping->host);
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afs_lock_type_t type;
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struct key *key = file->private_data;
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int ret;
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_enter("{%x:%u},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type);
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/* only whole-file locks are supported */
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if (fl->fl_start != 0 || fl->fl_end != OFFSET_MAX)
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return -EINVAL;
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ret = afs_init_lock_manager();
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if (ret < 0)
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return ret;
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fl->fl_ops = &afs_lock_ops;
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INIT_LIST_HEAD(&fl->fl_u.afs.link);
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fl->fl_u.afs.state = AFS_LOCK_PENDING;
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type = (fl->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE;
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lock_kernel();
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/* make sure we've got a callback on this file and that our view of the
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* data version is up to date */
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ret = afs_vnode_fetch_status(vnode, NULL, key);
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if (ret < 0)
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goto error;
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if (vnode->status.lock_count != 0 && !(fl->fl_flags & FL_SLEEP)) {
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ret = -EAGAIN;
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goto error;
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}
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spin_lock(&vnode->lock);
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if (list_empty(&vnode->pending_locks)) {
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/* if there's no-one else with a lock on this vnode, then we
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* need to ask the server for a lock */
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if (list_empty(&vnode->granted_locks)) {
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_debug("not locked");
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ASSERTCMP(vnode->flags &
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((1 << AFS_VNODE_LOCKING) |
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(1 << AFS_VNODE_READLOCKED) |
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(1 << AFS_VNODE_WRITELOCKED)), ==, 0);
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list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);
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set_bit(AFS_VNODE_LOCKING, &vnode->flags);
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spin_unlock(&vnode->lock);
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ret = afs_vnode_set_lock(vnode, key, type);
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clear_bit(AFS_VNODE_LOCKING, &vnode->flags);
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switch (ret) {
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case 0:
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goto acquired_server_lock;
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case -EWOULDBLOCK:
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spin_lock(&vnode->lock);
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ASSERT(list_empty(&vnode->granted_locks));
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ASSERTCMP(vnode->pending_locks.next, ==,
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&fl->fl_u.afs.link);
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goto wait;
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default:
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spin_lock(&vnode->lock);
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list_del_init(&fl->fl_u.afs.link);
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spin_unlock(&vnode->lock);
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goto error;
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}
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}
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/* if we've already got a readlock on the server and no waiting
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* writelocks, then we might be able to instantly grant another
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* readlock */
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if (type == AFS_LOCK_READ &&
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vnode->flags & (1 << AFS_VNODE_READLOCKED)) {
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_debug("instant readlock");
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ASSERTCMP(vnode->flags &
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((1 << AFS_VNODE_LOCKING) |
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(1 << AFS_VNODE_WRITELOCKED)), ==, 0);
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ASSERT(!list_empty(&vnode->granted_locks));
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goto sharing_existing_lock;
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}
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}
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/* otherwise, we need to wait for a local lock to become available */
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_debug("wait local");
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list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks);
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wait:
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if (!(fl->fl_flags & FL_SLEEP)) {
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_debug("noblock");
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ret = -EAGAIN;
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goto abort_attempt;
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}
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spin_unlock(&vnode->lock);
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/* now we need to sleep and wait for the lock manager thread to get the
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* lock from the server */
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_debug("sleep");
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ret = wait_event_interruptible(fl->fl_wait,
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fl->fl_u.afs.state <= AFS_LOCK_GRANTED);
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if (fl->fl_u.afs.state <= AFS_LOCK_GRANTED) {
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ret = fl->fl_u.afs.state;
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if (ret < 0)
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goto error;
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spin_lock(&vnode->lock);
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goto given_lock;
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}
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/* we were interrupted, but someone may still be in the throes of
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* giving us the lock */
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_debug("intr");
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ASSERTCMP(ret, ==, -ERESTARTSYS);
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spin_lock(&vnode->lock);
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if (fl->fl_u.afs.state <= AFS_LOCK_GRANTED) {
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ret = fl->fl_u.afs.state;
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if (ret < 0) {
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spin_unlock(&vnode->lock);
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goto error;
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}
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goto given_lock;
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}
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abort_attempt:
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/* we aren't going to get the lock, either because we're unwilling to
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* wait, or because some signal happened */
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_debug("abort");
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if (list_empty(&vnode->granted_locks) &&
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vnode->pending_locks.next == &fl->fl_u.afs.link) {
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if (vnode->pending_locks.prev != &fl->fl_u.afs.link) {
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/* kick the next pending lock into having a go */
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list_del_init(&fl->fl_u.afs.link);
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afs_lock_may_be_available(vnode);
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}
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} else {
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list_del_init(&fl->fl_u.afs.link);
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}
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spin_unlock(&vnode->lock);
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goto error;
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acquired_server_lock:
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/* we've acquired a server lock, but it needs to be renewed after 5
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* mins */
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spin_lock(&vnode->lock);
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afs_schedule_lock_extension(vnode);
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if (type == AFS_LOCK_READ)
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set_bit(AFS_VNODE_READLOCKED, &vnode->flags);
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else
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set_bit(AFS_VNODE_WRITELOCKED, &vnode->flags);
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sharing_existing_lock:
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/* the lock has been granted as far as we're concerned... */
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fl->fl_u.afs.state = AFS_LOCK_GRANTED;
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list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks);
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given_lock:
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/* ... but we do still need to get the VFS's blessing */
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ASSERT(!(vnode->flags & (1 << AFS_VNODE_LOCKING)));
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ASSERT((vnode->flags & ((1 << AFS_VNODE_READLOCKED) |
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(1 << AFS_VNODE_WRITELOCKED))) != 0);
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ret = posix_lock_file(file, fl, NULL);
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if (ret < 0)
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goto vfs_rejected_lock;
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spin_unlock(&vnode->lock);
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/* again, make sure we've got a callback on this file and, again, make
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* sure that our view of the data version is up to date (we ignore
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* errors incurred here and deal with the consequences elsewhere) */
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afs_vnode_fetch_status(vnode, NULL, key);
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error:
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unlock_kernel();
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_leave(" = %d", ret);
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return ret;
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vfs_rejected_lock:
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/* the VFS rejected the lock we just obtained, so we have to discard
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* what we just got */
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_debug("vfs refused %d", ret);
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list_del_init(&fl->fl_u.afs.link);
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if (list_empty(&vnode->granted_locks))
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afs_defer_unlock(vnode, key);
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spin_unlock(&vnode->lock);
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goto abort_attempt;
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}
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|
||
|
/*
|
||
|
* unlock on a file on the server
|
||
|
*/
|
||
|
static int afs_do_unlk(struct file *file, struct file_lock *fl)
|
||
|
{
|
||
|
struct afs_vnode *vnode = AFS_FS_I(file->f_mapping->host);
|
||
|
struct key *key = file->private_data;
|
||
|
int ret;
|
||
|
|
||
|
_enter("{%x:%u},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type);
|
||
|
|
||
|
/* only whole-file unlocks are supported */
|
||
|
if (fl->fl_start != 0 || fl->fl_end != OFFSET_MAX)
|
||
|
return -EINVAL;
|
||
|
|
||
|
fl->fl_ops = &afs_lock_ops;
|
||
|
INIT_LIST_HEAD(&fl->fl_u.afs.link);
|
||
|
fl->fl_u.afs.state = AFS_LOCK_PENDING;
|
||
|
|
||
|
spin_lock(&vnode->lock);
|
||
|
ret = posix_lock_file(file, fl, NULL);
|
||
|
if (ret < 0) {
|
||
|
spin_unlock(&vnode->lock);
|
||
|
_leave(" = %d [vfs]", ret);
|
||
|
return ret;
|
||
|
}
|
||
|
|
||
|
/* discard the server lock only if all granted locks are gone */
|
||
|
if (list_empty(&vnode->granted_locks))
|
||
|
afs_defer_unlock(vnode, key);
|
||
|
spin_unlock(&vnode->lock);
|
||
|
_leave(" = 0");
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* return information about a lock we currently hold, if indeed we hold one
|
||
|
*/
|
||
|
static int afs_do_getlk(struct file *file, struct file_lock *fl)
|
||
|
{
|
||
|
struct afs_vnode *vnode = AFS_FS_I(file->f_mapping->host);
|
||
|
struct key *key = file->private_data;
|
||
|
int ret, lock_count;
|
||
|
|
||
|
_enter("");
|
||
|
|
||
|
fl->fl_type = F_UNLCK;
|
||
|
|
||
|
mutex_lock(&vnode->vfs_inode.i_mutex);
|
||
|
|
||
|
/* check local lock records first */
|
||
|
ret = 0;
|
||
|
if (posix_test_lock(file, fl) == 0) {
|
||
|
/* no local locks; consult the server */
|
||
|
ret = afs_vnode_fetch_status(vnode, NULL, key);
|
||
|
if (ret < 0)
|
||
|
goto error;
|
||
|
lock_count = vnode->status.lock_count;
|
||
|
if (lock_count) {
|
||
|
if (lock_count > 0)
|
||
|
fl->fl_type = F_RDLCK;
|
||
|
else
|
||
|
fl->fl_type = F_WRLCK;
|
||
|
fl->fl_start = 0;
|
||
|
fl->fl_end = OFFSET_MAX;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
error:
|
||
|
mutex_unlock(&vnode->vfs_inode.i_mutex);
|
||
|
_leave(" = %d [%hd]", ret, fl->fl_type);
|
||
|
return ret;
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* manage POSIX locks on a file
|
||
|
*/
|
||
|
int afs_lock(struct file *file, int cmd, struct file_lock *fl)
|
||
|
{
|
||
|
struct afs_vnode *vnode = AFS_FS_I(file->f_dentry->d_inode);
|
||
|
|
||
|
_enter("{%x:%u},%d,{t=%x,fl=%x,r=%Ld:%Ld}",
|
||
|
vnode->fid.vid, vnode->fid.vnode, cmd,
|
||
|
fl->fl_type, fl->fl_flags,
|
||
|
(long long) fl->fl_start, (long long) fl->fl_end);
|
||
|
|
||
|
/* AFS doesn't support mandatory locks */
|
||
|
if ((vnode->vfs_inode.i_mode & (S_ISGID | S_IXGRP)) == S_ISGID &&
|
||
|
fl->fl_type != F_UNLCK)
|
||
|
return -ENOLCK;
|
||
|
|
||
|
if (IS_GETLK(cmd))
|
||
|
return afs_do_getlk(file, fl);
|
||
|
if (fl->fl_type == F_UNLCK)
|
||
|
return afs_do_unlk(file, fl);
|
||
|
return afs_do_setlk(file, fl);
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* manage FLOCK locks on a file
|
||
|
*/
|
||
|
int afs_flock(struct file *file, int cmd, struct file_lock *fl)
|
||
|
{
|
||
|
struct afs_vnode *vnode = AFS_FS_I(file->f_dentry->d_inode);
|
||
|
|
||
|
_enter("{%x:%u},%d,{t=%x,fl=%x}",
|
||
|
vnode->fid.vid, vnode->fid.vnode, cmd,
|
||
|
fl->fl_type, fl->fl_flags);
|
||
|
|
||
|
/*
|
||
|
* No BSD flocks over NFS allowed.
|
||
|
* Note: we could try to fake a POSIX lock request here by
|
||
|
* using ((u32) filp | 0x80000000) or some such as the pid.
|
||
|
* Not sure whether that would be unique, though, or whether
|
||
|
* that would break in other places.
|
||
|
*/
|
||
|
if (!(fl->fl_flags & FL_FLOCK))
|
||
|
return -ENOLCK;
|
||
|
|
||
|
/* we're simulating flock() locks using posix locks on the server */
|
||
|
fl->fl_owner = (fl_owner_t) file;
|
||
|
fl->fl_start = 0;
|
||
|
fl->fl_end = OFFSET_MAX;
|
||
|
|
||
|
if (fl->fl_type == F_UNLCK)
|
||
|
return afs_do_unlk(file, fl);
|
||
|
return afs_do_setlk(file, fl);
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* the POSIX lock management core VFS code copies the lock record and adds the
|
||
|
* copy into its own list, so we need to add that copy to the vnode's lock
|
||
|
* queue in the same place as the original (which will be deleted shortly
|
||
|
* after)
|
||
|
*/
|
||
|
static void afs_fl_copy_lock(struct file_lock *new, struct file_lock *fl)
|
||
|
{
|
||
|
_enter("");
|
||
|
|
||
|
list_add(&new->fl_u.afs.link, &fl->fl_u.afs.link);
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* need to remove this lock from the vnode queue when it's removed from the
|
||
|
* VFS's list
|
||
|
*/
|
||
|
static void afs_fl_release_private(struct file_lock *fl)
|
||
|
{
|
||
|
_enter("");
|
||
|
|
||
|
list_del_init(&fl->fl_u.afs.link);
|
||
|
}
|