/* AFS file locking support * * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. */ #include <linux/smp_lock.h> #include "internal.h" #define AFS_LOCK_GRANTED 0 #define AFS_LOCK_PENDING 1 static void afs_fl_copy_lock(struct file_lock *new, struct file_lock *fl); static void afs_fl_release_private(struct file_lock *fl); static struct workqueue_struct *afs_lock_manager; static DEFINE_MUTEX(afs_lock_manager_mutex); static struct file_lock_operations afs_lock_ops = { .fl_copy_lock = afs_fl_copy_lock, .fl_release_private = afs_fl_release_private, }; /* * initialise the lock manager thread if it isn't already running */ static int afs_init_lock_manager(void) { int ret; ret = 0; if (!afs_lock_manager) { mutex_lock(&afs_lock_manager_mutex); if (!afs_lock_manager) { afs_lock_manager = create_singlethread_workqueue("kafs_lockd"); if (!afs_lock_manager) ret = -ENOMEM; } mutex_unlock(&afs_lock_manager_mutex); } return ret; } /* * destroy the lock manager thread if it's running */ void __exit afs_kill_lock_manager(void) { if (afs_lock_manager) destroy_workqueue(afs_lock_manager); } /* * if the callback is broken on this vnode, then the lock may now be available */ void afs_lock_may_be_available(struct afs_vnode *vnode) { _enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode); queue_delayed_work(afs_lock_manager, &vnode->lock_work, 0); } /* * the lock will time out in 5 minutes unless we extend it, so schedule * extension in a bit less than that time */ static void afs_schedule_lock_extension(struct afs_vnode *vnode) { queue_delayed_work(afs_lock_manager, &vnode->lock_work, AFS_LOCKWAIT * HZ / 2); } /* * grant one or more locks (readlocks are allowed to jump the queue if the * first lock in the queue is itself a readlock) * - the caller must hold the vnode lock */ static void afs_grant_locks(struct afs_vnode *vnode, struct file_lock *fl) { struct file_lock *p, *_p; list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks); if (fl->fl_type == F_RDLCK) { list_for_each_entry_safe(p, _p, &vnode->pending_locks, fl_u.afs.link) { if (p->fl_type == F_RDLCK) { p->fl_u.afs.state = AFS_LOCK_GRANTED; list_move_tail(&p->fl_u.afs.link, &vnode->granted_locks); wake_up(&p->fl_wait); } } } } /* * do work for a lock, including: * - probing for a lock we're waiting on but didn't get immediately * - extending a lock that's close to timing out */ void afs_lock_work(struct work_struct *work) { struct afs_vnode *vnode = container_of(work, struct afs_vnode, lock_work.work); struct file_lock *fl; afs_lock_type_t type; struct key *key; int ret; _enter("{%x:%u}", vnode->fid.vid, vnode->fid.vnode); spin_lock(&vnode->lock); if (test_bit(AFS_VNODE_UNLOCKING, &vnode->flags)) { _debug("unlock"); spin_unlock(&vnode->lock); /* attempt to release the server lock; if it fails, we just * wait 5 minutes and it'll time out anyway */ ret = afs_vnode_release_lock(vnode, vnode->unlock_key); if (ret < 0) printk(KERN_WARNING "AFS:" " Failed to release lock on {%x:%x} error %d\n", vnode->fid.vid, vnode->fid.vnode, ret); spin_lock(&vnode->lock); key_put(vnode->unlock_key); vnode->unlock_key = NULL; clear_bit(AFS_VNODE_UNLOCKING, &vnode->flags); } /* if we've got a lock, then it must be time to extend that lock as AFS * locks time out after 5 minutes */ if (!list_empty(&vnode->granted_locks)) { _debug("extend"); if (test_and_set_bit(AFS_VNODE_LOCKING, &vnode->flags)) BUG(); fl = list_entry(vnode->granted_locks.next, struct file_lock, fl_u.afs.link); key = key_get(fl->fl_file->private_data); spin_unlock(&vnode->lock); ret = afs_vnode_extend_lock(vnode, key); clear_bit(AFS_VNODE_LOCKING, &vnode->flags); key_put(key); switch (ret) { case 0: afs_schedule_lock_extension(vnode); break; default: /* ummm... we failed to extend the lock - retry * extension shortly */ printk(KERN_WARNING "AFS:" " Failed to extend lock on {%x:%x} error %d\n", vnode->fid.vid, vnode->fid.vnode, ret); queue_delayed_work(afs_lock_manager, &vnode->lock_work, HZ * 10); break; } _leave(" [extend]"); return; } /* if we don't have a granted lock, then we must've been called back by * the server, and so if might be possible to get a lock we're * currently waiting for */ if (!list_empty(&vnode->pending_locks)) { _debug("get"); if (test_and_set_bit(AFS_VNODE_LOCKING, &vnode->flags)) BUG(); fl = list_entry(vnode->pending_locks.next, struct file_lock, fl_u.afs.link); key = key_get(fl->fl_file->private_data); type = (fl->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE; spin_unlock(&vnode->lock); ret = afs_vnode_set_lock(vnode, key, type); clear_bit(AFS_VNODE_LOCKING, &vnode->flags); switch (ret) { case -EWOULDBLOCK: _debug("blocked"); break; case 0: _debug("acquired"); if (type == AFS_LOCK_READ) set_bit(AFS_VNODE_READLOCKED, &vnode->flags); else set_bit(AFS_VNODE_WRITELOCKED, &vnode->flags); ret = AFS_LOCK_GRANTED; default: spin_lock(&vnode->lock); /* the pending lock may have been withdrawn due to a * signal */ if (list_entry(vnode->pending_locks.next, struct file_lock, fl_u.afs.link) == fl) { fl->fl_u.afs.state = ret; if (ret == AFS_LOCK_GRANTED) afs_grant_locks(vnode, fl); else list_del_init(&fl->fl_u.afs.link); wake_up(&fl->fl_wait); spin_unlock(&vnode->lock); } else { _debug("withdrawn"); clear_bit(AFS_VNODE_READLOCKED, &vnode->flags); clear_bit(AFS_VNODE_WRITELOCKED, &vnode->flags); spin_unlock(&vnode->lock); afs_vnode_release_lock(vnode, key); if (!list_empty(&vnode->pending_locks)) afs_lock_may_be_available(vnode); } break; } key_put(key); _leave(" [pend]"); return; } /* looks like the lock request was withdrawn on a signal */ spin_unlock(&vnode->lock); _leave(" [no locks]"); } /* * pass responsibility for the unlocking of a vnode on the server to the * manager thread, lest a pending signal in the calling thread interrupt * AF_RXRPC * - the caller must hold the vnode lock */ static void afs_defer_unlock(struct afs_vnode *vnode, struct key *key) { cancel_delayed_work(&vnode->lock_work); if (!test_and_clear_bit(AFS_VNODE_READLOCKED, &vnode->flags) && !test_and_clear_bit(AFS_VNODE_WRITELOCKED, &vnode->flags)) BUG(); if (test_and_set_bit(AFS_VNODE_UNLOCKING, &vnode->flags)) BUG(); vnode->unlock_key = key_get(key); afs_lock_may_be_available(vnode); } /* * 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; ret = afs_init_lock_manager(); if (ret < 0) return ret; fl->fl_ops = &afs_lock_ops; INIT_LIST_HEAD(&fl->fl_u.afs.link); fl->fl_u.afs.state = AFS_LOCK_PENDING; type = (fl->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE; lock_kernel(); /* make sure we've got a callback on this file and that our view of the * data version is up to date */ ret = afs_vnode_fetch_status(vnode, NULL, key); if (ret < 0) goto error; if (vnode->status.lock_count != 0 && !(fl->fl_flags & FL_SLEEP)) { ret = -EAGAIN; goto error; } spin_lock(&vnode->lock); /* if we've already got a readlock on the server then we can instantly * grant another readlock, irrespective of whether there are any * pending writelocks */ 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; } /* if there's no-one else with a lock on this vnode, then we need to * ask the server for a lock */ if (list_empty(&vnode->pending_locks) && list_empty(&vnode->granted_locks)) { _debug("not locked"); ASSERTCMP(vnode->flags & ((1 << AFS_VNODE_LOCKING) | (1 << AFS_VNODE_READLOCKED) | (1 << AFS_VNODE_WRITELOCKED)), ==, 0); list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks); set_bit(AFS_VNODE_LOCKING, &vnode->flags); spin_unlock(&vnode->lock); ret = afs_vnode_set_lock(vnode, key, type); clear_bit(AFS_VNODE_LOCKING, &vnode->flags); switch (ret) { case 0: _debug("acquired"); goto acquired_server_lock; case -EWOULDBLOCK: _debug("would block"); spin_lock(&vnode->lock); ASSERT(list_empty(&vnode->granted_locks)); ASSERTCMP(vnode->pending_locks.next, ==, &fl->fl_u.afs.link); goto wait; default: spin_lock(&vnode->lock); list_del_init(&fl->fl_u.afs.link); spin_unlock(&vnode->lock); goto error; } } /* otherwise, we need to wait for a local lock to become available */ _debug("wait local"); list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks); wait: if (!(fl->fl_flags & FL_SLEEP)) { _debug("noblock"); ret = -EAGAIN; goto abort_attempt; } spin_unlock(&vnode->lock); /* now we need to sleep and wait for the lock manager thread to get the * lock from the server */ _debug("sleep"); ret = wait_event_interruptible(fl->fl_wait, fl->fl_u.afs.state <= AFS_LOCK_GRANTED); if (fl->fl_u.afs.state <= AFS_LOCK_GRANTED) { ret = fl->fl_u.afs.state; if (ret < 0) goto error; spin_lock(&vnode->lock); goto given_lock; } /* we were interrupted, but someone may still be in the throes of * giving us the lock */ _debug("intr"); ASSERTCMP(ret, ==, -ERESTARTSYS); spin_lock(&vnode->lock); if (fl->fl_u.afs.state <= AFS_LOCK_GRANTED) { ret = fl->fl_u.afs.state; if (ret < 0) { spin_unlock(&vnode->lock); goto error; } goto given_lock; } abort_attempt: /* we aren't going to get the lock, either because we're unwilling to * wait, or because some signal happened */ _debug("abort"); if (list_empty(&vnode->granted_locks) && vnode->pending_locks.next == &fl->fl_u.afs.link) { if (vnode->pending_locks.prev != &fl->fl_u.afs.link) { /* kick the next pending lock into having a go */ list_del_init(&fl->fl_u.afs.link); afs_lock_may_be_available(vnode); } } else { list_del_init(&fl->fl_u.afs.link); } spin_unlock(&vnode->lock); goto error; acquired_server_lock: /* we've acquired a server lock, but it needs to be renewed after 5 * mins */ spin_lock(&vnode->lock); afs_schedule_lock_extension(vnode); if (type == AFS_LOCK_READ) set_bit(AFS_VNODE_READLOCKED, &vnode->flags); else set_bit(AFS_VNODE_WRITELOCKED, &vnode->flags); sharing_existing_lock: /* the lock has been granted as far as we're concerned... */ fl->fl_u.afs.state = AFS_LOCK_GRANTED; list_move_tail(&fl->fl_u.afs.link, &vnode->granted_locks); given_lock: /* ... but we do still need to get the VFS's blessing */ ASSERT(!(vnode->flags & (1 << AFS_VNODE_LOCKING))); ASSERT((vnode->flags & ((1 << AFS_VNODE_READLOCKED) | (1 << AFS_VNODE_WRITELOCKED))) != 0); ret = posix_lock_file(file, fl, NULL); if (ret < 0) goto vfs_rejected_lock; spin_unlock(&vnode->lock); /* again, make sure we've got a callback on this file and, again, make * sure that our view of the data version is up to date (we ignore * errors incurred here and deal with the consequences elsewhere) */ afs_vnode_fetch_status(vnode, NULL, key); error: unlock_kernel(); _leave(" = %d", ret); return ret; vfs_rejected_lock: /* the VFS rejected the lock we just obtained, so we have to discard * what we just got */ _debug("vfs refused %d", ret); list_del_init(&fl->fl_u.afs.link); if (list_empty(&vnode->granted_locks)) afs_defer_unlock(vnode, key); spin_unlock(&vnode->lock); goto abort_attempt; } /* * 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; posix_test_lock(file, fl); if (fl->fl_type == F_UNLCK) { /* 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 (__mandatory_lock(&vnode->vfs_inode) && 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); }