diff options
Diffstat (limited to 'fs/afs/flock.c')
| -rw-r--r-- | fs/afs/flock.c | 559 |
1 files changed, 559 insertions, 0 deletions
diff --git a/fs/afs/flock.c b/fs/afs/flock.c new file mode 100644 index 00000000000..4f77f3caee9 --- /dev/null +++ b/fs/afs/flock.c @@ -0,0 +1,559 @@ +/* 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 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) +{ + if (!afs_lock_manager) { + afs_lock_manager = create_singlethread_workqueue("kafs_lockd"); + if (!afs_lock_manager) + return -ENOMEM; + } + return 0; +} + +/* + * 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); +} + +/* + * 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) + list_move_tail(&fl->fl_u.afs.link, + &vnode->granted_locks); + 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 (list_empty(&vnode->pending_locks)) { + /* 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->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: + goto acquired_server_lock; + case -EWOULDBLOCK: + 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; + } + } + + /* if we've already got a readlock on the server and no waiting + * writelocks, then we might be able to instantly grant another + * 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; + } + } + + /* 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 ((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); +} |