Subversion Repositories or1k_soc_on_altera_embedded_dev_kit

/* 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);

}