/*
 * Copyright (c) 2002, 2007 Red Hat, Inc. All rights reserved.
 *
 * This software may be freely redistributed under the terms of the
 * GNU General Public License.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * Authors: David Woodhouse <dwmw2@infradead.org>
 *          David Howells <dhowells@redhat.com>
 *
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/circ_buf.h>
#include <linux/sched.h>
#include "internal.h"

/*
 * Set up an interest-in-callbacks record for a volume on a server and
 * register it with the server.
 * - Called with vnode->io_lock held.
 */
int afs_register_server_cb_interest(struct afs_vnode *vnode,
                                    struct afs_server_list *slist,
                                    unsigned int index)
{
        struct afs_server_entry *entry = &slist->servers[index];
        struct afs_cb_interest *cbi, *vcbi, *new, *old;
        struct afs_server *server = entry->server;

again:
        if (vnode->cb_interest &&
            likely(vnode->cb_interest == entry->cb_interest))
                return 0;

        read_lock(&slist->lock);
        cbi = afs_get_cb_interest(entry->cb_interest);
        read_unlock(&slist->lock);

        vcbi = vnode->cb_interest;
        if (vcbi) {
                if (vcbi == cbi) {
                        afs_put_cb_interest(afs_v2net(vnode), cbi);
                        return 0;
                }

                /* Use a new interest in the server list for the same server
                 * rather than an old one that's still attached to a vnode.
                 */
                if (cbi && vcbi->server == cbi->server) {
                        write_seqlock(&vnode->cb_lock);
                        old = vnode->cb_interest;
                        vnode->cb_interest = cbi;
                        write_sequnlock(&vnode->cb_lock);
                        afs_put_cb_interest(afs_v2net(vnode), old);
                        return 0;
                }

                /* Re-use the one attached to the vnode. */
                if (!cbi && vcbi->server == server) {
                        write_lock(&slist->lock);
                        if (entry->cb_interest) {
                                write_unlock(&slist->lock);
                                afs_put_cb_interest(afs_v2net(vnode), cbi);
                                goto again;
                        }

                        entry->cb_interest = cbi;
                        write_unlock(&slist->lock);
                        return 0;
                }
        }

        if (!cbi) {
                new = kzalloc(sizeof(struct afs_cb_interest), GFP_KERNEL);
                if (!new)
                        return -ENOMEM;

                refcount_set(&new->usage, 1);
                new->sb = vnode->vfs_inode.i_sb;
                new->vid = vnode->volume->vid;
                new->server = afs_get_server(server);
                INIT_LIST_HEAD(&new->cb_link);

                write_lock(&server->cb_break_lock);
                list_add_tail(&new->cb_link, &server->cb_interests);
                write_unlock(&server->cb_break_lock);

                write_lock(&slist->lock);
                if (!entry->cb_interest) {
                        entry->cb_interest = afs_get_cb_interest(new);
                        cbi = new;
                        new = NULL;
                } else {
                        cbi = afs_get_cb_interest(entry->cb_interest);
                }
                write_unlock(&slist->lock);
                afs_put_cb_interest(afs_v2net(vnode), new);
        }

        ASSERT(cbi);

        /* Change the server the vnode is using.  This entails scrubbing any
         * interest the vnode had in the previous server it was using.
         */
        write_seqlock(&vnode->cb_lock);

        old = vnode->cb_interest;
        vnode->cb_interest = cbi;
        vnode->cb_s_break = cbi->server->cb_s_break;
        vnode->cb_v_break = vnode->volume->cb_v_break;
        clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);

        write_sequnlock(&vnode->cb_lock);
        afs_put_cb_interest(afs_v2net(vnode), old);
        return 0;
}

/*
 * Remove an interest on a server.
 */
void afs_put_cb_interest(struct afs_net *net, struct afs_cb_interest *cbi)
{
        if (cbi && refcount_dec_and_test(&cbi->usage)) {
                if (!list_empty(&cbi->cb_link)) {
                        write_lock(&cbi->server->cb_break_lock);
                        list_del_init(&cbi->cb_link);
                        write_unlock(&cbi->server->cb_break_lock);
                        afs_put_server(net, cbi->server);
                }
                kfree(cbi);
        }
}

/*
 * allow the fileserver to request callback state (re-)initialisation
 */
void afs_init_callback_state(struct afs_server *server)
{
        if (!test_and_clear_bit(AFS_SERVER_FL_NEW, &server->flags))
                server->cb_s_break++;
}

/*
 * actually break a callback
 */
void afs_break_callback(struct afs_vnode *vnode)
{
        _enter("");

        write_seqlock(&vnode->cb_lock);

        clear_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags);
        if (test_and_clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags)) {
                vnode->cb_break++;
                afs_clear_permits(vnode);

                spin_lock(&vnode->lock);

                _debug("break callback");

                if (list_empty(&vnode->granted_locks) &&
                    !list_empty(&vnode->pending_locks))
                        afs_lock_may_be_available(vnode);
                spin_unlock(&vnode->lock);
        }

        write_sequnlock(&vnode->cb_lock);
}

/*
 * allow the fileserver to explicitly break one callback
 * - happens when
 *   - the backing file is changed
 *   - a lock is released
 */
static void afs_break_one_callback(struct afs_server *server,
                                   struct afs_fid *fid)
{
        struct afs_cb_interest *cbi;
        struct afs_iget_data data;
        struct afs_vnode *vnode;
        struct inode *inode;

        read_lock(&server->cb_break_lock);

        /* Step through all interested superblocks.  There may be more than one
         * because of cell aliasing.
         */
        list_for_each_entry(cbi, &server->cb_interests, cb_link) {
                if (cbi->vid != fid->vid)
                        continue;

                if (fid->vnode == 0 && fid->unique == 0) {
                        /* The callback break applies to an entire volume. */
                        struct afs_super_info *as = AFS_FS_S(cbi->sb);
                        struct afs_volume *volume = as->volume;

                        write_lock(&volume->cb_break_lock);
                        volume->cb_v_break++;
                        write_unlock(&volume->cb_break_lock);
                } else {
                        data.volume = NULL;
                        data.fid = *fid;
                        inode = ilookup5_nowait(cbi->sb, fid->vnode,
                                                afs_iget5_test, &data);
                        if (inode) {
                                vnode = AFS_FS_I(inode);
                                afs_break_callback(vnode);
                                iput(inode);
                        }
                }
        }

        read_unlock(&server->cb_break_lock);
}

/*
 * allow the fileserver to break callback promises
 */
void afs_break_callbacks(struct afs_server *server, size_t count,
                         struct afs_callback_break *callbacks)
{
        _enter("%p,%zu,", server, count);

        ASSERT(server != NULL);
        ASSERTCMP(count, <=, AFSCBMAX);

        /* TODO: Sort the callback break list by volume ID */

        for (; count > 0; callbacks++, count--) {
                _debug("- Fid { vl=%08x n=%u u=%u }  CB { v=%u x=%u t=%u }",
                       callbacks->fid.vid,
                       callbacks->fid.vnode,
                       callbacks->fid.unique,
                       callbacks->cb.version,
                       callbacks->cb.expiry,
                       callbacks->cb.type
                       );
                afs_break_one_callback(server, &callbacks->fid);
        }

        _leave("");
        return;
}

/*
 * Clear the callback interests in a server list.
 */
void afs_clear_callback_interests(struct afs_net *net, struct afs_server_list *slist)
{
        int i;

        for (i = 0; i < slist->nr_servers; i++) {
                afs_put_cb_interest(net, slist->servers[i].cb_interest);
                slist->servers[i].cb_interest = NULL;
        }
}