// SPDX-License-Identifier: GPL-2.0-or-later
/* Fileserver-directed operation handling.
 *
 * Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include "internal.h"

static atomic_t afs_operation_debug_counter;

/*
 * Create an operation against a volume.
 */
struct afs_operation *afs_alloc_operation(struct key *key, struct afs_volume *volume)
{
        struct afs_operation *op;

        _enter("");

        op = kzalloc_obj(*op);
        if (!op)
                return ERR_PTR(-ENOMEM);

        if (!key) {
                key = afs_request_key(volume->cell);
                if (IS_ERR(key)) {
                        kfree(op);
                        return ERR_CAST(key);
                }
        } else {
                key_get(key);
        }

        op->key                 = key;
        op->volume              = afs_get_volume(volume, afs_volume_trace_get_new_op);
        op->net                 = volume->cell->net;
        op->cb_v_break          = atomic_read(&volume->cb_v_break);
        op->pre_volsync.creation = volume->creation_time;
        op->pre_volsync.update  = volume->update_time;
        op->debug_id            = atomic_inc_return(&afs_operation_debug_counter);
        op->nr_iterations       = -1;
        afs_op_set_error(op, -EDESTADDRREQ);

        _leave(" = [op=%08x]", op->debug_id);
        return op;
}

struct afs_io_locker {
        struct list_head        link;
        struct task_struct      *task;
        unsigned long           have_lock;
};

/*
 * Unlock the I/O lock on a vnode.
 */
static void afs_unlock_for_io(struct afs_vnode *vnode)
{
        struct afs_io_locker *locker;

        spin_lock(&vnode->lock);
        locker = list_first_entry_or_null(&vnode->io_lock_waiters,
                                          struct afs_io_locker, link);
        if (locker) {
                list_del(&locker->link);
                smp_store_release(&locker->have_lock, 1); /* The unlock barrier. */
                smp_mb__after_atomic(); /* Store have_lock before task state */
                wake_up_process(locker->task);
        } else {
                clear_bit(AFS_VNODE_IO_LOCK, &vnode->flags);
        }
        spin_unlock(&vnode->lock);
}

/*
 * Lock the I/O lock on a vnode uninterruptibly.  We can't use an ordinary
 * mutex as lockdep will complain if we unlock it in the wrong thread.
 */
static void afs_lock_for_io(struct afs_vnode *vnode)
{
        struct afs_io_locker myself = { .task = current, };

        spin_lock(&vnode->lock);

        if (!test_and_set_bit(AFS_VNODE_IO_LOCK, &vnode->flags)) {
                spin_unlock(&vnode->lock);
                return;
        }

        list_add_tail(&myself.link, &vnode->io_lock_waiters);
        spin_unlock(&vnode->lock);

        for (;;) {
                set_current_state(TASK_UNINTERRUPTIBLE);
                if (smp_load_acquire(&myself.have_lock)) /* The lock barrier */
                        break;
                schedule();
        }
        __set_current_state(TASK_RUNNING);
}

/*
 * Lock the I/O lock on a vnode interruptibly.  We can't use an ordinary mutex
 * as lockdep will complain if we unlock it in the wrong thread.
 */
static int afs_lock_for_io_interruptible(struct afs_vnode *vnode)
{
        struct afs_io_locker myself = { .task = current, };
        int ret = 0;

        spin_lock(&vnode->lock);

        if (!test_and_set_bit(AFS_VNODE_IO_LOCK, &vnode->flags)) {
                spin_unlock(&vnode->lock);
                return 0;
        }

        list_add_tail(&myself.link, &vnode->io_lock_waiters);
        spin_unlock(&vnode->lock);

        for (;;) {
                set_current_state(TASK_INTERRUPTIBLE);
                if (smp_load_acquire(&myself.have_lock) || /* The lock barrier */
                    signal_pending(current))
                        break;
                schedule();
        }
        __set_current_state(TASK_RUNNING);

        /* If we got a signal, try to transfer the lock onto the next
         * waiter.
         */
        if (unlikely(signal_pending(current))) {
                spin_lock(&vnode->lock);
                if (myself.have_lock) {
                        spin_unlock(&vnode->lock);
                        afs_unlock_for_io(vnode);
                } else {
                        list_del(&myself.link);
                        spin_unlock(&vnode->lock);
                }
                ret = -ERESTARTSYS;
        }
        return ret;
}

/*
 * Lock the vnode(s) being operated upon.
 */
static bool afs_get_io_locks(struct afs_operation *op)
{
        struct afs_vnode *vnode = op->file[0].vnode;
        struct afs_vnode *vnode2 = op->file[1].vnode;

        _enter("");

        if (op->flags & AFS_OPERATION_UNINTR) {
                afs_lock_for_io(vnode);
                op->flags |= AFS_OPERATION_LOCK_0;
                _leave(" = t [1]");
                return true;
        }

        if (!vnode2 || !op->file[1].need_io_lock || vnode == vnode2)
                vnode2 = NULL;

        if (vnode2 > vnode)
                swap(vnode, vnode2);

        if (afs_lock_for_io_interruptible(vnode) < 0) {
                afs_op_set_error(op, -ERESTARTSYS);
                op->flags |= AFS_OPERATION_STOP;
                _leave(" = f [I 0]");
                return false;
        }
        op->flags |= AFS_OPERATION_LOCK_0;

        if (vnode2) {
                if (afs_lock_for_io_interruptible(vnode2) < 0) {
                        afs_op_set_error(op, -ERESTARTSYS);
                        op->flags |= AFS_OPERATION_STOP;
                        afs_unlock_for_io(vnode);
                        op->flags &= ~AFS_OPERATION_LOCK_0;
                        _leave(" = f [I 1]");
                        return false;
                }
                op->flags |= AFS_OPERATION_LOCK_1;
        }

        _leave(" = t [2]");
        return true;
}

static void afs_drop_io_locks(struct afs_operation *op)
{
        struct afs_vnode *vnode = op->file[0].vnode;
        struct afs_vnode *vnode2 = op->file[1].vnode;

        _enter("");

        if (op->flags & AFS_OPERATION_LOCK_1)
                afs_unlock_for_io(vnode2);
        if (op->flags & AFS_OPERATION_LOCK_0)
                afs_unlock_for_io(vnode);
}

static void afs_prepare_vnode(struct afs_operation *op, struct afs_vnode_param *vp,
                              unsigned int index)
{
        struct afs_vnode *vnode = vp->vnode;

        if (vnode) {
                vp->fid                 = vnode->fid;
                vp->dv_before           = vnode->status.data_version;
                vp->cb_break_before     = afs_calc_vnode_cb_break(vnode);
                if (vnode->lock_state != AFS_VNODE_LOCK_NONE)
                        op->flags       |= AFS_OPERATION_CUR_ONLY;
                if (vp->modification)
                        set_bit(AFS_VNODE_MODIFYING, &vnode->flags);
        }

        if (vp->fid.vnode)
                _debug("PREP[%u] {%llx:%llu.%u}",
                       index, vp->fid.vid, vp->fid.vnode, vp->fid.unique);
}

/*
 * Begin an operation on the fileserver.
 *
 * Fileserver operations are serialised on the server by vnode, so we serialise
 * them here also using the io_lock.
 */
bool afs_begin_vnode_operation(struct afs_operation *op)
{
        struct afs_vnode *vnode = op->file[0].vnode;

        ASSERT(vnode);

        _enter("");

        if (op->file[0].need_io_lock)
                if (!afs_get_io_locks(op))
                        return false;

        afs_prepare_vnode(op, &op->file[0], 0);
        afs_prepare_vnode(op, &op->file[1], 1);
        op->cb_v_break = atomic_read(&op->volume->cb_v_break);
        _leave(" = true");
        return true;
}

/*
 * Tidy up a filesystem cursor and unlock the vnode.
 */
void afs_end_vnode_operation(struct afs_operation *op)
{
        _enter("");

        switch (afs_op_error(op)) {
        case -EDESTADDRREQ:
        case -EADDRNOTAVAIL:
        case -ENETUNREACH:
        case -EHOSTUNREACH:
                afs_dump_edestaddrreq(op);
                break;
        }

        afs_drop_io_locks(op);
}

/*
 * Wait for an in-progress operation to complete.
 */
void afs_wait_for_operation(struct afs_operation *op)
{
        _enter("");

        while (afs_select_fileserver(op)) {
                op->call_responded = false;
                op->call_error = 0;
                op->call_abort_code = 0;
                if (test_bit(AFS_SERVER_FL_IS_YFS, &op->server->flags) &&
                    op->ops->issue_yfs_rpc)
                        op->ops->issue_yfs_rpc(op);
                else if (op->ops->issue_afs_rpc)
                        op->ops->issue_afs_rpc(op);
                else
                        op->call_error = -ENOTSUPP;

                if (op->call) {
                        afs_wait_for_call_to_complete(op->call);
                        op->call_abort_code = op->call->abort_code;
                        op->call_error = op->call->error;
                        op->call_responded = op->call->responded;
                        afs_put_call(op->call);
                }
        }

        if (op->call_responded && op->server)
                set_bit(AFS_SERVER_FL_RESPONDING, &op->server->flags);

        if (!afs_op_error(op)) {
                _debug("success");
                op->ops->success(op);
        } else if (op->cumul_error.aborted) {
                if (op->ops->aborted)
                        op->ops->aborted(op);
        } else {
                if (op->ops->failed)
                        op->ops->failed(op);
        }

        afs_end_vnode_operation(op);

        if (!afs_op_error(op) && op->ops->edit_dir) {
                _debug("edit_dir");
                op->ops->edit_dir(op);
        }
        _leave("");
}

/*
 * Dispose of an operation.
 */
int afs_put_operation(struct afs_operation *op)
{
        struct afs_addr_list *alist;
        int i, ret = afs_op_error(op);

        _enter("op=%08x,%d", op->debug_id, ret);

        if (op->ops && op->ops->put)
                op->ops->put(op);
        if (op->file[0].modification)
                clear_bit(AFS_VNODE_MODIFYING, &op->file[0].vnode->flags);
        if (op->file[1].modification && op->file[1].vnode != op->file[0].vnode)
                clear_bit(AFS_VNODE_MODIFYING, &op->file[1].vnode->flags);
        if (op->file[0].put_vnode)
                iput(&op->file[0].vnode->netfs.inode);
        if (op->file[1].put_vnode)
                iput(&op->file[1].vnode->netfs.inode);

        if (op->more_files) {
                for (i = 0; i < op->nr_files - 2; i++)
                        if (op->more_files[i].put_vnode)
                                iput(&op->more_files[i].vnode->netfs.inode);
                kfree(op->more_files);
        }

        if (op->estate) {
                alist = op->estate->addresses;
                if (alist) {
                        if (op->call_responded &&
                            op->addr_index != alist->preferred &&
                            test_bit(alist->preferred, &op->addr_tried))
                                WRITE_ONCE(alist->preferred, op->addr_index);
                }
        }

        afs_clear_server_states(op);
        afs_put_serverlist(op->net, op->server_list);
        afs_put_volume(op->volume, afs_volume_trace_put_put_op);
        key_put(op->key);
        kfree(op);
        return ret;
}

int afs_do_sync_operation(struct afs_operation *op)
{
        afs_begin_vnode_operation(op);
        afs_wait_for_operation(op);
        return afs_put_operation(op);
}