// SPDX-License-Identifier: GPL-2.0-or-later
/* AFS silly rename handling
 *
 * Copyright (C) 2019 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 * - Derived from NFS's sillyrename.
 */

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

static void afs_silly_rename_success(struct afs_operation *op)
{
        _enter("op=%08x", op->debug_id);

        afs_check_dir_conflict(op, &op->file[0]);
        afs_vnode_commit_status(op, &op->file[0]);
}

static void afs_silly_rename_edit_dir(struct afs_operation *op)
{
        struct afs_vnode_param *dvp = &op->file[0];
        struct afs_vnode *dvnode = dvp->vnode;
        struct afs_vnode *vnode = AFS_FS_I(d_inode(op->dentry));
        struct dentry *old = op->dentry;
        struct dentry *new = op->dentry_2;

        spin_lock(&old->d_lock);
        old->d_flags |= DCACHE_NFSFS_RENAMED;
        spin_unlock(&old->d_lock);
        if (dvnode->silly_key != op->key) {
                key_put(dvnode->silly_key);
                dvnode->silly_key = key_get(op->key);
        }

        down_write(&dvnode->validate_lock);
        if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) &&
            dvnode->status.data_version == dvp->dv_before + dvp->dv_delta) {
                afs_edit_dir_remove(dvnode, &old->d_name,
                                    afs_edit_dir_for_silly_0);
                afs_edit_dir_add(dvnode, &new->d_name,
                                 &vnode->fid, afs_edit_dir_for_silly_1);
        }
        up_write(&dvnode->validate_lock);
}

static const struct afs_operation_ops afs_silly_rename_operation = {
        .issue_afs_rpc  = afs_fs_rename,
        .issue_yfs_rpc  = yfs_fs_rename,
        .success        = afs_silly_rename_success,
        .edit_dir       = afs_silly_rename_edit_dir,
};

/*
 * Actually perform the silly rename step.
 */
static int afs_do_silly_rename(struct afs_vnode *dvnode, struct afs_vnode *vnode,
                               struct dentry *old, struct dentry *new,
                               struct key *key)
{
        struct afs_operation *op;

        _enter("%pd,%pd", old, new);

        op = afs_alloc_operation(key, dvnode->volume);
        if (IS_ERR(op))
                return PTR_ERR(op);

        afs_op_set_vnode(op, 0, dvnode);
        afs_op_set_vnode(op, 1, dvnode);
        op->file[0].dv_delta = 1;
        op->file[1].dv_delta = 1;
        op->file[0].update_ctime = true;
        op->file[1].update_ctime = true;

        op->dentry              = old;
        op->dentry_2            = new;
        op->ops                 = &afs_silly_rename_operation;

        trace_afs_silly_rename(vnode, false);
        return afs_do_sync_operation(op);
}

/**
 * afs_sillyrename - Perform a silly-rename of a dentry
 *
 * AFS is stateless and the server doesn't know when the client is holding a
 * file open.  To prevent application problems when a file is unlinked while
 * it's still open, the client performs a "silly-rename".  That is, it renames
 * the file to a hidden file in the same directory, and only performs the
 * unlink once the last reference to it is put.
 *
 * The final cleanup is done during dentry_iput.
 */
int afs_sillyrename(struct afs_vnode *dvnode, struct afs_vnode *vnode,
                    struct dentry *dentry, struct key *key)
{
        static unsigned int sillycounter;
        struct dentry *sdentry = NULL;
        unsigned char silly[16];
        int ret = -EBUSY;

        _enter("");

        /* We don't allow a dentry to be silly-renamed twice. */
        if (dentry->d_flags & DCACHE_NFSFS_RENAMED)
                return -EBUSY;

        sdentry = NULL;
        do {
                int slen;

                dput(sdentry);
                sillycounter++;

                /* Create a silly name.  Note that the ".__afs" prefix is
                 * understood by the salvager and must not be changed.
                 */
                slen = scnprintf(silly, sizeof(silly), ".__afs%04X", sillycounter);
                sdentry = lookup_one_len(silly, dentry->d_parent, slen);

                /* N.B. Better to return EBUSY here ... it could be dangerous
                 * to delete the file while it's in use.
                 */
                if (IS_ERR(sdentry))
                        goto out;
        } while (!d_is_negative(sdentry));

        ihold(&vnode->vfs_inode);

        ret = afs_do_silly_rename(dvnode, vnode, dentry, sdentry, key);
        switch (ret) {
        case 0:
                /* The rename succeeded. */
                set_bit(AFS_VNODE_SILLY_DELETED, &vnode->flags);
                d_move(dentry, sdentry);
                break;
        case -ERESTARTSYS:
                /* The result of the rename is unknown. Play it safe by forcing
                 * a new lookup.
                 */
                d_drop(dentry);
                d_drop(sdentry);
        }

        iput(&vnode->vfs_inode);
        dput(sdentry);
out:
        _leave(" = %d", ret);
        return ret;
}

static void afs_silly_unlink_success(struct afs_operation *op)
{
        _enter("op=%08x", op->debug_id);
        afs_check_dir_conflict(op, &op->file[0]);
        afs_vnode_commit_status(op, &op->file[0]);
        afs_vnode_commit_status(op, &op->file[1]);
        afs_update_dentry_version(op, &op->file[0], op->dentry);
}

static void afs_silly_unlink_edit_dir(struct afs_operation *op)
{
        struct afs_vnode_param *dvp = &op->file[0];
        struct afs_vnode *dvnode = dvp->vnode;

        _enter("op=%08x", op->debug_id);
        down_write(&dvnode->validate_lock);
        if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) &&
            dvnode->status.data_version == dvp->dv_before + dvp->dv_delta)
                afs_edit_dir_remove(dvnode, &op->dentry->d_name,
                                    afs_edit_dir_for_unlink);
        up_write(&dvnode->validate_lock);
}

static const struct afs_operation_ops afs_silly_unlink_operation = {
        .issue_afs_rpc  = afs_fs_remove_file,
        .issue_yfs_rpc  = yfs_fs_remove_file,
        .success        = afs_silly_unlink_success,
        .aborted        = afs_check_for_remote_deletion,
        .edit_dir       = afs_silly_unlink_edit_dir,
};

/*
 * Tell the server to remove a sillyrename file.
 */
static int afs_do_silly_unlink(struct afs_vnode *dvnode, struct afs_vnode *vnode,
                               struct dentry *dentry, struct key *key)
{
        struct afs_operation *op;

        _enter("");

        op = afs_alloc_operation(NULL, dvnode->volume);
        if (IS_ERR(op))
                return PTR_ERR(op);

        afs_op_set_vnode(op, 0, dvnode);
        afs_op_set_vnode(op, 1, vnode);
        op->file[0].dv_delta = 1;
        op->file[0].update_ctime = true;
        op->file[1].op_unlinked = true;
        op->file[1].update_ctime = true;

        op->dentry      = dentry;
        op->ops         = &afs_silly_unlink_operation;

        trace_afs_silly_rename(vnode, true);
        afs_begin_vnode_operation(op);
        afs_wait_for_operation(op);

        /* If there was a conflict with a third party, check the status of the
         * unlinked vnode.
         */
        if (op->error == 0 && (op->flags & AFS_OPERATION_DIR_CONFLICT)) {
                op->file[1].update_ctime = false;
                op->fetch_status.which = 1;
                op->ops = &afs_fetch_status_operation;
                afs_begin_vnode_operation(op);
                afs_wait_for_operation(op);
        }

        return afs_put_operation(op);
}

/*
 * Remove sillyrename file on iput.
 */
int afs_silly_iput(struct dentry *dentry, struct inode *inode)
{
        struct afs_vnode *dvnode = AFS_FS_I(d_inode(dentry->d_parent));
        struct afs_vnode *vnode = AFS_FS_I(inode);
        struct dentry *alias;
        int ret;

        DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);

        _enter("%p{%pd},%llx", dentry, dentry, vnode->fid.vnode);

        down_read(&dvnode->rmdir_lock);

        alias = d_alloc_parallel(dentry->d_parent, &dentry->d_name, &wq);
        if (IS_ERR(alias)) {
                up_read(&dvnode->rmdir_lock);
                return 0;
        }

        if (!d_in_lookup(alias)) {
                /* We raced with lookup...  See if we need to transfer the
                 * sillyrename information to the aliased dentry.
                 */
                ret = 0;
                spin_lock(&alias->d_lock);
                if (d_really_is_positive(alias) &&
                    !(alias->d_flags & DCACHE_NFSFS_RENAMED)) {
                        alias->d_flags |= DCACHE_NFSFS_RENAMED;
                        ret = 1;
                }
                spin_unlock(&alias->d_lock);
                up_read(&dvnode->rmdir_lock);
                dput(alias);
                return ret;
        }

        /* Stop lock-release from complaining. */
        spin_lock(&vnode->lock);
        vnode->lock_state = AFS_VNODE_LOCK_DELETED;
        trace_afs_flock_ev(vnode, NULL, afs_flock_silly_delete, 0);
        spin_unlock(&vnode->lock);

        afs_do_silly_unlink(dvnode, vnode, dentry, dvnode->silly_key);
        up_read(&dvnode->rmdir_lock);
        d_lookup_done(alias);
        dput(alias);
        return 1;
}