text: /*-
   * Copyright (c) 2011 The FreeBSD Foundation
   * Copyright (c) 2014-2020 François Tigeot <ftigeot@wolfpond.org>
   * All rights reserved.
   *
   * Portions of this software were developed by Konstantin Belousov
   * under sponsorship from the FreeBSD Foundation.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   *
   */
  
  #include <vm/vm.h>
  #include <vm/vm_page.h>
  #include <vm/vm_page2.h>
  #include <vm/vm_pager.h>
  
  #include <linux/err.h>
  #include <linux/shmem_fs.h>
  
  /*
   * This code is typically called with a normal VM object to access
   * data from a userspace shared memory mapping.  However, handle the
   * case where it might be called with OBJT_MGTDEVICE anyway.
   */
  struct page *
  shmem_read_mapping_page(vm_object_t object, vm_pindex_t pindex)
  {
  	vm_page_t m;
  	int rv;
  
  	VM_OBJECT_LOCK(object);
  	if (object->type == OBJT_MGTDEVICE) {
  		m = NULL;
  		rv = vm_pager_get_page(object, pindex, &m, 1);
  		if (m == NULL)
  			return ERR_PTR(-ENOMEM);
  		if (rv != VM_PAGER_OK) {
  			vm_page_free(m);
  			return ERR_PTR(-ENOMEM);
  		}
  	} else {
  		m = vm_page_grab(object, pindex,
  				 VM_ALLOC_NORMAL | VM_ALLOC_RETRY);
  		if (m->valid != VM_PAGE_BITS_ALL) {
  			if (vm_pager_has_page(object, pindex)) {
  				rv = vm_pager_get_page(object, pindex, &m, 1);
  				m = vm_page_lookup(object, pindex);
  				if (m == NULL)
  					return ERR_PTR(-ENOMEM);
  				if (rv != VM_PAGER_OK) {
  					vm_page_free(m);
  					return ERR_PTR(-ENOMEM);
  				}
  			} else {
  				pmap_zero_page(VM_PAGE_TO_PHYS(m));
  				m->valid = VM_PAGE_BITS_ALL;
  				m->dirty = 0;
  			}
  		}
  	}
  	vm_page_wire(m);		/* put_page() undoes this */
  	vm_page_wakeup(m);
  	VM_OBJECT_UNLOCK(object);
  
  	return (struct page *)m;
  }
  
  struct page *
  shmem_read_mapping_page_gfp(struct vm_object *mapping,
      pgoff_t index, gfp_t gfp_mask)
  {
  	return shmem_read_mapping_page(mapping, index);
  }
  
  #include <linux/fs.h>
  
  int
  pagecache_write_begin(struct vm_object *obj, struct address_space *mapping,
      loff_t pos, unsigned len, unsigned flags, struct page **pagep, void **fsdata)
  {
  	*pagep = shmem_read_mapping_page(obj, OFF_TO_IDX(pos));
  
  	return 0;
  }
  
  /* This is really shmem_write_end() for the i915 gem code */
  int
  pagecache_write_end(struct vm_object *obj, struct address_space *mapping,
      loff_t pos, unsigned len, unsigned copied, struct page *page, void *fsdata)
  {
  	set_page_dirty(page);
  	put_page(page);
  
  	return copied;
  }
  
  