/* AFS filesystem file handling
   *
   * Copyright (C) 2002, 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/kernel.h>
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/fs.h>
  #include <linux/pagemap.h>
  #include <linux/writeback.h>
  #include <linux/gfp.h>
  #include "internal.h"
  
  static int afs_readpage(struct file *file, struct page *page);
  static void afs_invalidatepage(struct page *page, unsigned int offset,
  			       unsigned int length);
  static int afs_releasepage(struct page *page, gfp_t gfp_flags);
  static int afs_launder_page(struct page *page);
  
  static int afs_readpages(struct file *filp, struct address_space *mapping,
  			 struct list_head *pages, unsigned nr_pages);
  
  const struct file_operations afs_file_operations = {
  	.open		= afs_open,
  	.release	= afs_release,
  	.llseek		= generic_file_llseek,
  	.read		= do_sync_read,
  	.write		= do_sync_write,
  	.aio_read	= generic_file_aio_read,
  	.aio_write	= afs_file_write,
  	.mmap		= generic_file_readonly_mmap,
  	.splice_read	= generic_file_splice_read,
  	.fsync		= afs_fsync,
  	.lock		= afs_lock,
  	.flock		= afs_flock,
  };
  
  const struct inode_operations afs_file_inode_operations = {
  	.getattr	= afs_getattr,
  	.setattr	= afs_setattr,
  	.permission	= afs_permission,
  };
  
  const struct address_space_operations afs_fs_aops = {
  	.readpage	= afs_readpage,
  	.readpages	= afs_readpages,
  	.set_page_dirty	= afs_set_page_dirty,
  	.launder_page	= afs_launder_page,
  	.releasepage	= afs_releasepage,
  	.invalidatepage	= afs_invalidatepage,
  	.write_begin	= afs_write_begin,
  	.write_end	= afs_write_end,
  	.writepage	= afs_writepage,
  	.writepages	= afs_writepages,
  };
  
  /*
   * open an AFS file or directory and attach a key to it
   */
  int afs_open(struct inode *inode, struct file *file)
  {
  	struct afs_vnode *vnode = AFS_FS_I(inode);
  	struct key *key;
  	int ret;
  
  	_enter("{%x:%u},", vnode->fid.vid, vnode->fid.vnode);
  
  	key = afs_request_key(vnode->volume->cell);
  	if (IS_ERR(key)) {
  		_leave(" = %ld [key]", PTR_ERR(key));
  		return PTR_ERR(key);
  	}
  
  	ret = afs_validate(vnode, key);
  	if (ret < 0) {
  		_leave(" = %d [val]", ret);
  		return ret;
  	}
  
  	file->private_data = key;
  	_leave(" = 0");
  	return 0;
  }
  
  /*
   * release an AFS file or directory and discard its key
   */
  int afs_release(struct inode *inode, struct file *file)
  {
  	struct afs_vnode *vnode = AFS_FS_I(inode);
  
  	_enter("{%x:%u},", vnode->fid.vid, vnode->fid.vnode);
  
  	key_put(file->private_data);
  	_leave(" = 0");
  	return 0;
  }
  
  #ifdef CONFIG_AFS_FSCACHE
  /*
   * deal with notification that a page was read from the cache
   */
  static void afs_file_readpage_read_complete(struct page *page,
  					    void *data,
  					    int error)
  {
  	_enter("%p,%p,%d", page, data, error);
  
  	/* if the read completes with an error, we just unlock the page and let
  	 * the VM reissue the readpage */
  	if (!error)
  		SetPageUptodate(page);
  	unlock_page(page);
  }
  #endif
  
  /*
   * read page from file, directory or symlink, given a key to use
   */
  int afs_page_filler(void *data, struct page *page)
  {
  	struct inode *inode = page->mapping->host;
  	struct afs_vnode *vnode = AFS_FS_I(inode);
  	struct key *key = data;
  	size_t len;
  	off_t offset;
  	int ret;
  
  	_enter("{%x},{%lu},{%lu}", key_serial(key), inode->i_ino, page->index);
  
  	BUG_ON(!PageLocked(page));
  
  	ret = -ESTALE;
  	if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
  		goto error;
  
  	/* is it cached? */
  #ifdef CONFIG_AFS_FSCACHE
  	ret = fscache_read_or_alloc_page(vnode->cache,
  					 page,
  					 afs_file_readpage_read_complete,
  					 NULL,
  					 GFP_KERNEL);
  #else
  	ret = -ENOBUFS;
  #endif
  	switch (ret) {
  		/* read BIO submitted (page in cache) */
  	case 0:
  		break;
  
  		/* page not yet cached */
  	case -ENODATA:
  		_debug("cache said ENODATA");
  		goto go_on;
  
  		/* page will not be cached */
  	case -ENOBUFS:
  		_debug("cache said ENOBUFS");
  	default:
  	go_on:
  		offset = page->index << PAGE_CACHE_SHIFT;
  		len = min_t(size_t, i_size_read(inode) - offset, PAGE_SIZE);
  
  		/* read the contents of the file from the server into the
  		 * page */
  		ret = afs_vnode_fetch_data(vnode, key, offset, len, page);
  		if (ret < 0) {
  			if (ret == -ENOENT) {
  				_debug("got NOENT from server"
  				       " - marking file deleted and stale");
  				set_bit(AFS_VNODE_DELETED, &vnode->flags);
  				ret = -ESTALE;
  			}
  
  #ifdef CONFIG_AFS_FSCACHE
  			fscache_uncache_page(vnode->cache, page);
  #endif
  			BUG_ON(PageFsCache(page));
  			goto error;
  		}
  
  		SetPageUptodate(page);
  
  		/* send the page to the cache */
  #ifdef CONFIG_AFS_FSCACHE
  		if (PageFsCache(page) &&
  		    fscache_write_page(vnode->cache, page, GFP_KERNEL) != 0) {
  			fscache_uncache_page(vnode->cache, page);
  			BUG_ON(PageFsCache(page));
  		}
  #endif
  		unlock_page(page);
  	}
  
  	_leave(" = 0");
  	return 0;
  
  error:
  	SetPageError(page);
  	unlock_page(page);
  	_leave(" = %d", ret);
  	return ret;
  }
  
  /*
   * read page from file, directory or symlink, given a file to nominate the key
   * to be used
   */
  static int afs_readpage(struct file *file, struct page *page)
  {
  	struct key *key;
  	int ret;
  
  	if (file) {
  		key = file->private_data;
  		ASSERT(key != NULL);
  		ret = afs_page_filler(key, page);
  	} else {
  		struct inode *inode = page->mapping->host;
  		key = afs_request_key(AFS_FS_S(inode->i_sb)->volume->cell);
  		if (IS_ERR(key)) {
  			ret = PTR_ERR(key);
  		} else {
  			ret = afs_page_filler(key, page);
  			key_put(key);
  		}
  	}
  	return ret;
  }
  
  /*
   * read a set of pages
   */
  static int afs_readpages(struct file *file, struct address_space *mapping,
  			 struct list_head *pages, unsigned nr_pages)
  {
  	struct key *key = file->private_data;
  	struct afs_vnode *vnode;
  	int ret = 0;
  
  	_enter("{%d},{%lu},,%d",
  	       key_serial(key), mapping->host->i_ino, nr_pages);
  
  	ASSERT(key != NULL);
  
  	vnode = AFS_FS_I(mapping->host);
  	if (test_bit(AFS_VNODE_DELETED, &vnode->flags)) {
  		_leave(" = -ESTALE");
  		return -ESTALE;
  	}
  
  	/* attempt to read as many of the pages as possible */
  #ifdef CONFIG_AFS_FSCACHE
  	ret = fscache_read_or_alloc_pages(vnode->cache,
  					  mapping,
  					  pages,
  					  &nr_pages,
  					  afs_file_readpage_read_complete,
  					  NULL,
  					  mapping_gfp_mask(mapping));
  #else
  	ret = -ENOBUFS;
  #endif
  
  	switch (ret) {
  		/* all pages are being read from the cache */
  	case 0:
  		BUG_ON(!list_empty(pages));
  		BUG_ON(nr_pages != 0);
  		_leave(" = 0 [reading all]");
  		return 0;
  
  		/* there were pages that couldn't be read from the cache */
  	case -ENODATA:
  	case -ENOBUFS:
  		break;
  
  		/* other error */
  	default:
  		_leave(" = %d", ret);
  		return ret;
  	}
  
  	/* load the missing pages from the network */
  	ret = read_cache_pages(mapping, pages, afs_page_filler, key);
  
  	_leave(" = %d [netting]", ret);
  	return ret;
  }
  
  /*
   * write back a dirty page
   */
  static int afs_launder_page(struct page *page)
  {
  	_enter("{%lu}", page->index);
  
  	return 0;
  }
  
  /*
   * invalidate part or all of a page
   * - release a page and clean up its private data if offset is 0 (indicating
   *   the entire page)
   */
  static void afs_invalidatepage(struct page *page, unsigned int offset,
  			       unsigned int length)
  {
  	struct afs_writeback *wb = (struct afs_writeback *) page_private(page);
  
  	_enter("{%lu},%u,%u", page->index, offset, length);
  
  	BUG_ON(!PageLocked(page));
  
  	/* we clean up only if the entire page is being invalidated */
  	if (offset == 0 && length == PAGE_CACHE_SIZE) {
  #ifdef CONFIG_AFS_FSCACHE
  		if (PageFsCache(page)) {
  			struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
  			fscache_wait_on_page_write(vnode->cache, page);
  			fscache_uncache_page(vnode->cache, page);
  		}
  #endif
  
  		if (PagePrivate(page)) {
  			if (wb && !PageWriteback(page)) {
  				set_page_private(page, 0);
  				afs_put_writeback(wb);
  			}
  
  			if (!page_private(page))
  				ClearPagePrivate(page);
  		}
  	}
  
  	_leave("");
  }
  
  /*
   * release a page and clean up its private state if it's not busy
   * - return true if the page can now be released, false if not
   */
  static int afs_releasepage(struct page *page, gfp_t gfp_flags)
  {
  	struct afs_writeback *wb = (struct afs_writeback *) page_private(page);
  	struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
  
  	_enter("{{%x:%u}[%lu],%lx},%x",
  	       vnode->fid.vid, vnode->fid.vnode, page->index, page->flags,
  	       gfp_flags);
  
  	/* deny if page is being written to the cache and the caller hasn't
  	 * elected to wait */
  #ifdef CONFIG_AFS_FSCACHE
  	if (!fscache_maybe_release_page(vnode->cache, page, gfp_flags)) {
  		_leave(" = F [cache busy]");
  		return 0;
  	}
  #endif
  
  	if (PagePrivate(page)) {
  		if (wb) {
  			set_page_private(page, 0);
  			afs_put_writeback(wb);
  		}
  		ClearPagePrivate(page);
  	}
  
  	/* indicate that the page can be released */
  	_leave(" = T");
  	return 1;
  }