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/**
* aops.h - Defines for NTFS kernel address space operations and page cache
* handling. Part of the Linux-NTFS project.
*
* Copyright (c) 2001-2004 Anton Altaparmakov
* Copyright (c) 2002 Richard Russon
*
* This program/include file 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.
*
* This program/include file is distributed in the hope that it will be
* useful, but WITHOUT ANY WARRANTY; without even the implied warranty
* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program (in the main directory of the Linux-NTFS
* distribution in the file COPYING); if not, write to the Free Software
* Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#ifndef _LINUX_NTFS_AOPS_H
#define _LINUX_NTFS_AOPS_H
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/fs.h>
#include "inode.h"
/**
* ntfs_unmap_page - release a page that was mapped using ntfs_map_page()
* @page: the page to release
*
* Unpin, unmap and release a page that was obtained from ntfs_map_page().
*/
static inline void ntfs_unmap_page(struct page *page)
{
kunmap(page);
page_cache_release(page);
}
/**
* ntfs_map_page - map a page into accessible memory, reading it if necessary
* @mapping: address space for which to obtain the page
* @index: index into the page cache for @mapping of the page to map
*
* Read a page from the page cache of the address space @mapping at position
* @index, where @index is in units of PAGE_CACHE_SIZE, and not in bytes.
*
* If the page is not in memory it is loaded from disk first using the readpage
* method defined in the address space operations of @mapping and the page is
* added to the page cache of @mapping in the process.
*
* If the page belongs to an mst protected attribute and it is marked as such
* in its ntfs inode (NInoMstProtected()) the mst fixups are applied but no
* error checking is performed. This means the caller has to verify whether
* the ntfs record(s) contained in the page are valid or not using one of the
* ntfs_is_XXXX_record{,p}() macros, where XXXX is the record type you are
* expecting to see. (For details of the macros, see fs/ntfs/layout.h.)
*
* If the page is in high memory it is mapped into memory directly addressible
* by the kernel.
*
* Finally the page count is incremented, thus pinning the page into place.
*
* The above means that page_address(page) can be used on all pages obtained
* with ntfs_map_page() to get the kernel virtual address of the page.
*
* When finished with the page, the caller has to call ntfs_unmap_page() to
* unpin, unmap and release the page.
*
* Note this does not grant exclusive access. If such is desired, the caller
* must provide it independently of the ntfs_{un}map_page() calls by using
* a {rw_}semaphore or other means of serialization. A spin lock cannot be
* used as ntfs_map_page() can block.
*
* The unlocked and uptodate page is returned on success or an encoded error
* on failure. Caller has to test for error using the IS_ERR() macro on the
* return value. If that evaluates to 'true', the negative error code can be
* obtained using PTR_ERR() on the return value of ntfs_map_page().
*/
static inline struct page *ntfs_map_page(struct address_space *mapping,
unsigned long index)
{
struct page *page = read_mapping_page(mapping, index, NULL);
if (!IS_ERR(page)) {
kmap(page);
if (!PageError(page))
return page;
ntfs_unmap_page(page);
return ERR_PTR(-EIO);
}
return page;
}
#ifdef NTFS_RW
extern void mark_ntfs_record_dirty(struct page *page, const unsigned int ofs);
#endif /* NTFS_RW */
#endif /* _LINUX_NTFS_AOPS_H */
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