FreeBSD/Linux Kernel Cross Reference
sys/fs/ntfs/aops.h

     /**
      * 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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