108 lines
3.9 KiB
C
108 lines
3.9 KiB
C
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/**
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* aops.h - Defines for NTFS kernel address space operations and page cache
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* handling. Part of the Linux-NTFS project.
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*
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* Copyright (c) 2001-2004 Anton Altaparmakov
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* Copyright (c) 2002 Richard Russon
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*
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* This program/include file is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as published
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* by the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program/include file is distributed in the hope that it will be
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* useful, but WITHOUT ANY WARRANTY; without even the implied warranty
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* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program (in the main directory of the Linux-NTFS
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* distribution in the file COPYING); if not, write to the Free Software
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* Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#ifndef _LINUX_NTFS_AOPS_H
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#define _LINUX_NTFS_AOPS_H
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#include <linux/mm.h>
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#include <linux/highmem.h>
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#include <linux/pagemap.h>
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#include <linux/fs.h>
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#include "inode.h"
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/**
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* ntfs_unmap_page - release a page that was mapped using ntfs_map_page()
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* @page: the page to release
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*
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* Unpin, unmap and release a page that was obtained from ntfs_map_page().
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*/
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static inline void ntfs_unmap_page(struct page *page)
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{
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kunmap(page);
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page_cache_release(page);
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}
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/**
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* ntfs_map_page - map a page into accessible memory, reading it if necessary
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* @mapping: address space for which to obtain the page
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* @index: index into the page cache for @mapping of the page to map
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*
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* Read a page from the page cache of the address space @mapping at position
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* @index, where @index is in units of PAGE_CACHE_SIZE, and not in bytes.
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*
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* If the page is not in memory it is loaded from disk first using the readpage
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* method defined in the address space operations of @mapping and the page is
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* added to the page cache of @mapping in the process.
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*
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* If the page belongs to an mst protected attribute and it is marked as such
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* in its ntfs inode (NInoMstProtected()) the mst fixups are applied but no
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* error checking is performed. This means the caller has to verify whether
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* the ntfs record(s) contained in the page are valid or not using one of the
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* ntfs_is_XXXX_record{,p}() macros, where XXXX is the record type you are
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* expecting to see. (For details of the macros, see fs/ntfs/layout.h.)
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*
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* If the page is in high memory it is mapped into memory directly addressible
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* by the kernel.
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*
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* Finally the page count is incremented, thus pinning the page into place.
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*
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* The above means that page_address(page) can be used on all pages obtained
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* with ntfs_map_page() to get the kernel virtual address of the page.
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*
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* When finished with the page, the caller has to call ntfs_unmap_page() to
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* unpin, unmap and release the page.
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*
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* Note this does not grant exclusive access. If such is desired, the caller
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* must provide it independently of the ntfs_{un}map_page() calls by using
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* a {rw_}semaphore or other means of serialization. A spin lock cannot be
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* used as ntfs_map_page() can block.
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*
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* The unlocked and uptodate page is returned on success or an encoded error
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* on failure. Caller has to test for error using the IS_ERR() macro on the
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* return value. If that evaluates to 'true', the negative error code can be
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* obtained using PTR_ERR() on the return value of ntfs_map_page().
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*/
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static inline struct page *ntfs_map_page(struct address_space *mapping,
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unsigned long index)
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{
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struct page *page = read_mapping_page(mapping, index, NULL);
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if (!IS_ERR(page)) {
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kmap(page);
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if (!PageError(page))
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return page;
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ntfs_unmap_page(page);
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return ERR_PTR(-EIO);
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}
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return page;
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}
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#ifdef NTFS_RW
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extern void mark_ntfs_record_dirty(struct page *page, const unsigned int ofs);
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#endif /* NTFS_RW */
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#endif /* _LINUX_NTFS_AOPS_H */
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