1/*
2 *	linux/mm/filemap.h
3 *
4 * Copyright (C) 1994-1999  Linus Torvalds
5 */
6
7#ifndef __FILEMAP_H
8#define __FILEMAP_H
9
10#include <linux/types.h>
11#include <linux/fs.h>
12#include <linux/mm.h>
13#include <linux/highmem.h>
14#include <linux/uio.h>
15#include <linux/uaccess.h>
16
17size_t
18__filemap_copy_from_user_iovec_inatomic(char *vaddr,
19					const struct iovec *iov,
20					size_t base,
21					size_t bytes);
22
23/*
24 * Copy as much as we can into the page and return the number of bytes which
25 * were sucessfully copied.  If a fault is encountered then clear the page
26 * out to (offset+bytes) and return the number of bytes which were copied.
27 *
28 * NOTE: For this to work reliably we really want copy_from_user_inatomic_nocache
29 * to *NOT* zero any tail of the buffer that it failed to copy.  If it does,
30 * and if the following non-atomic copy succeeds, then there is a small window
31 * where the target page contains neither the data before the write, nor the
32 * data after the write (it contains zero).  A read at this time will see
33 * data that is inconsistent with any ordering of the read and the write.
34 * (This has been detected in practice).
35 */
36static inline size_t
37filemap_copy_from_user(struct page *page, unsigned long offset,
38			const char __user *buf, unsigned bytes)
39{
40	char *kaddr;
41	int left;
42
43	kaddr = kmap_atomic(page, KM_USER0);
44	left = __copy_from_user_inatomic_nocache(kaddr + offset, buf, bytes);
45	kunmap_atomic(kaddr, KM_USER0);
46
47	if (left != 0) {
48		/* Do it the slow way */
49		kaddr = kmap(page);
50		left = __copy_from_user_nocache(kaddr + offset, buf, bytes);
51		kunmap(page);
52	}
53	return bytes - left;
54}
55
56/*
57 * This has the same sideeffects and return value as filemap_copy_from_user().
58 * The difference is that on a fault we need to memset the remainder of the
59 * page (out to offset+bytes), to emulate filemap_copy_from_user()'s
60 * single-segment behaviour.
61 */
62static inline size_t
63filemap_copy_from_user_iovec(struct page *page, unsigned long offset,
64			const struct iovec *iov, size_t base, size_t bytes)
65{
66	char *kaddr;
67	size_t copied;
68
69	kaddr = kmap_atomic(page, KM_USER0);
70	copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov,
71							 base, bytes);
72	kunmap_atomic(kaddr, KM_USER0);
73	if (copied != bytes) {
74		kaddr = kmap(page);
75		copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov,
76								 base, bytes);
77		if (bytes - copied)
78			memset(kaddr + offset + copied, 0, bytes - copied);
79		kunmap(page);
80	}
81	return copied;
82}
83
84static inline void
85filemap_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes)
86{
87	const struct iovec *iov = *iovp;
88	size_t base = *basep;
89
90	do {
91		int copy = min(bytes, iov->iov_len - base);
92
93		bytes -= copy;
94		base += copy;
95		if (iov->iov_len == base) {
96			iov++;
97			base = 0;
98		}
99	} while (bytes);
100	*iovp = iov;
101	*basep = base;
102}
103#endif
104